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Chapter 7/Application of Traffic Control Devices Page 7-1 Roundabouts: An Informational Guide CHAPTER 7 APPLICATION OF TRAFFIC CONTROL DEVICES CONTENTS 7.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-4 7.2 PRINCIPLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-4 7.3 PAVEMENT MARKINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-5 7.3.1 Approach and Departure Pavement Markings . . . . . . . . . . . . . . . . . 7-5 7.3.2 Circulatory Roadway Pavement Markings . . . . . . . . . . . . . . . . . . . 7-13 7.3.3 Mini-Roundabout Pavement Markings . . . . . . . . . . . . . . . . . . . . . . 7-16 7.4 SIGNING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-17 7.4.1 Regulatory Signs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-18 7.4.2 Warning Signs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-21 7.4.3 Guide Signs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-23 7.4.4 Supplemental Treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-29 7.5 SIGNALIZATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-31 7.5.1 Metering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-31 7.5.2 Pedestrian Signals at Roundabouts . . . . . . . . . . . . . . . . . . . . . . . . . . 7-33 7.5.3 Signal Mounting Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-37 7.5.4 Full Signalization of the Circulatory Roadway . . . . . . . . . . . . . . . . 7-38 7.6 AT-GRADE RAIL CROSSINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-38 7.7 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-42
Roundabouts: An Informational Guide Page 7-2 Chapter 7/Application of Traffic Control Devices LIST OF EXHIBITS Exhibit 7-1 Approach and Departure Pavement Markings . . . . . . . . . . . . . . . . . 7-6 Exhibit 7-2 Vane Island between Entry Lanes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7 Exhibit 7-3 Lane-Use Arrow Options for Roundabout Approaches . . . . . . . . . . 7-8 Exhibit 7-4 Yield Ahead Marking Placement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-10 Exhibit 7-5 Roundabout Entrance Pavement Markings . . . . . . . . . . . . . . . . . . . 7-11 Exhibit 7-6 Example of Staggered Yield Line on a Multilane Approach . . . . . 7-11 Exhibit 7-7 Typical Crosswalk Markings on a Roundabout Approach . . . . . . 7-12 Exhibit 7-8 Circulatory Roadway Markings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-13 Exhibit 7-9 Circulatory Roadway Lane Line Pattern Using Solid and Dotted Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-15 Exhibit 7-10 Alternative Circulatory Roadway Lane Line Pattern Using a Uniform Dotted Line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-15 Exhibit 7-11 Example Markings for a Mini-Roundabout . . . . . . . . . . . . . . . . . . 7-17 Exhibit 7-12 Roundabout Directional Arrow Signs (R6-4, R6-4a, and R6-4b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-18 Exhibit 7-13 One-Way Sign (R6-1R) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-18 Exhibit 7-14 Roundabout Circulation Plaque (R6-5P) . . . . . . . . . . . . . . . . . . . . . 7-19 Exhibit 7-15 Intersection Lane-Control Signing Options for a Roundabout Approach with Double Left-Turn Lanes . . . . . . . . . 7-20 Exhibit 7-16 Intersection Lane-Control Sign Arrow Options for Roundabouts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-20 Exhibit 7-17 Circular Intersection Sign (W2-6) . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-22 Exhibit 7-18 Example of Regulatory and Warning Signs for Mini-Roundabouts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-24 Exhibit 7-19 Example of Regulatory and Warning Signs for Single-Lane Roundabouts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-25 Exhibit 7-20 Example of Regulatory and Warning Signs for a Two-Lane Roundabout with Consecutive Double Left Turns . . . 7-26 Exhibit 7-21 Exit Destination Signs with Text and Arrows . . . . . . . . . . . . . . . . . 7-27 Exhibit 7-22 Diagrammatic Exit Destination Sign . . . . . . . . . . . . . . . . . . . . . . . . 7-27 Exhibit 7-23 Advance Street Name Sign for Use at Roundabouts (D3-2) . . . . . 7-28 Exhibit 7-24 Exit Guide Signs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-28 Exhibit 7-25 Example Sign Layout for Guide Signs at Roundabouts . . . . . . . . 7-29 Exhibit 7-26 Internally Illuminated Bollard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-30 Exhibit 7-27 Examples of Speed Reduction Treatments . . . . . . . . . . . . . . . . . . . 7-30 Exhibit 7-28 Example Diagram Showing Metering Signal Operation in Clearwater, Florida . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-32
Chapter 7/Application of Traffic Control Devices Page 7-3 Roundabouts: An Informational Guide Exhibit 7-29 Examples of Metering Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-32 Exhibit 7-30 Pedestrian Signal Placement at Angled Crosswalk . . . . . . . . . . . . 7-34 Exhibit 7-31 Pedestrian Signal Placement at Staggered Crosswalk . . . . . . . . . . 7-35 Exhibit 7-32 Display Sequence for a Pedestrian Hybrid Beacon . . . . . . . . . . . . 7-36 Exhibit 7-33 Examples of Warning Beacons at Pedestrian Crossings . . . . . . . . 7-37 Exhibit 7-34 Rail Crossing One Leg of the Intersection . . . . . . . . . . . . . . . . . . . . 7-40 Exhibit 7-35 Rail Crossing through Center of Roundabout . . . . . . . . . . . . . . . . 7-41 Exhibit 7-36 Rail Running down Roadway Median . . . . . . . . . . . . . . . . . . . . . . 7-42
Roundabouts: An Informational Guide Page 7-4 Chapter 7/Application of Traffic Control Devices 7.1 INTRODUCTION This chapter presents guidelines on the application of traffic control devices associated with roundabouts. The design installation of these elements is an important component in achieving the desired operational and safety features of a roundabout. The Manual on Uniform Traffic Control Devices for Streets and Highways (1), the latest version of FHWAâs Standard Highway Signs, and any applicable state and local standards govern the design and placement of traffic control devices, includ- ing signs, pavement markings, and signals. This chapter is intended to reflect the state of the practice for signing, marking, and use of other traffic control devices for roundabouts; however, the MUTCD and any relevant state and local policies supersede the guidance of this chapter in the event of a conflict. A variety of photos are provided within this chapter to illustrate specific signs, markings, or other traffic control features. Inclusion of these photos does not constitute an endorsement of the geometric features captured, which are not the subject of the photo. Additionally, some photos may contain traffic control devices that reflect the practice of their time and may no longer reflect current practice. 7.2 PRINCIPLES At roundabouts, pavement markings and signs work together to create a com- prehensive system to guide and regulate road users. For signs and pavement markings at roundabouts to provide appropriate guidance, the following general principles should be considered: â¢ Markings and signs are integral to the design of roundabouts, especially for multilane roundabouts. Markings, in particular, need to be considered during the preliminary design stages, rather than fitting them in later in the design process. â¢ Markings and signs complement the geometric design of the roundabout. They clarify the rules of the road to the user, but they do not create the safety characteristics to the extent the geometric design does. â¢ Markings and signs should be compatible with each other to present a con- sistent message to the road user. Likewise, markings on approaches to the roundabout should be compatible with circulatory roadway markings. â¢ Markings and signs should facilitate through and turning movements in a manner such that drivers choose the appropriate lane when approaching a roundabout and then do not need to change lanes within the circulatory roadway before exiting in their desired direction. â¢ Approach markings should provide adequate time and distance for approaching drivers to select the appropriate lane for their desired exit.
Chapter 7/Application of Traffic Control Devices Page 7-5 Roundabouts: An Informational Guide These principles also extend to the designation of lanes on approaches to roundabouts: â¢ Traffic volume considerations and roundabout operations. Roundabouts should be designed with the appropriate number and assignment of lanes to han- dle the expected through, left-turning, and right-turning traffic. This may require more than one lane to handle the expected demand for some movements and may also require that some lanes be used for multiple movements (see Chapter 4). â¢ Balanced lane use. Lane use should be balanced as much as practical. In some situations, certain lane designations (or the lack thereof) may result in the overuse of some lanes for certain movements, resulting in unneces- sarily long queues and congestion This can also result in reduced safety as motorists try to bypass congestion by choosing inappropriate lanes for their desired movements. This is challenging when traffic patterns vary widely throughout the day. â¢ Exit lane requirements. The number of exit lanes provided should be the minimum required to handle the expected exit volume. However, drivers have a reasonable expectation that there will be an exit lane to receive each corresponding entry lane (e.g., two exit lanes to receive a double left turn). 7.3 PAVEMENT MARKINGS Typical pavement markings for roundabouts delineate the entries, exits, and the circulatory roadway, providing guidance for pedestrians and vehicle opera- tors. This section discusses the application of some of the more relevant pavement markings at roundabouts. Example pavement marking layouts for a variety of lane configurations are given in Appendix A. 7.3.1 APPROACH AND DEPARTURE PAVEMENT MARKINGS Approach and departure pavement markings consist of lane lines, edge lines, lane-use arrows, other pavement word and symbol markings, yield lines, and crosswalk markings. Exhibit 7-1 shows typical approach and departure pavement markings. The following sections discuss these in more detail. 188.8.131.52 Centerlines and Edge Lines Typically, yellow edge lines should be provided along splitter islands at the left edge of the approach and departure roadways and at the left edge of right- turn bypass roadways to enhance driver recognition of the changing roadway. Optionally, edge stripes may be omitted along splitter islands, allowing the islands themselves to provide edge delineation. Double yellow centerline markings representing a two-direction no-passing zone should be used on undivided roadways on the approach to the splitter islands. Immediately before the splitter island the double yellow centerline markings should split into two double yellow markings, creating a taper to the raised splitter island. Yellow diagonal markings may be placed in the neutral area between the two sets of
Roundabouts: An Informational Guide Page 7-6 Chapter 7/Application of Traffic Control Devices double yellow lines. For small splitter islands [area less than 75 ft2 (7 m2)], the island may consist of pavement markings only, in the form of two sets of double yellow lines or marking the entire splitter island yellow. However, raised splitter islands should be used where possible. White edge line markings may be used along the right side of the approach and departure roadways adjacent to the outside curb. White edge line markings should be used along the right side of approach and departure roadways adjacent to right- turn bypass islands to enhance driver recognition of the changing roadway. Raised pavement markers may be used to supplement edge lines. These provide additional visibility at night and in inclement weather. However, they increase maintenance costs and can be troublesome in areas requiring frequent snow removal. In addition, raised pavement markers should not be used in the path of travel of bicyclists. 184.108.40.206 Lane Lines As indicated in the MUTCD, white lane line markings should be used on multilane approaches. White lane lines should also be used on multilane depar- tures. Solid white lane lines are recommended on roundabout approaches and departures to discourage lane changes in the immediate vicinity of the round- about, as shown in Exhibit 7-1. Solid lane lines provide the following benefits: â¢ As at traditional signalized intersections, solid lane lines on approaches can improve safety by reducing the likelihood of sideswipe crashes caused by last-minute lane changes. Exhibit 7-1 Approach and Departure Pavement Markings Solid white lane lines are recommended on roundabout approaches and departures.
Chapter 7/Application of Traffic Control Devices Page 7-7 Roundabouts: An Informational Guide â¢ Solid lane lines on approaches and departures can discourage drivers from cutting across multiple lanes to attain a faster path through the roundabout. Using solid lane lines throughout the area of deflection can be used to provide this benefit. â¢ Solid lane lines can be used to discourage lane changes immediately before crosswalks to reduce the likelihood of multiple-threat crashes between vehicles and pedestrians. On flared approaches to roundabouts, the lane lines in the flared section should extend back as far from the circulatory roadway as possible. For example, when flaring from one to two lanes, as soon as there is paved entry width of 20 ft (6 m) available, the lane line should begin, creating two 10-ft (3-m) approach lanes that will typically continue to widen approaching the circulatory roadway. White channelizing lines are recommended on the approach to and depar- ture from right-turn bypass islands, where traffic passes on both sides of the islands. Some agencies have used channelizing lines to create painted islands between entry lanes, sometimes called âvane islands.â These islands, shown in Exhibit 7-2, are believed to assist with deflecting entering vehicles to the appro- priate position within the circulatory roadway while providing an overrun area for larger vehicles. White chevron markings may be placed in the neutral area between the channelizing lines. Exhibit 7-2 Vane Island between Entry Lanes Bicycle lane markings should be terminated in advance of the circulatory roadway. Wisconsin 220.127.116.11 Bicycle Lane Markings Where bicycle lane markings are used on approach roadways, they should be terminated in advance of the circulatory roadway. See Chapter 6 for the geometric details for bicycle lanes on the approaches and departures of roundabouts, includ- ing taper rates. On approaches to roundabouts, bicycle lane lines should be terminated as soon as the taper begins and at least 100 ft (30 m) from the edge of the circulatory road- way. The bicycle lane lines should be dotted for the last 50 to 200 ft (15 to 60 m) to
Roundabouts: An Informational Guide Page 7-8 Chapter 7/Application of Traffic Control Devices give advance notice to cyclists that they need to merge, providing more room for them to achieve this maneuver and find an appropriate gap in traffic. On roundabout departures, a dotted line should be used through the diverg- ing taper, and the solid bike lane line should resume as soon as the normal bicycle lane width is available. 18.104.22.168 Lane-Use Arrows Lane-use arrows are one of the major components of the comprehensive sys- tem of signing and marking at roundabouts. On roundabout approaches, lane-use arrows and intersection lane-control signs should complement each other and provide a consistent message to the traveling public. See Section 22.214.171.124 for a discussion of intersection lane-control signs. Lane-use arrows are not necessary on single lane roundabouts. Lane-use arrows can be beneficial on the approaches to any multilane roundabout to assist drivers in selecting the appropriate lane before they enter the roundabout. On a typical two-lane roundabout, where the leftmost entry lane is for left turns and through movements and the rightmost entry lane is for right turns and through movements, approach lane-use arrows are generally not necessary. As round- abouts get more complex, lane-use arrows become increasingly important. Lane- use arrows should be used at roundabout approaches with double left-turn or double right-turn lanes and at other multilane roundabouts where lane-use arrows will improve lane utilization by drivers. Standard lane-use arrows have been used at roundabouts internationally. In the United States, some concern has been raised by individual states regarding the legal interpretation of standard arrows at the entry to a roundabout with respect to whether it promotes turning left into the circulatory roadway. As described in the MUTCD, there are four different options for the design of lane-use arrows on the approach to roundabouts (shown in Exhibit 7-3). As shown on the left, normal lane-use arrows may be used with or without an oval symbolizing the central island. Alternatively, fishhook arrows, as shown on the right, may be used, with or without an oval symbolizing the central island. In choosing a lane-use arrow design, designers should consider the general practices within a city, region, or state. As a cautionary note, the more complex lane-use arrow designs may more Exhibit 7-3 Lane-Use Arrow Options for Roundabout Approaches
Chapter 7/Application of Traffic Control Devices Page 7-9 Roundabouts: An Informational Guide quickly lose their readability when a portion of the marking is worn away by the tires of passing vehicles. Where lane-use arrows are used on roundabout approaches, it is important that left-turn arrows be included. Some practitioners have concerns that left-turn arrows on the approach will encourage drivers to make an improper left turn onto the circu- latory roadway in front of the central island instead of making a proper left turn by circulating around the central island. This concern should not be allowed to override the need to provide appropriate lane-use arrows to encourage proper lane use at roundabouts, which in turn can reduce crashes at roundabout exits. There are several cues to the driver that they should not turn left onto the circulatory roadway, includ- ing the angle of approach to the circulatory roadway, the fact that circulating traffic is in an opposing direction, the signs on the central island that point the correct direction, and lane-use arrows on the circulatory roadway that point the correct direction. The fishhook arrows and the oval symbolizing the central island as shown in Exhibit 7-3 are intended to further mitigate the concern that drivers may mistake the left-turn arrow as directing them to turn left onto the circulatory roadway. The MUTCD requires the use of lane-use arrows on an approach to a round- about where a through lane becomes a left-turn only lane or a right-turn only lane. Lane-use arrows (and corresponding lane-use signs) should be placed as far in advance of the roundabout as practical in order to give drivers plenty of time to select the correct approach lane for their desired exit. Lane-use arrows can be repeated to provide more emphasis and continue to encourage drivers to select the correct approach lane. The set of arrows closest to the roundabout should be provided upstream of the pedestrian crossing, with no arrows provided in the area between the pedestrian crossing and the entrance line. At roundabouts with more than four legs, it can be difficult to select the appropriate lane-use arrows on the approaches. Engineering judgment should be used to choose the appropriate lane-use arrows for each lane. The angle between the entry leg and the possible exit legs should be a major factor in this decision. A good rule of thumb is to designate legs that are less than 150Â° from the entry leg as right-turn movements, legs that are 150Â° to 210Â° from the entry leg as through movements, and legs that are more than 210Â° from the entry leg as left-turn move- ments. Other factors to consider include route continuity (e.g., using a through arrow to connect roadways with the same street name), the volume of traffic mov- ing from the approach leg to each exit leg, and the fact that it might be appropriate to designate two closely spaced exit legs as the same type of movement. For exam- ple, if there is a low volume exit at about 60Â° from the entry leg, and two high- volume exits at 150Â° and 210Â° from the entry leg, it might be desirable to designate the 150Â° leg as a right-turn movement. At some complex roundabouts with many legs, it can be desirable to use other traffic control devices in addition to lane-use arrows to designate the appropriate approach lanes, such as pavement word and symbol markings and advance guide signs indicating destinations for each lane. 126.96.36.199 Pavement Word and Symbol Markings In some cases, the designer may want to consider pavement word or symbol markings to supplement the signing, lane-use arrows, and other markings. These markings should conform to the standards given in the appropriate sections of the Lane-use arrows on roundabout approaches need to include left turn arrows to encourage proper lane use. There are at least four other cues to the driver that they should not turn left onto the circulatory roadway in front of the central island. Pavement word markings are less effective in rainy or especially snowy climates.
Roundabouts: An Informational Guide Page 7-10 Chapter 7/Application of Traffic Control Devices MUTCD (3B.20 and 3C.06). The following types of pavement word and symbol markings can be used at roundabouts: â¢ ONLY word marking. An ONLY word marking may be used to supplement lane-use arrows in lanes that are designated for a single movement. â¢ Route numbers, destinations, street names, and cardinal directions. Pavement markings showing route number destinations, street names, or cardinal directions (NORTH, SOUTH, EAST, or WEST) can be used to assist drivers in selecting the appropriate entry lane on roundabout approaches. These markings would typically be used to supplement lane-use arrows, lane-use signs, and guide signs at roundabouts. At complex roundabouts with many legs, these markings can be especially useful because it can be difficult to adequately communicate appropriate lane use with only lane- use arrows. Route numbers may be shown using numerals and letters (e.g., I-275, US 97, or HWY 22) or by using pavement markings that simu- late Interstate, U.S., State, and other official highway route shield signs, but elongated for proper proportioning when viewed as a marking. Word pavement markings can also spell out destinations, street names, or cardinal directions using elongated letters or numerals. â¢ Yield Ahead symbol or word marking. The yield ahead triangle symbol or YIELD AHEAD word pavement markings are sometimes used on round- about approaches to supplement a Yield Ahead sign, as illustrated in Exhibit 7-4. The yield ahead symbol marking has the advantage of being symbolic and is similar to markings used in other countries; however, this marking has not seen widespread use in the United States to date. â¢ YIELD word marking. A YIELD word pavement marking is sometimes used at a roundabout entrance to supplement the yield sign. This marking is suggested in situations where additional identification of the requirement to yield is desirable, especially where yielding violations have been frequently observed. If used, the YIELD word marking should be placed immediately ahead of the entrance line or the yield line, as illustrated in Exhibit 7-5. Exhibit 7-4 Yield Ahead Marking Placement
Chapter 7/Application of Traffic Control Devices Page 7-11 Roundabouts: An Informational Guide Exhibit 7-5 Roundabout Entrance Pavement Markings Exhibit 7-6 Example of Staggered Yield Line on a Multilane Approach Yield lines can be used to indicate where approaching vehicles should yield, supple- menting the entrance lines. 188.8.131.52 Entrance and Yield Lines Dotted circulatory roadway edge line extensions should be used across the entry lanes of roundabouts, as illustrated in Exhibit 7-5. These edge lines act as entrance lines, marking the boundary between entering and circulating vehicles. The typical marking pattern for these lines can be found in Section 184.108.40.206. Yield lines may be used in addition to entrance lines to further indicate the point behind which vehicles are required to yield in response to the yield signs. As described in MUTCD Section 3B.16, yield lines consist of a row of solid white isosceles triangles pointing toward approaching vehicles. Like other applications of yield lines and stop lines, the yield lines at roundabouts should normally be placed at right angles to the roadway. If used at multilane roundabouts, yield lines should be staggered on a lane-by-lane basis. Staggered yield lines are important at roundabouts so that drivers waiting at the yield line in the right- most lane(s) can more easily see past vehicles waiting in lanes to their left (see Exhibit 7-6).
Roundabouts: An Informational Guide Page 7-12 Chapter 7/Application of Traffic Control Devices 220.127.116.11 Pedestrian Crosswalk Markings Pedestrian crosswalk markings should be installed at all pedestrian crossing locations at roundabouts in urban and suburban locations. Crosswalk markings provide guidance for pedestrians in navigating a roundabout and provide a visual cue to drivers of where pedestrians may be within the roadway. The use of cross- walk markings in this manner is consistent with the MUTCD. As discussed in Chapter 2, without crosswalk markings, the legal status of pedestrian crossings at roundabouts may be unclear, depending on state laws. For this reason, it is important that pedestrian crossings at roundabouts be marked to legally establish the crosswalk. Where the pedestrian crossing location is distin- guished from the roadway by visually contrasting pavement colors and textures, crosswalk markings are still needed to legally establish the crosswalk. In this situ- ation, the colored or textured area should be outlined with simple transverse crosswalk markings. At roundabouts, crosswalk markings that are longitudinal to the flow of traf- fic (known as âZebraâ or âContinentalâ crosswalk markings) are recommended. Details on the dimensions of these markings can be found in MUTCD Section 3B.18. Longitudinal crosswalk markings, illustrated in Exhibit 7-7, have a number of advantages over transverse crosswalk marking in roundabout applications: â¢ The longitudinal markings provide a higher degree of visibility, which is important because the crosswalk is set back from the yield line. â¢ Longitudinal crosswalk lines are less likely to be confused with the entrance line or the yield line. â¢ Although the initial cost is somewhat higher, longitudinal markings require less maintenance if properly spaced to avoid the wheel paths of vehicles. Crosswalk markings should be installed across the entrance and exit of each leg and across any right-turn bypass lanes. The crosswalk should be approxi- mately perpendicular to the flow of vehicular traffic and be aligned with the ramps and pedestrian refuge in the splitter island. Additional geometric design details for pedestrian crossings at roundabouts can be found in Section 6.8. Crosswalks should be marked to provide an important visual cue for drivers and pedestrians and to legally establish the location of the crosswalk set back somewhat from the intersection. Longitudinal crosswalk mark- ings (also known as âZebraâ or âContinentalâ markings) are recommended for use at roundabouts. See Section 6.8 for additional details regarding the design of pedestrian crossings at roundabouts. Exhibit 7-7 Typical Crosswalk Markings on a Roundabout Approach
Chapter 7/Application of Traffic Control Devices Page 7-13 Roundabouts: An Informational Guide 7.3.2 CIRCULATORY ROADWAY PAVEMENT MARKINGS Circulatory roadway pavement markings consist of lane lines, edge lines, and lane-use arrows. Examples of these markings are shown in Exhibit 7-8, and the following sections discuss each of these types of markings in more detail. Circulatory roadway pavement markings are part of the com- prehensive system of signing and marking for roundabouts. Exhibit 7-8 Circulatory Roadway Markings 18.104.22.168 Edge Lines A yellow edge line may be placed around the inside edge of the circulatory roadway along the central island or truck apron. This line should have a width of 4 to 6 in. (100 to 150 mm). Yellow edge lines may also be used to channelize traffic away from the central island toward a specific circulating lane. This channeliza- tion is sometimes necessary to work in concert with lane line markings (see Sec- tion 22.214.171.124) to channelize traffic to the appropriate exit lane. Yellow diagonal markings may be placed in the neutral area between this channelizing edge line and the circulatory roadway. See Exhibit 7-8 for examples of the yellow edge lines described above. The exhibit also illustrates an alternative of extending the truck apron to provide raised channelization. At mini-roundabouts or other round- abouts with fully mountable central islands, the entire central island may be colored yellow in lieu of the yellow edge lines. As described in MUTCD Section 3C.03, white edge line markings should be used on the outer edge of the circulatory roadway of roundabouts. Along the splitter The white dotted edge line extension across the entry lane of a roundabout acts as an entrance line, delineating the circulatory roadway and reducing the need for yield line markings.
Roundabouts: An Informational Guide Page 7-14 Chapter 7/Application of Traffic Control Devices island, a normal-width white line should be used. Wide dotted edge line extensions should be placed across the entry lanes of roundabouts. These edge line extensions are typically 12- to 18-in. (300- to 450-mm) wide and have a typical marking pattern of 2-ft (0.6 m) lines with 2- to 3-ft (0.6 to 0.9 m) gaps. These edge lines guide circulat- ing traffic around the roundabout and serve as an entrance line that marks the boundary separating entering and circulating traffic (see Section 126.96.36.199). The MUTCD prohibits the use of edge line extensions across the exit lanes. 188.8.131.52 Lane Lines The marking of lane lines within the circulatory roadway of a roundabout is a topic that continues to receive debate within the United States. Lane lines within the circulatory roadway provide guidance to drivers when done properly, and their use is endorsed by many countries around the world. There is some concern regarding whether lane lines introduce challenges with trucks straddling lanes; further research on this topic is anticipated. The 2009 MUTCD introduced new guidance under Section 3C.02 that multi- lane roundabouts should have lane line markings within the circulatory roadway to channelize traffic to the appropriate exit lane. These circulatory roadway lane line markings and lane-use arrows (see Section 184.108.40.206) should be designed to work together with approach lane line markings (see Section 220.127.116.11) and approach lane-use arrows (see Section 18.104.22.168) to ensure that once drivers have chosen the appropriate entry lane on the approach, they do not have to change lanes within the roundabout to use their desired exit. Lane lines are typically described in the MUTCD as ânormalâ lines, meaning that they should be 4- to 6-in. (100- to 150-mm) wide. The MUTCD prohibits the use of continuous concentric lane lines within the circulatory roadway of roundabouts, unlike in continental Europe where the prac- tice has been prevalent. Instead, lane lines should be designed to guide drivers along the roundabout circulatory roadway and toward the appropriate exit with- out requiring a lane change. This manages much of the problems associated with the exitâcirculating conflict caused by lane changes to exit. There are several possibilities for the marking pattern of lane lines within the circulatory roadway of roundabouts. Chapter 3C of the MUTCD does not discuss lane line marking patterns. However, the MUTCD figures show circulatory road- way lane lines as solid lines in front of the splitter island and dotted lines across the entry lanes, as illustrated in Exhibit 7-9. As stated in the MUTCD, the function of solid lines is to discourage or prohibit crossing, and the function of a dotted line is to provide guidance (as with a lane line extension through an intersection). The dilemma with circulatory roadway lane line marking patterns stems from the following facts: â¢ From the perspective of circulating traffic, a continuous solid line would be best to discourage lane changing within the circulatory roadway. This would appropriately support the principle of design to allow a driver to choose the appropriate lane on the approach and not need to change lanes to get to the desired exit. â¢ From the perspective of traffic entering a roundabout in any lane but the rightmost entry lane, a solid lane line across the roundabout entrance on
Chapter 7/Application of Traffic Control Devices Page 7-15 Roundabouts: An Informational Guide the circulatory roadway would discourage drivers from crossing the lane line to enter the appropriate lane, so it is useful to have a dotted line across the approach. Some practitioners have raised concerns that if a solid line transitions to a dot- ted line at the approach as shown in the figures in Chapter 3C of the MUTCD and illustrated in Exhibit 7-9, circulating drivers might think that they are allowed to change lanes at the dotted line prior to exiting the roundabout. This unintended behavior could result in an increase in exit crashes. Exhibit 7-10 illustrates an alternative marking pattern that has been used by some agencies within the United States. This strategy uses a uniform line pattern throughout the circulatory roadway and exits. The rationale for this pattern is that it is believed to be less likely to concentrate lane changes at the vulnerable entryâexit conflict area, and it is a line marking pattern that has been successfully employed in other countries. Common dimensions used for this type of marking consist of 6-ft (1.8-m) line segments and 3-ft (0.9-m) gaps. The reader should be aware that the 2009 MUTCD has introduced more specific definitions for line types in Section 3A.06, and the dimensions for the pattern shown in Exhibit 7-10 are not included within the allowed line types. Exhibit 7-9 Circulatory Roadway Lane Line Pattern Using Solid and Dotted Lines Exhibit 7-10 Alternative Circulatory Roadway Lane Line Pattern Using a Uniform Dotted Line
Roundabouts: An Informational Guide Page 7-16 Chapter 7/Application of Traffic Control Devices 22.214.171.124 Lane-Use Arrows Lane-use arrows within the circulatory roadway are an important component of the comprehensive system of signing and marking at roundabouts. These arrows provide confirmation to drivers, giving them confidence that they have entered in the correct lane and can continue circulating within this lane to get to their desired exit. When used within the circulatory roadway of roundabouts, normal lane-use arrows should be used, without a fishhook design and without an oval symboliz- ing the central island. Lane-use arrows are typically placed in the area in front of the splitter island, where the circulatory roadway lane line begins (see the addi- tional example exhibits in Appendix A). Arrows placed at this location are often visible to drivers as they approach the circulatory roadway, providing confirma- tion of lane choice as drivers enter the roundabout. 126.96.36.199 Bicycle Markings The MUTCD prohibits the use of marked bicycle lanes within the circulatory roadway. As described in more detail in Section 6.8, bicycle lanes should be terminated upstream of the roundabout entrance. 7.3.3 MINI-ROUNDABOUT PAVEMENT MARKINGS At mini-roundabouts, some pavement marking treatments are different from those at other urban roundabouts. The following pavement marking treatments are recommended for mini-roundabouts: â¢ Lane-use arrows. Lane-use arrows should be provided in the circulatory roadway adjacent to each splitter island to indicate the direction of circu- lation. No signs can be placed in the fully mountable central island, although the roundabout circulation plaque should be installed under the yield sign to legally establish the circulation direction within the round- about, as described in Section 188.8.131.52. Lane-use arrows provide an addi- tional indication of the circulation direction â¢ Yellow edge lines. Yellow edge lines are sometimes used along the left side of the approach roadway and circulatory roadway to delineate the mountable central island and splitter islands. Alternatively, the entire mountable central island and splitter islands are sometimes painted yel- low to improve their visibility. The splitter island may instead be delin- eated only by two sets of double yellow lines, rather than being a raised island. Trade-offs with this approach are discussed in Section 6.6. â¢ White edge lines. As described in Section 184.108.40.206, wide dotted edge line extensions (entrance lines) should be placed across the entry lanes of mini-roundabouts. Section 6.6 includes some important information about entrance line placement at mini-roundabouts. In addition, a solid white edge line may be used along the splitter island; if splitter islands are delineated only by two sets of double yellow lines, then this white edge line is recommended. â¢ Yield lines. Yield lines may be used to indicate the point behind which vehicles are required to yield at the entrance to a mini-roundabout, as The MUTCD prohibits bike lane markings on the circulatory roadway.
Chapter 7/Application of Traffic Control Devices Page 7-17 Roundabouts: An Informational Guide described in Section 220.127.116.11. However, most mini-roundabouts are simple enough that entrance lines are sufficient for this purpose. â¢ Crosswalk markings. As described in Section 18.104.22.168, crosswalk markings should be installed at mini-roundabouts, as with other roundabouts where pedestrian sidewalks and ramps are provided. Exhibit 7-11 illustrates a sample mini-roundabout pavement marking plan. 7.4 SIGNING The overall concept for signing of roundabouts is similar to signing of general intersections. Proper regulatory control, advance warning, and directional guid- ance enhance and support driver expectations. Signs should be located where they have maximum visibility for road users but a minimal likelihood of even momentarily obscuring vulnerable users, including pedestrians, motorcyclists, and bicyclists. Signing needs are different for urban and rural applications and for different categories of roundabouts. Only signs unique to roundabouts are shown here graphically. The reader is encouraged to refer to the MUTCD for details on other signs. The MUTCD pro- vides options for enhancing sign conspicuity in Section 2A.15. Exhibit 7-11 Example Markings for a Mini-Roundabout
Roundabouts: An Informational Guide Page 7-18 Chapter 7/Application of Traffic Control Devices 7.4.1 REGULATORY SIGNS A number of regulatory signs are appropriate for roundabouts and are described below. 22.214.171.124 Yield Sign A yield sign (R1-2) is required on the right side of each entry into the round- about. A second yield sign on the left side of the approach (mounted on the split- ter island) provides additional visibility and is particularly recommended for approaches with more than one lane. 126.96.36.199 Roundabout Directional Arrow Signs The roundabout directional arrow signs (R6-4, R6-4a, and R6-4b), shown in Exhibit 7-12, are new signs included in the 2009 MUTCD. These signs are the preferred method of indicating the direction of travel within the circulatory road- way. The black-on-white chevron design provides a regulatory message, legally establishing the direction of circulation at roundabouts. These replace the black- on-yellow chevron warning signs used previously, which are intended for use on horizontal curves. These signs should be placed on the central island opposite the roundabout entrances to direct traffic counterclockwise around the central island. On multilane approaches, high-speed approaches, approaches with limited visibility, or in other circumstances where increased sign visibility is desirable, the larger R6-4a or R6-4b signs are appropriate. For even more visibil- ity, multiple roundabout directional arrow signs may be used. The MUTCD allows a reduced minimum mounting height of at least 4 ft for the roundabout directional arrow signs. Yield signs are required on all approaches. Roundabout directional arrow signs establish the direction of traffic flow within the roundabout. Exhibit 7-12 Roundabout Directional Arrow Signs (R6-4, R6-4a, and R6-4b) Exhibit 7-13 One-Way Sign (R6-1R) One-Way signs can be used in addition to or instead of the roundabout directional arrow sign to establish the direction of traffic flow within the roundabout. R6-4 R6-4a R6-4b 188.8.131.52 One-Way Sign One-Way signs (R6-1R) may be used instead of or in addition to the round- about directional arrow signs (see Section 184.108.40.206) in the central island opposite the entrances to direct traffic counterclockwise around the central island. These are required in some states where the circulatory roadway of the roundabout is legally defined as a one-way roadway (rather than being the interior of an intersection). The R6-1R sign shown in Exhibit 7-13 is recommended for use at roundabouts, not the R6-2 version of the one-way sign.
Chapter 7/Application of Traffic Control Devices Page 7-19 Roundabouts: An Informational Guide Roundabout Directional Arrow signs are preferred over One-Way signs for several reasons: â¢ The black-and-white chevron design of the Roundabout Directional Arrow signs is unique and can only be used at roundabouts. Therefore, consistent and uniform use of this sign will serve to remind road users when they are entering a roundabout. â¢ The use of One-Way signs at roundabouts could result in some road users incorrectly concluding that the cross street is a one-way street. One-Way signs may be especially confusing at an intersection where the cross street is actually a one-way street traveling from right to left from the perspec- tive of an approaching driver. In some states, the vehicle code or other statutes define a roundabout as a series of T-intersections. In these areas, One-Way signs may be necessary to legally establish the direction of travel within the circulatory roadway. These One-Way signs may be supplemented with roundabout directional arrow signs as unique signs that help identify roundabouts. The black-on-yellow One-Direction Large-Arrow warning sign should not be used at roundabouts. 220.127.116.11 Roundabout Circulation Plaque At mini-roundabouts, the Roundabout Directional Arrow signs or One-Way signs cannot be placed within the central island due to the island being fully mountable. In these situations, the MUTCD provides a Roundabout Circulation (R6-5P) plaque, as shown in Exhibit 7-14. This sign is placed below each yield sign on each approach to the roundabout to define the direction of circulation within the roundabout. This is a new sign that was created specifically for this purpose and included in the 2009 MUTCD. Exhibit 7-14 Roundabout Circulation Plaque (R6-5P) The Roundabout Circulation plaque may also be placed below the yield signs on approaches to roundabouts to supplement the Roundabout Directional Arrow signs or one-way signs. 18.104.22.168 Keep Right Sign Keep Right signs (R4-7 or text variations R4-7a and R4-7b) are commonly used at the nose of non-mountable splitter islands. For small splitter islands, a narrow Keep Right sign (R4-7c) or an object marker are sometimes used as a substitute. This may reduce sign clutter and improve the visibility of the yield sign and other signs on a roundabout approach. The use of internally illuminated bollards is dis- cussed in Section 7.4.4.
Roundabouts: An Informational Guide Page 7-20 Chapter 7/Application of Traffic Control Devices 22.214.171.124 Intersection Lane-Control Signs For roundabouts with multiple entry lanes, as for any intersections with multi- ple entry lanes, drivers benefit from a consistent system of signing and marking telling them which lanes to use for the various left, through, and right movements. This is particularly important if the lane configuration is not consistent with the default rules of the road: left turns allowed only from the leftmost lane, right turns allowed only from the rightmost lane, and through movements allowed from any lane. Intersection lane-control signs may be used on multilane roundabout approaches (R3-5 through R3-8) to complement the lane-use arrows and other pave- ment markings and provide a consistent message to the traveling public. Advance intersection lane-control signs (R3-8 series) are preferred at roundabouts, although there may be occasions where other lane-control signs may be appropriate. Intersection lane-control signs are not necessary on single-lane approaches or at a typical two-lane roundabout, where the leftmost entry lane is for left turns and through movements and the rightmost entry lane is for right turns and through movements. At more complex roundabouts, intersection lane-control signs are more important. Intersection lane-control signs should be used at round- about approaches with double left-turn or double right-turn lanes and at other multilane roundabouts where the signs used in conjunction with lane-use arrows will improve lane utilization by drivers. The MUTCD includes several options for arrow symbols on intersection lane- control signs, as shown in Exhibit 7-15 and Exhibit 7-16. The fishhook arrows and the circle symbolizing the central island shown in this exhibit have been proposed by some agencies to provide additional clarification to drivers that they must cir- culate around the central island when traveling along the circulatory roadway. Lane-control signs should be provided as far in advance of the intersection as practical to allow time for drivers to select the appropriate lane for their maneuver prior to entering the roundabout. Exhibit 7-20 illustrates an example placement Intersection lane-control signs can be beneficial at multilane roundabouts, especially those with double turn lanes. Exhibit 7-15 Intersection Lane-Control Signing Options for a Roundabout Approach with Double Left-Turn Lanes Exhibit 7-16 Intersection Lane-Control Sign Arrow Options for Roundabouts Match arrows with desired lane- use configuration Match arrows with desired lane- use configuration Optional for left-most lane Optional for left-most lane A - Standard arrows B - Fish-hook arrows OR OR OR
Chapter 7/Application of Traffic Control Devices Page 7-21 Roundabouts: An Informational Guide of the lane-control signs adjacent to the corresponding lane-use arrow markings. An optional second set of lane designation signing (not shown in Exhibit 7-20) may also be provided upstream of the pedestrian crossing, adjacent to the second set of lane- use arrow markings. The redundant lane-use signing may help to reinforce the lane- use messages to drivers, particularly for more complex lane configurations. Any additional signs should be balanced against the concern for creating sign clutter. The MUTCD does not specifically address the use of overhead lane-control signs at roundabouts. It does recommend overhead lane-control signs at signalized intersections with lane drops, multiple-lane turns, or other unexpected lane-use regulations. At roundabouts, overhead lane-use control signs, if used, are likely most effective upstream of a roundabout and not at or near the entry due to the need for driver attention to other users at crosswalks and the entry. 126.96.36.199 Other Regulatory Signs â¢ Yield Here to Pedestrians and Stop Here for Pedestrians signs. These R1-5 series signs, used in conjunction with yield lines or stop lines in advance of mid- block crosswalks, have been shown to reduce the potential for multiple- threat crashes. However, at roundabouts, the installation of a yield line or stop line could be confusing for motorists, and these signs can potentially add to sign clutter on roundabout approaches. Therefore, as stated in the MUTCD, these signs should not be used in advance of crosswalks that cross an approach to or departure from a roundabout. There may be some exceptions to this recommendation, for example, where the crosswalk is much further than usual from the edge of the circulatory roadway. â¢ No-Left-Turn and No-U-Turn signs. The MUTCD prohibits the use of the No- Left-Turn (R3-2) sign, the No-U-Turn (R3-4) sign, and the combination No-U-Turn/No-Left-Turn (R3-18) sign at roundabout entries as a means to prohibit drivers from turning left onto the circulatory roadway of a round- about in front of the central island. The roundabout directional arrow signs provide clear guidance to drivers upon entry as to the correct direction of travel to navigate the roundabout. Section 188.8.131.52 describes many other cues to drivers that they should not turn left onto the circulatory roadway. In addition, lane-use arrow pavement markings (see Section 184.108.40.206) and inter- section lane-control signs (see Section 220.127.116.11) include arrow-symbol options with fishhook arrows and an oval or circle symbolizing the central island, which are intended to further discourage drivers from inadvertently turn- ing left onto the circulatory roadway in front of the central island. 7.4.2 WARNING SIGNS A number of warning signs are appropriate for roundabouts and are described below. The amount of warning a motorist needs is related to the intersection setting and the vehicular speeds on approach roadways. The specific placement of warning signs is governed by the applicable sections of the MUTCD. 18.104.22.168 Circular Intersection Sign A Circular Intersection sign (W2-6), shown in Exhibit 7-17, should be installed on each approach in advance of the roundabout, particularly if the roundabout is not clearly visible on the approach. The purpose of this sign is to convey to road
Roundabouts: An Informational Guide Page 7-22 Chapter 7/Application of Traffic Control Devices users that they are approaching an intersection with the form of a roundabout. This sign, introduced in the 2003 edition of the MUTCD, has many advantages over advance warning signs that have been used at roundabouts in the past: â¢ It includes an easily recognizable symbol that is similar to the symbols used for roundabouts in other countries. â¢ It gives advance notice of the proper direction of circulation within the roundabout. â¢ It can be used universally for roundabouts with any number of legs. This sign is sometimes supplemented with an educational plaque with the legend âROUNDABOUTâ (W16-17P) or with an advance street name plaque (W16-8 or W16-8a). Advisory speed plaques have been used in the past as a supplement to the Circular Intersection sign but are no longer recommended for roundabouts in the MUTCD. In practice it is difficult to define an appropriate advisory speed: Should it be related to the slowest speed for through traffic (V2), the slowest speed of all movements (typically V4), or another speed (such as zero for potentially coming to a stop at the yield sign)? In addition, advisory speed plaques are usually only used for turns and curves, not intersections. 22.214.171.124 Pedestrian Crossing Sign Pedestrian Crossing signs (W11-2) may be used at pedestrian crossings at both entries and exits of roundabouts, supplemented with a diagonal downward pointing arrow plaque (W16-7P) showing the location of the crossing. Pedestrian Crossing signs should be used at all pedestrian crossings at multilane entries, multilane exits, and right-turn bypass lanes. Where installed, Pedestrian Crossing signs should be located in such a way to not obstruct the view of the yield sign. 126.96.36.199 Object Markers Object markers may be used at the nose of all non-mountable splitter islands in addition to or in lieu of Keep Right signs. Object markers are smaller and can be mounted at a lower mounting height than Keep Right signs. Using object markers instead of Keep Right signs may reduce sign clutter and improve the visibility of the yield sign and other signs on a roundabout approach. Type 1 and Type 3 Object Markers are both appropriate for splitter islands. Type 3 Object Markers are only 12 in. wide and can be placed on narrow splitter islands. Exhibit 7-17 Circular Intersection Sign (W2-6)
Chapter 7/Application of Traffic Control Devices Page 7-23 Roundabouts: An Informational Guide 188.8.131.52 Other Warning Signs â¢ Yield Ahead sign. The Yield Ahead sign (W3-2) has been used previously at some roundabouts to provide advance notice to drivers of the yield sign at the roundabout entrance. It is still permissible to use this sign on a round- about approach. However, due to the large number of other signs on round- about approaches, it is recommended that this sign be used only in special circumstances. For example, at rural roundabouts where there are no pedes- trian facilities and therefore no pedestrian warning signs, this sign could be placed downstream of the Circular Intersection sign (see Section 184.108.40.206). As drivers become more familiar with roundabouts, there will be an increasing awareness that a yield sign is to be expected whenever they see the Circular Intersection sign, roundabout-specific guide signs, and many of the other signs and markings that are unique to roundabouts, further reducing any need for Yield Ahead signs at roundabouts. â¢ Advance Pedestrian Crossing sign. In most cases where crosswalks are marked and Pedestrian Crossing signs (W11-2) are used at a crosswalk, designers also include a Pedestrian Crossing sign in advance of the cross- walk. However, on the approach and departure of roundabouts, using these advance signs would result in additional signs in an area where many other important signs need to be installed. Therefore, in most cases, advance Pedestrian Crossing signs are not recommended at roundabouts. Pedestrian Crossing signs at the crosswalk itself are more critical and may be used as described in Section 220.127.116.11. 18.104.22.168 Example Sign Layouts for Regulatory and Warning Signs Exhibit 7-18, Exhibit 7-19, and Exhibit 7-20 illustrate examples of regulatory and warning sign layouts for mini-roundabouts, single-lane roundabouts, and multilane roundabouts, respectively. Guide sign layouts are presented later in Section 7.4.3. 7.4.3 GUIDE SIGNS Guide signs are important in providing drivers with proper navigational information. This is especially true at roundabouts where out-of-direction travel may disorient unfamiliar drivers. A number of guide signs are appropriate for roundabouts and are described below. 22.214.171.124 Advance Signs Advance-destination guide signs should be used in all rural locations and in urban/suburban areas where appropriate. There are several types of guide signs that can be used in advance of roundabouts as described in the bullets below. These types include signs using just text and arrows as well as diagrammatic signs. On larger roads and in suburban or rural areas where space is available, diagrammatic signs are preferred because they reinforce the form and shape of the approaching intersection and make it clear to the driver how they are expected to navigate the intersection. Diagrammatic signs can be especially useful where the geometry of the roundabout is not typical, such as where more than four legs are present or where the legs are not at 90Â° angles to each other. Advance-destination guide signs are The Yield Ahead sign is only needed in special circumstances where the yield sign is not visible. The circular shape in a diagrammatic sign provides an important visual cue to all users of the roundabout.
Roundabouts: An Informational Guide Page 7-24 Chapter 7/Application of Traffic Control Devices Exhibit 7-18 Example of Regulatory and Warning Signs for Mini-Roundabouts Source: 2009 MUTCD (1) (Optional) (Optional) (Optional) (Optional)
Chapter 7/Application of Traffic Control Devices Page 7-25 Roundabouts: An Informational Guide Exhibit 7-19 Example of Regulatory and Warning Signs for Single- Lane Roundabouts Source: 2009 MUTCD (1) (Optional) (Optional) (Optional) (Optional) (Optional)
Roundabouts: An Informational Guide Page 7-26 Chapter 7/Application of Traffic Control Devices not necessary at local street roundabouts or in urban settings where the majority of users are likely to be familiar with the site. â¢ Text exit destination signs. Exit destination signs with only text and arrows (D1-2d and D1-3d, shown in Exhibit 7-21) may be used on approaches to roundabouts to indicate destinations for each exit from a roundabout. Curved stem arrows may be used to represent left-turn movements. â¢ Diagrammatic exit destination signs. Diagrammatic exit destination signs (D1-5, shown in Exhibit 7-22) may be used on approaches to roundabouts to indicate destinations for each exit from a roundabout. The arrows representing the legs of the roundabout can be designed to represent the approximate angle of the exit legs. Exhibit 7-20 Example of Regulatory and Warning Signs for a Two-Lane Roundabout with Consecutive Double Left Turns Source: 2009 MUTCD (1)
Chapter 7/Application of Traffic Control Devices Page 7-27 Roundabouts: An Informational Guide Exhibit 7-21 Exit Destination Signs with Text and Arrows Exhibit 7-22 Diagrammatic Exit Destination Sign Advance Street Name (D3-2) signs are sometimes installed in advance of roundabouts to provide road users with the name(s) of the next intersecting street (Exhibit 7-23). These are comparable to the Next Signal sign that is sometimes used in advance of signalized intersections. As an alternative to advance Street Name signs, a method to reduce sign clutter on roundabout approaches is to place advance street name plaques (W16-8 or W16-8a) above or below the Circular Intersection sign (W2-6), as described in Section 126.96.36.199. Overhead guide signs are another option for communicating destination and lane-use information on the roundabout approach. Overhead signing has been implemented at various locations throughout North America and may provide benefits, particularly on three-lane roundabouts. Overhead signing reduces the chances for truck or other large vehicles to obscure the view of a roadside mounted guide sign. However, a potential drawback is that driverâs attention is diverted upward toward the sign instead of on the roadway ahead. The roundabout envi- ronment, complexity of information being presented, and approach geometry
Roundabouts: An Informational Guide Page 7-28 Chapter 7/Application of Traffic Control Devices should be considered in the selection of roadside mounting versus overhead mounting of guide signs. 188.8.131.52 Exit and Departure Signs Exit guide signs (D1â1d and D1-1e) are recommended to designate the desti- nations of each exit from the roundabout (Exhibit 7-24). These signs are similar to conventional intersection direction signs or directional route marker assemblies except that a diagonal upward pointing arrow should be used. These signs can be placed either on the right-hand side of the roundabout exit or in the splitter island. Where feasible, placement within the splitter island is recommended to maximize visibility of the sign. For roundabouts involving the intersection of one or more numbered routes, route confirmation assemblies should be installed directly after the roundabout exit. These provide drivers with reassurance that they have selected the correct exit at the roundabout. These assemblies should be located no more than 100 ft (30 m) beyond the intersection in urban areas and 200 ft (60 m) beyond the intersection in rural areas. Where there are pedestrian crossings on the exit leg, these signs should be placed after the crosswalk. Exit guide signs reduce the potential for disorientation. Exhibit 7-24 Exit Guide Signs Exhibit 7-23 Advance Street Name Sign for Use at Roundabouts (D3-2) 184.108.40.206 Example Sign Layout for Guide Signs for Roundabouts Exhibit 7-25 illustrates examples of layouts for guide signs at roundabouts. Regulatory and warning sign examples are included in Section 220.127.116.11.
Chapter 7/Application of Traffic Control Devices Page 7-29 Roundabouts: An Informational Guide 7.4.4 SUPPLEMENTAL TREATMENTS Some agencies in the United States are experimenting with the use of flexible, internally illuminated bollards as a means to highlight the leading edge of a splitter island, particularly at mini-roundabouts where the central island is less visible. This is a common application in the United Kingdom, where the illuminated bollards are combined with a Keep Left sign, as shown in Exhibit 7-26. If combined with a Keep Right sign, the sign mounting height requirements of MUTCD Section 2A.18 apply. Exhibit 7-25 Example Sign Layout for Guide Signs at Roundabouts
Roundabouts: An Informational Guide Page 7-30 Chapter 7/Application of Traffic Control Devices Exhibit 7-27 Examples of Speed Reduction Treatments Exhibit 7-26 Internally Illuminated Bollard Cambridge, England, United Kingdom (a) Warning beacons (Leeds, Maryland) (b) Dynamic speed warning signs (Leeds, Maryland) (c) Rumble strips (Paola, Kansas) In cases where high approach speeds are expected [in excess of 50 mph (80 km/h)] and physical conditions suggest the need for treatments supplemental to the geometric design and traffic control devices described elsewhere in this document, the following measures may also be considered. (Examples of some of these treatments are given in Exhibit 7-27.) â¢ Warning beacons supplementing approach warning signs (see MUTCD Section 4L.03),
Chapter 7/Application of Traffic Control Devices Page 7-31 Roundabouts: An Informational Guide â¢ Rumble strips placed in advance of the roundabout, â¢ Speed-reduction markings placed transversely across travel lanes (see MUTCD Section 3B.22), and â¢ Vehicle-activated speed warning signs commonly triggered by speeds exceeding an acceptable threshold. These supplemental treatments can be considered for one or more approaches as conditions warrant. Note that roundabouts have been installed in high-speed environments without the use of any of the above treatments, so none of these should be viewed as essential. 7.5 SIGNALIZATION There are some situations where it can be beneficial to use traffic signals to supplement the yield control used at roundabout entries. Signalization at round- abouts can include metering signals for one or more entries or pedestrian signals at roundabout pedestrian crosswalks. This section discusses each of these tech- niques and also briefly discusses full signalization of the circulatory roadway. 7.5.1 METERING During peak periods, it is possible for the flow from one entry to dominate downstream entries to the point where insufficient gaps are available, causing exces- sive delays and queues at the downstream entry. In these cases, entrance metering can provide significant operational benefits during these peak periods. In some cases, metering may be a more economical solution than geometric improvements, especially if the traffic condition requiring metering is of a short duration. A basic metering system consists of two components: 1. A queue detector on the downstream entry that is experiencing excessive delays and queues. The queue detector should be placed relatively far back on the downstream entry to detect when there is a long queue that has formed due to the congestion. When a long queue is detected, the signal controller activates the metering signal. 2. A metering signal on the dominant approach, preferably set far enough back from the entry to minimize confusion with the yield sign. If the metering signal cannot be set back sufficiently, some countries (e.g., Australia) use a special changeable message sign that shows a yield sign but can be changed to read âStop on Red Signal.â An example of a simple metering system is shown in Exhibit 7-28. Another method of metering is the use, with appropriate timing, of a nearby upstream signalized intersection on the subject approach road. Unlike pure entry metering, such controls may stop vehicles from entering and leaving the round- about. Expected queue lengths on the roundabout exits between the metering signal and the circulatory roadway should be compared with the proposed queuing space. Metering can be effective in managing peak-period flow patterns.
Roundabouts: An Informational Guide Page 7-32 Chapter 7/Application of Traffic Control Devices Because of additional objectives and constraints, metering by upstream signals is generally not as effective as direct entrance metering. More than one entrance can be metered, and the analyst needs to identify operational states and evaluate each one separately to provide a weighted aggregate performance measure. Exhibit 7-29 gives examples of metering signals. Exhibit 7-28 Example Diagram Showing Metering Signal Operation in Clearwater, Florida Nearby intersection signals can also meter traffic, but are not as effective as direct entrance metering. Exhibit 7-29 Examples of Metering Signals (a) Approach metering signal (b) Approach metering signal Clearwater, Florida Melbourne, Victoria, Australia (c) Combination metering signal and changeable yield sign Brisbane, Queensland, Australia
Chapter 7/Application of Traffic Control Devices Page 7-33 Roundabouts: An Informational Guide 7.5.2 PEDESTRIAN SIGNALS AT ROUNDABOUTS There are several situations where it may be beneficial to signalize pedestrian crossings at roundabouts. At first it may seem contradictory to add pedestrian sig- nals at roundabouts since roundabouts are often used as a preferred alternative to signalized intersections. In addition, pedestrian signals add cost to the round- about that is already implicit in the signalized intersection alternative. However, it is important to note that signalized pedestrian crossings at roundabouts are fairly simple when compared to signalization at the large signalized intersections, and in some cases they may provide critical accessibility for all users. Signalized pedestrian crossings may be beneficial at roundabouts under at least the following conditions: â¢ High vehicular volumes. In areas with high vehicular volumes and moderate pedestrian activity, the number of available gaps for pedestrians to cross (assuming no vehicular yielding) may be insufficient for the volume of pedestrian traffic. In these cases, a pedestrian signal meeting the tradi- tional MUTCD pedestrian signal warrants may be beneficial. â¢ High pedestrian volumes. In areas with high pedestrian volumes, continuous or frequent pedestrian crossing activity can have a significant negative impact on motor vehicle capacity. In these situations, it may be appropri- ate to install pedestrian signals to meter the flow of pedestrians, allowing motorists to clear the crosswalks to enter and exit the roundabout. â¢ Accessibility at more complex crossing situations. At most roundabouts, most pedestrians have little difficulty crossing the roadway due to the pedes- trian features provided (as described in Chapter 6). However, as the number of lanes increase, the task of crossing becomes more complex for pedestrians and potentially impossible for pedestrians with vision impair- ments (see Chapter 2). Signalization of crosswalks is one possible treat- ment for improving the consistency of motorist yielding and the ability of all pedestrians to identify that it is safe to cross, particularly those with vision impairments. The current draft PROWAG includes a requirement to install accessible pedestrian signals at all crosswalks across any round- about approach with two or more lanes in one direction. The PROWAG requirement does not specify the type of signal except that it must be accessible, including a locator tone at the pushbutton and audible and vibrotactile indications of the pedestrian walk interval. 18.104.22.168 Crossing Operation and Alignment Considerations Perhaps the most important design consideration when considering a pedes- trian signal is the advantage gained by operating the crossing in two stages. A tra- ditional single-stage pedestrian signal can result in a significant amount of delay to vehicular traffic, potentially backing up exiting traffic into the roundabout. The provision of a two-stage pedestrian signal can significantly decrease delay to motorists while providing appropriate signalization for pedestrians, including those who are blind or have low vision. At a two-stage signalized pedestrian crossing, there are two separate pedestrian walk intervals, one for crossing the entry roadway and one for crossing the exit roadway.
Roundabouts: An Informational Guide Page 7-34 Chapter 7/Application of Traffic Control Devices Where two-stage pedestrian crossings are used, care must be taken in the design and placement of the pedestrian signals. If two pedestrian signals for dif- ferent walk intervals can be seen from the nearside, pedestrians might see the wrong signal and inadvertently cross at the inappropriate time. In addition, at most places where pedestrians push a button at a traffic signal, they receive a walk interval that takes them all the way across the street. At a two-stage crossing they only cross one half at a time; therefore, it is important to design the crossings and walkways in a way that reminds pedestrians that something different is occurring at these crossings. There are two methods to resolve these concerns. First, as described in Section 6.8, one option for the crosswalk alignment at roundabouts is to place each leg of the crosswalk approximately perpendicular to the outside curb of the circulatory roadway for both the entry lane(s) and the exit lane(s). This creates an angle point in the walkway on the splitter island. However, if the splitter island is too narrow, the angle point may be too subtle to prevent pedestrians from mistakenly observing the wrong signal (see Exhibit 7-30). In addi- tion, care is needed when locating accessible pedestrian signals within 10 ft (3 m) of each other on the splitter island to provide non-conflicting audible messages. A wider splitter island simplifies both display options and accessible messages. Exhibit 7-30 Pedestrian Signal Placement at Angled Crosswalk The second, more definitive method to resolve the concerns above is to offset the two crosswalks by providing a staggered walkway within the splitter island, as shown in Exhibit 7-31. The offset clearly indicates to pedestrians that there are two separate stages to the pedestrian signal, and it moves the pedestrian signal heads away from each other so that pedestrians will not be likely to observe the
Chapter 7/Application of Traffic Control Devices Page 7-35 Roundabouts: An Informational Guide wrong signal. If an offset is provided, it is beneficial to provide landscaping or a railing in the splitter island to guide pedestrians to the crosswalks. At mid-block crossing locations with raised medians, it is normally preferred that the cross- walks be offset to the right; this forces pedestrians to look toward the approaching traffic in the lanes they will be crossing next. This could also be done at a round- about pedestrian crossing. However, at a signalized pedestrian crosswalk at a roundabout, it can be beneficial to offset the crosswalks to the left, as shown in Exhibit 7-31, which moves the crosswalk for the exit lanes further away from the circulatory roadway. This provides more storage for stopped vehicles at the sig- nal, reducing the likelihood that traffic will back up into the circulatory roadway. 22.214.171.124 Traditional Red-Yellow-Green Signals Traditional red-yellow-green traffic signals can be used at roundabout cross- walks in a manner similar to a typical mid-block signalized pedestrian crossing. Exhibit 7-31 Pedestrian Signal Placement at Staggered Crosswalk (a) Overall perspective (Gatineau, Quebec, Canada) (b) View of exit signal (Gatineau, Quebec, Canada)
Roundabouts: An Informational Guide Page 7-36 Chapter 7/Application of Traffic Control Devices The signal would rest in green for motorists entering and exiting the roundabout, and the pedestrian signal head would display the steady upraised hand symboliz- ing âdonât walk.â When the signal is actuated by a pedestrian, the vehicle signal would change to yellow and then red, after which the pedestrian signal head dis- plays a walking person symbolizing the walk interval and then the flashing upraised hand symbolizing the pedestrian clearance interval. The key design consideration when considering traditional red-yellow-green signals is the potential for motorist confusion between the green display at the crosswalk and the yield sign at the entry. For this reason, if traditional red-yellow- green signals are used, they should be located far enough away from the round- about to minimize the likelihood of confusion. Other display types as discussed below may be preferable. 126.96.36.199 Pedestrian Hybrid Beacons (HAWK signals) The 2009 MUTCD includes a new traffic control device called the pedestrian hybrid beacon (also commonly referred to as a HAWK signal). This device has a unique signal display that is intended to provide a red device to stop traffic to allow pedestrians to cross, while creating less delay to vehicular traffic than a nor- mal red-yellow-green signal. The vehicular signal head is a three-section head with two red signal sections above a single yellow signal section. The display sequence provided in the MUTCD is shown in Exhibit 7-32. A normal pedestrian signal head is displayed to pedestrians at the crosswalk. When the beacon is actuated by a pedestrian, the vehicle signal goes from dark, to flashing yellow, steady yellow, then steady red during the pedestrian walk interval. The vehicle signal then dis- plays alternating flashing red during the pedestrian clearance interval. As indi- cated in state vehicle codes, a flashing red signal has the same meaning as a stop sign, so drivers would be allowed to proceed through the crosswalk after stopping if the pedestrian has cleared their portion of the crosswalk. Because drivers can proceed once a pedestrian clears the crosswalk, the pedestrian hybrid beacon is likely to result in less delay to motorists than a traditional red-yellow-green signal, even with both operating in two-stage operation. Section 4F.03 of the MUTCD provides additional provisions for the use of pedestrian hybrid beacons at roundabouts. In particular, the pedestrian signal heads may be dark (rather than displaying the upraised hand) while the pedestrian- actuated signal is also dark. This allows pedestrians to cross the roadway without Exhibit 7-32 Display Sequence for a Pedestrian Hybrid Beacon
Chapter 7/Application of Traffic Control Devices Page 7-37 Roundabouts: An Informational Guide activating the pedestrian signal if they so desire, which can further reduce delay to motor vehicles. 188.8.131.52 Other Displays There may be advantages to experimenting with other signal displays for pedestrian crossings at roundabouts to find the best solution. These types of sig- nal displays not currently allowed by the MUTCD are subject to MUTCD Section 1A.10 âInterpretations, Experimentations, Changes, and Interim Approvals.â 184.108.40.206 Warning Beacons at Pedestrian Crossings Yellow flashing warning beacons have been shown to increase the percentage of drivers who yield to pedestrians, which could potentially benefit pedestrians at roundabouts. Exhibit 7-33(a) gives one example of a pedestrian-activated warning beacon at a roundabout crosswalk. Current and future research will evaluate the potential for flashing beacons to improve accessibility for pedestrians who are blind or have low vision. For example, a beacon could be installed that starts flashing after being actuated by a pushbutton, and a speaker at the pushbutton transmits a verbal message that says âFlashing beacons are activated, but traffic may not stop.â In addition to traditional round yellow flashing beacons, rectangular rapid flashing beacons, as shown in Exhibit 7-33(b), can be used at pedestrian crossings at roundabouts. Although not yet included in the MUTCD, rectangular rapid flashing beacons have been given interim approval by FHWA as they have been shown to be more effective in increasing yielding rates compared to traditional round yellow beacons. Exhibit 7-33 Examples of Warning Beacons at Pedestrian Crossings (a) Traditional Yellow Round Beacon (b) Rectangular Rapid Flash Beacon Gatineau, Quebec, Canada St. Petersburg, Florida 7.5.3 SIGNAL MOUNTING LOCATION While the MUTCD allows for both post-mounted signals and overhead signals, overhead signals are used at most signalized intersections because they have been shown to provide safer operation than post-mounted signals, especially at large intersections with high approach speeds and high volumes of traffic. However, because roundabouts are typically slow-speed environments by design and there is
Roundabouts: An Informational Guide Page 7-38 Chapter 7/Application of Traffic Control Devices no need for left- or right-turn signal heads, post-mounted signals have often been deemed to be sufficient where signals are used at roundabouts. This is especially true at two-lane approaches to roundabouts where approaching drivers will have a post-mounted signal immediately adjacent to their lane. On approaches with three or more lanes, overhead signals may provide better visibility, especially to the middle lane(s). The use of post-mounted signals can significantly reduce the cost of installing pedestrian signals at roundabouts, and they may fit in better with the urban design goals where roundabouts are used in urban areas. Post-mounted signals may also be desirable because they keep driversâ focus near the roadway where they can easily see the queue of vehicles approaching the yield line; overhead signals may draw driversâ attention off of the roadway, possibly increasing the likelihood of rear-end crashes. 7.5.4 FULL SIGNALIZATION OF THE CIRCULATORY ROADWAY Full signalization that includes control of circulating traffic at junctions with major entrances is possible at large-diameter multilane traffic circles or rotaries that have adequate storage space on the circulatory roadway. In these cases, the roundabout operates as a ring of coordinated signalized intersections and thus has operational characteristics that can be quite different from those described in this document. A detailed discussion of full signalization is outside the scope of this document. 7.6 AT-GRADE RAIL CROSSINGS Locating any intersection near an at-grade railroad crossing is generally dis- couraged. However, this is sometimes unavoidable and roundabouts are occa- sionally used near railroadâhighway at-grade crossings. Rail transit, including stations, has also successfully been incorporated into the medians of approach roadways to a roundabout, with the tracks passing through the central island. In such situations, the roundabout either operates partially during train passage or is completely closed to allow the guided vehicles or trains to pass through. Where an at-grade rail crossing is provided at a roundabout, design consideration should include the provision of traffic control (such as crossing gates and flashing lights) at the grade crossing consistent with treatments at other highwayârail grade crossings. The treatment of at-grade rail crossings should primarily follow the recommendations of the MUTCD. Another relevant reference is the FHWA Railroad-Highway Grade Crossing Handbook (2). Where roundabouts include or are in close proximity to a highwayârail grade crossing, a key consideration is the accommodation of vehicle queues to avoid queuing across the tracks. The MUTCD requires an engineering study to be con- ducted for any roundabout near a highwayârail grade crossing to determine queuing could affect the rail crossing and to develop provisions to clear the high- way traffic from the highwayârail grade crossing prior to arrival of a train (1).
Chapter 7/Application of Traffic Control Devices Page 7-39 Roundabouts: An Informational Guide There are three common ways in which rails can interact with a roundabout: 1. Within the roadway median and through the center of the roundabout, 2. Diagonally through the center of the roundabout, or 3. Across one leg in close proximity to the roundabout. Under any of the scenarios, highway traffic must not be forced to stop on the tracks. Where railroad gates are used to stop traffic, the gate placement and sequencing of the gates should be given careful consideration to allow all exiting traffic to clear the tracks prior to the train arriving. A gated rail crossing through the center of a roundabout can be accommo- dated in two ways. 1. Provide gates across only the at-grade rail crossing or 2. Provide gates across the at-grade rail crossing and across all roundabout entries. Issues to consider when designing such a crossing include but are not limited to the following: â¢ Location of the crossing relative to the roundabout. â¢ Traffic patterns and availability of queue storage. â¢ The use of railroad gates versus highway signals. Railroad signals fail- safe in that a loss of power drops the gate. Highway signals fail in flash or ultimately go dark. â¢ Preemption sequence and timing, including queue clearance, train speed, and other factors. Three common scenarios occur in practice. The first and most likely is where rails run parallel to the highway and cross one leg of the intersection, discussed in Exhibit 7-34. A second scenario is where rails pass diagonally through the central island of the roundabout, discussed in Exhibit 7-35. A third scenario is where rails run down the median of a roadway and pass through the central island of the roundabout, discussed in Exhibit 7-36. Other countries have considerable experience with the application of round- abouts near or incorporating at-grade rail crossings. While not inclusive of all international experiences, two examples are as follows: â¢ The city of Melbourne in Victoria, Australia, has several roundabouts with tram crossings running along the median through the center of the roundabout. These are either signalized or left uncontrolled. â¢ France also has considerable experience with at-grade rail crossings near roundabouts (3). Caution is recommended when applying international at-grade rail crossing experience to the United States due to differing laws, regulations, standards, and user experience.
Roundabouts: An Informational Guide Page 7-40 Chapter 7/Application of Traffic Control Devices Exhibit 7-34 Rail Crossing One Leg of the Intersection (a) Gates at all Entries (b) Gates on Rail Approach Only â¢ Allows all exiting vehicles to clear roundabout prior to train arriving. â¢ Introduces increases in delay, particularly where the predominant movement is through traffic parallel to the rail. â¢ Preferred where the rail crossing is close to the roundabout and insufficient storage is available between the roundabout and rail. â¢ Reduces delays at roundabout by allowing Â¾ of the roundabout movements to continue to operate normally with train present. â¢ Requires careful review of separation to rail line and available storage capacity.
Chapter 7/Application of Traffic Control Devices Page 7-41 Roundabouts: An Informational Guide Exhibit 7-35 Rail Crossing through Center of Roundabout (a) Gates at all Entries (b) Gates on the Circulatory Roadway â¢ Maximizes safety by stopping all entering vehicles to prevent interaction with the rail. â¢ Introduces minor increases in delay, particularly where there are heavy right turns. â¢ Preferred at small-diameter roundabouts where queue storage on the circulatory roadway is limited. â¢ Minor benefits from a delay standpoint where there are heavy right turns that can be accommodated while the train is present. â¢ Most practical at larger diameter roundabouts where queue storage is available for through and left-turn vehicles.
Roundabouts: An Informational Guide Page 7-42 Chapter 7/Application of Traffic Control Devices 7.7 REFERENCES 1. Manual on Uniform Traffic Control Devices for Streets and Highways. FHWA, Washington, D.C., 2009. 2. Railroad-Highway Grade Crossing Handbook, 2nd ed. Publication No. FHWA-SA- 07-010. FHWA, Washington, D.C., 2007. 3. Safety at Level Crossings: Case of Proximity to a Roundabout. SÃ©tra (Service dâÃtudes Techniques des Routes et Autoroutes), Bagneux, France, 2007 (translation). Exhibit 7-36 Rail Running down Roadway Median Gates at all Entries Gates on the Circulatory Roadway â¢ Maximizes safety by stopping all entering vehicles to prevent interaction with the rail. â¢ Introduces additional delay. â¢ Consider use where: â Left-turn volume across tracks is low, â Large diameter present to store left-turn vehicles, â Multilane roundabout that allows through vehicles to bypass queues. â¢ Provides reduced delay â¢ Introduces simultaneous conflicts between rail, queued vehicles, and through traffic.