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6-1 6.1 Introduction The Median U-turn (MUT) intersection refers to any intersection replacing direct left-turns at an intersection with indirect left-turns using a U-turn movement downstream of the inter- section, typically within a wide median. The MUT intersection eliminates left-turns on one or both intersecting streets and thus reduces the number of traffic signal phases and conflict points at the main crossing intersection. This can result in improved intersection operations and safety. The MUT is also known as a Median U-turn Crossover, a boulevard turnaround, a Michigan Left, or Thru-Turn Intersection. Exhibit 6-1. illustrates an example of an MUT intersection with a signalized main intersection and signals at each U-turn. At an MUT intersection, vehicles on the major street that would typically turn left at a signal- ized intersection are directed through the main crossing intersection, and then make a U-turn movement at a downstream directional crossover (that is usually signalized) and proceed back to the main crossing intersection (in the opposite direction from which the motorist came). Such vehicles then turn right onto the minor street. Directional crossovers are one-way median openings facilitating U-turns. Exhibit 6-1 depicts these movements. Similarly, vehicles on the minor street that would typically turn left at a signalized inter- section with the major street will turn right onto the major street, make a U-turn movement at the same directional crossover downstream, and then proceed through the main crossing street. The signals at the main crossing intersection (that permit only through and right-turn movements from both streets) and the signals at the U-turn crossovers (that alternate between through traffic on the major street and U-turn movements) are typically coordinated to mini- mize delays to both through and turning traffic. The geometric design of an MUT intersection introduces some unique design elements not typically present at a conventional intersection. These elements include ⢠A wide median, often needed to facilitate the MUT movements. Typically, this median is uniform through the intersection and main crossing street, but there are design variations reducing the length of the wide median or locating the median on the minor street. ⢠A large-enough vehicle path at the U-turn crossover to accommodate trucks and allow for efficient movements through the U-turn by passenger vehicles. ⢠Design elements providing positive guidance and signage to reduce the chances of driver error and discourage prohibited turns. ⢠Signing, marking, and geometric design promoting safe and efficient movements that would otherwise be unexpected or not familiar to motorists. ⢠Corridor-wide access strategies and management considerations to properties along the median street to promote safe and efficient access to these properties. C H A P T E R 6 Median U-Turn (MUT) Intersections
6-2 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges Portions of the material in this chapter are derived from earlier work for FHWA (1), updated to reflect the knowledge gained in this research. 6.2 Multimodal Operations This section presents the multimodal operational characteristics of an MUT intersection, starting with motorized vehicles and then explaining how pedestrians and bicyclists are served. 6.2.1 Motorized Vehicles The MUT intersection provides traffic operational benefits, particularly for through move- ments on the major street, by reducing the number of intersection signal phases and shortening overall signal cycle lengths. Despite requiring motorists to drive an additional distance com- pared to left-turns at a conventional intersection, MUT intersection left-turns usually have equal or improved delay times compared to a conventional intersection. Exhibit 6-2 illustrates concurrent movements at an MUT intersection. Exhibit 6-3 shows the typical signal locations for an MUT intersection. The MUT intersection, like many alternative intersections, removes left-turn phasing, which results in fewer clearance intervals in the intersection cycle (in this case, a reduction from four to two). The time formerly allocated for the redirected movements and eliminated clearance intervals can be allocated to other movements, thus improving intersection efficiency. An important aspect of MUT operations is that right-turn movement volumes increase due to the redirection of left-turn movements. These right-turn movements conflict with pedestrians Exhibit 6-1. Example of an MUT intersection. Exhibit 6-2. Concurrent movements at the main MUT intersection.
Median U-Turn (MUT) Intersections 6-3 and bicyclists. It may be necessary or desirable to restrict right-turn-on-red (RTOR) movements to provide adequate operational or safety performance for all modes, recognizing that it may increase delay for turning motorists at some MUT intersections. 6.2.2 Pedestrians Pedestrians can cross at the main MUT intersection and potentially at each of the U-turn crossover locations. With vehicular left-turns (and left-turn lanes or pockets) removed from the main intersection, the lengths of crossings for pedestrians can often be reduced compared to a conventional intersection, therefore reducing exposure. Cycle lengths can be reduced due to more efficient signal phasing, reducing pedestrian wait times. The following sections discuss pedestrian considerations at MUTs further. 6.2.2.1 Main Intersection Crossing The locations of pedestrian crossings at the main MUT intersection are essentially the same as those at a conventional intersection. However, the way these crossings are operatedâ one-stage versus two-stageâcan have a significant impact on operations for both pedestrians and motor vehicles. Exhibit 6-4 compares a single-stage versus two-stage crossing at an MUT intersection. Exhibit 6-3. Typical signal locations at an MUT intersection. Exhibit 6-4. Single-stage vs. two-stage crossing at MUT.
6-4 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges All else being equal, single-stage crossings are preferred so pedestrians are not unduly delayed and need not wait in the median between traffic streams. Single-stage crossings are also more common and thus are more likely to meet pedestrian expectations. However, the width of the major street may result in pedestrian walk times longer than the green time required for vehicu- lar through movements on the minor street, which could otherwise be allocated for major street traffic. The pedestrian crossing would control the signal timing. In these cases, two-stage cross- ings can be used if the median cannot be narrowed at the main intersection. For a two-stage crossing to be viable, the median area must be wide enough to accommodate pedestrians, wheel- chairs, strollers, and/or bicycles. Despite the overall shorter cycle length that a two-stage crossing might allow (due to the shorter pedestrian clearance time required for crossing one direction of traffic at a time), the total pedestrian crossing time for an MUT intersection under a two- stage crossing is typically much greater than that of a single-stage crossing. Two-stage crossings also require pedestrians to wait within the intersection for the next crossing phase. The need to wait must be communicated to pedestrians with vision disabilities. Two-stage crossings require pedestrian detection and accessible pedestrian signals (APS) in the median. Several techniques are available to reduce a pedestrian crossing from two stages to one stage, as shown in Exhibit 6-5. 6.2.2.2 Potential Challenges With Right-turning Motor Vehicles Right-turning traffic volumes are higher at an MUT intersection than at the equivalent conventional intersection. This could create operational or safety challenges for both pedes- trians and motor vehicles. Exhibit 6-6 presents a summary of the techniques, advantages, and dis advantages of various treatments for the conflict between pedestrians and right-turning motor vehicles. 6.2.2.3 U-turn Crossover U-turn crossover intersections create additional opportunities for midblock pedestrian cross- ings using a traffic signal or pedestrian hybrid beacon (PHB). If signalized, crossover inter- sections typically have signals that only control major street traffic approaching the main crossing intersection. However, signals controlling both directions of the major street could be installed to facilitate pedestrian crossings, as shown in Exhibit 6-7. 6.2.3 Bicyclists On-street bicyclists using an MUT intersection have different experiences when traveling as a through movement, right-turn, or left-turn. The next sections discuss each of these. 6.2.3.1 Through Movements Bicyclists making through movements encounter relatively higher percentages of green time at MUT intersections compared to the same experience at conventional intersections. At MUT intersections, there is a higher proportion of right-turning vehicles compared to at a con- ventional intersection (given that traffic that would turn left at a conventional intersection is required initially to turn right at an MUT intersection), which results in more conflicts between the bicycle through and vehicle right-turn movements. 6.2.3.2 Right-Turn Movements The right-turn movements for bicyclists are similar to the right-turn movements at conven- tional intersections. If a through bicycle lane is provided between through and right-turn lanes for motor vehicles, bicyclists need to share the right-turn lane with motor vehicles when making a right-turn.
Technique Advantages Disadvantages Increase cycle length ⢠Allows pedestrian crossing to be completed within one cycle ⢠Increases time for minor street, possibly well beyond what is needed to serve motor vehicle traffic. ⢠May require considerably longer cycle length to cover full MUTCD requirements for pedestrian clearance time. Reduce median width at main intersection ⢠Reduces pedestrian clearance time ⢠May require alignment adjustments of the major street Reduce the number of lanes on the major street ⢠The redirection of movements may allow a reduction in lanes beyond just the left-turn lanes that are removed ⢠Reduction in lanes may increase delay for motorized vehicles and create queuing affecting locations upstream of the main intersection. Reduce the width of lanes on the major street ⢠Reduces pedestrian clearance time ⢠The effect on pedestrian clearance time is likely to be minor unless there are many lanes whose widths are being reduced ⢠Reducing lane width may be inappropriate in certain contexts Allow pedestrian movements to break coordination when called ⢠Allows pedestrian crossing to be completed within one cycle while keeping time for minor street only to what is needed for motor vehicles during cycles without pedestrian calls ⢠Transitions back into coordination may disrupt progression along the major street ⢠If pedestrian calls are frequent enough, coordination may never be maintained Provide pedestrian lead interval (with APS) ⢠Allows pedestrians to get a head start on crossing ⢠May increase the overall cycle length requirement Exhibit 6-5. Techniques to reduce MUT crossing from two stages to one stage. Technique Advantages Disadvantages Restrict right-turns- on-red (RTOR) ⢠Increases safety and reduces conflict potential for pedestrians and bicyclists ⢠May increase the green time needed for motor vehicles, resulting in longer overall cycle length and more delay for all modes Provide pedestrian lead interval (with APS) ⢠Allows pedestrians to get a head start on crossing ⢠Does not necessarily provide the same safety benefit for pedestrians crossing toward the turning vehicles Position stop line for through vehicles to be farther from the crosswalk than the stop line for right- turning vehicles ⢠Increases visibility between right-turning motorists and pedestrians ⢠May increase clearance time for through movements Exhibit 6-6. Techniques to manage conflict between pedestrians and right-turning vehicles at MUT.
6-6 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges 6.2.3.3 Left-Turn Movements Left-turning on-street bicyclists have three options for navigating an MUT intersection, as described below and illustrated in Exhibit 6-8 for left-turns on the major street and Exhibit 6-9 for left-turns on the minor street. These options are as follows: ⢠Bicyclists making a two-stage left-turn: Bicyclists approach the intersection on the right and follow the vehicular signal indications. When receiving the green indication, the bicyclists proceed across the intersection and stop in a two-stage bicycle turn box. When the cross street receives a green indication, bicyclists proceed along the cross street. Interim Approval IA-20, Interim Approval for Optional Use of Two-Stage Bicycle Turn Boxes (2) provides signing and pavement marking provisions for this option. ⢠Bicyclists following pedestrian crossing rules: Bicyclists approach the intersection and, instead of traveling through based on the vehicle indications, exit the street to the right and follow the pedestrian signal indications. ⢠Bicyclists following motor vehicle rules: Bicyclists approach the intersection on the right and follow the vehicular signal indications. When receiving the green indication or with an acceptable gap in cross-traffic (when turning on a red indication), the bicyclists enter the intersection, cross all lanes to the left side of the road, and proceed to the MUT crossover. Exhibit 6-7 Signalized midblock crossing. Exhibit 6-8. Left-turn options for bicyclists on the minor street at MUT intersection.
Median U-Turn (MUT) Intersections 6-7 When the green signal is received, the bicyclists complete the U-turn, crossing all lanes to the right side of the road, travel to the main intersection, and proceed through or turn right as necessary (just as a vehicle would). The bicyclist must cross all lanes of traffic between the main intersection and the MUT while vehicle traffic performs the same maneuver. This option is undesirable for bicyclists, but it is always legally permissible, even if other options are available. Of these options, the two-stage left-turn is the most natural for bicyclists and the most likely to be obeyed. The âvehicle rulesâ option exposes bicyclists to significant out-of-direction travel and potential vehicle conflicts, while the âpedestrian rulesâ option generates potential pedes- trian conflicts. However, the âpedestrian rulesâ option can be considered when upgrading sidewalks to multiuse paths, when an otherwise off-street bicycle path crosses the street at the intersection, or when the MUT is designed as a protected intersection (see Section 6.4 for example designs). 6.3 Safety and Comfort Characteristics This section discusses safety and comfort characteristics for pedestrians and bicyclists at MUT intersections. MUT intersections have been shown to result in vehicular safety benefits compared to conventional four-legged intersections. The safety benefits for vehicles are attrib- uted to eliminating left-turns at the main intersection and a simplification of driver decision- making (generally dealing with one direction of travel at a time). The MUT intersection offers potential safety benefits for pedestrians and bicyclists, but the effects are not well studied. The discussion of nonmotorized safety focuses on an assessment of conflict points as described below and of design flags. 6.3.1 Conflict Points Pedestrians crossing an MUT intersection encounter fewer distinct conflicting traffic streams than at a conventional intersection. At a conventional intersection, pedestrians cross the street with one-stage or two-stage crossing during the adjacent streetâs vehicle phase. At an MUT intersection, left-turns are removed from the main intersection and occur away from the inter- section, thus removing potential pedestrian exposure to left-turning vehicles. Exhibit 6-10 shows the intersection movements and pedestrian-vehicle conflict points at an MUT inter- section design. Exhibit 6-9. Left-turn options for bicyclists on the major street at MUT intersection.
6-8 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges Crosswalks can be marked across all intersection legs, as at a conventional intersection. Pedestrians at an MUT intersection cross the major street during the minor street through and right-turn signal phase, when the only legally concurrent movement conflicts possible are with minor street right-turning vehicles or major street right-turning vehicles making an RTOR. The number of conflict points is limited. However, the frequency of conflicts at each conflict point increases, because left-turn movements are consolidated into right-turn movements and the total number of vehicles crossing the crosswalk remains the same. The tradeoff is a reduction in concurrent conflicts but an increased volume for the remaining conflicting traffic flow. Further empirical research is needed to test the quantitative safety effect for pedestrians. Exhibit 6-11 shows the bicycle-vehicle conflict points at an MUT intersection with on-street bike lanes. For separated facilities, bicycle-vehicle conflicts match the pedestrian-vehicle con- flicts introduced above, given that pedestrian and bicycle crossings would be co-located. 6.3.2 PedestriansâKey Safety Challenges Given the reduction of vehicular movements at the main intersection through the elimination of left-turns, the MUT offers the opportunity for a simplified pedestrian experience. Despite this, some safety concerns that should be flagged in an ICE evaluation remain, including: ⢠The MUT results in an increased vehicular right-turning volume compared to a conventional intersection, because left-turns have to make a right-turn to get to the U-turn bay (minor street lefts) or make a right-turn after the U-turn maneuver (major street lefts). This could exacerbate the Motor Vehicle Right-Turns design flag (Section 4.4.1). An MUT intersection inherently avoids the Motor Vehicle Left-Turns design flag (Section 4.4.10). Exhibit 6-10. Pedestrian-vehicle conflict points at MUT intersection.
Median U-Turn (MUT) Intersections 6-9 ⢠The median at an MUT intersection can be wide, especially in retrofit applications where left-turn pockets are closed after the initial design. The mainline crossing can be relatively long, resulting in increased pedestrian exposure, and long flashing Donât Walk clearance intervals. A two-stage crossing with refuge in the (wide) median can break up these long crossings but may cause added pedestrian delay, as pedestrians have to potentially wait through two signal cycles. The median refuge helps to mitigate the multilane crossings design flag (Section 4.4.7). ⢠A supplemental pedestrian crossing can be provided at each U-turn location, given it is a signal-control location for the U-turns. The outbound vehicular travel lanes rarely are signalized but would need a control device or treatment if a crossing is provided to avoid forcing pedestrians to cross multiple uncontrolled high-speed vehicular travel lanes. Failure to signalize the outbound vehicular travel lanes would trigger the crossing yield- controlled or uncontrolled vehicle paths flag (Section 4.4.4). In consideration of these challenges and pedestrian conflict points, Exhibit 6-12 presents the design flags generally applicable to pedestrians at MUTs. Design flags and treatments whose discussion applies across alternative intersection types are in Chapter 5. Some design flags unlikely to be present at an MUT intersection include the following: ⢠Nonintuitive motor vehicle movements (Section 4.4.3): No motor vehicle movements are crossed over or otherwise approaching from an nonintuitive direction for people crossing at an MUT. Exhibit 6-11. Bicycle-vehicle conflict points at MUT intersection with on-street bike lanes.
6-10 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges ⢠Indirect paths (Section 4.4.5): An MUT intersection typically provides four crossings at the main intersection, meaning that circuitous pedestrian routes are unnecessary. ⢠Executing unusual movements (Section 4.4.6): The wayfinding, traversing, and crossing at MUTs is relatively straightforward, without unexpected directionality or nonintuitive turns. ⢠Long red times (Section 4.4.8): This design flag seems unlikely to be triggered at an MUT intersection, given that the two-phase signal via the reduction of left-turn is the essence of the MUT. These reductions allow for shorter cycle lengths and thus no long red time. ⢠Motor vehicle left-turns (Section 4.4.10): Left-turns are eliminated at an MUT intersection. 6.3.3 BicyclesâKey Safety Challenges For bicyclists using a shared-use path, the safety challenges discussed for pedestrians above apply. For bicycles traveling in on-street facilities, additional safety challenges include the following: ⢠Bicycle left-turns traveling in vehicular lanes face significant out-of-direction travel (to and from the U-turn), as well as safety risks in needing to perform a two-sided weaving maneuver across vehicle travel lanes with potentially high speeds, high volumes, or both. This safety concern is presented as the design flag Lane Change Across Motor Vehicle Travel Lane(s) (Section 4.4.16). Exhibit 6-12. Summary of design flags for pedestrians at MUT intersections. Design Flag Description Mode/Travel Path Motor Vehicle Right-Turns (Section 4.4.1) This flag would carry forward to the final design stage, based on right-turns. Because MUTs have relatively high volumes of right- turns, the geometry of the turning movement will be a critical factor in controlling speeds. Pedestrian, all crossings Crossing Yield- or Uncontrolled Vehicle Paths (Section 4.4.4) With the right-turns identified in the design flag above, pedestrians at the four crossings at the main intersection would cross a high volume of right-turning vehicles with a green signal indication. Pedestrian, all crossings Multilane Crossings (Section 4.4.7) The major street crossings at an MUT may be relatively long. A median refuge is common, but the single-direction travel lane configuration may remain a long crossing. Pedestrians, all crossings Undefined Crossing at Intersections (Section 4.4.9) This flag is not unique to MUTs but given the relatively high volume of right-turning vehicles conflicting with the pedestrian crossing, lack of clearly defined user space would be stressful for pedestrians. Pedestrians, all crossings
Median U-Turn (MUT) Intersections 6-11 ⢠Bicycle through movements face potential âright hookâ conflicts with vehicles turning right at the MUT intersection. With the vehicular right-turn movement increased, the frequency of this conflict (the Turning Motorist Crossing Bicycle Path design flag, Section 4.4.18) may also increase. ⢠If channelized lanes are provided on any approach, the design issues in Channelized Lanes (Section 4.4.17) apply. Safety concerns related to the design of the channelized lanes are described further in Chapter 5. Exhibit 6-13 presents the design flags applicable to bicycles at MUT intersections. Design flags and treatments whose discussion applies across alternative intersection types are presented in Chapter 5. Design Flag Description Mode/Travel Path Indirect Paths (Section 4.4.5) For bicyclists seeking to make a left-turn at the intersection, the U-turn as designed represents considerable out- of-direction travel (several hundred feet), which may exceed thresholds for yellow or red flags (see Section 4.4.6). Bicyclists making left- turns via U- turn maneuver at MUTs Multilane Crossings (Section 4.4.7) For bicyclists crossing with pedestrians or using a path, the major street crossings at an MUT may be relatively long. A median refuge is common, but the single- direction travel lane configuration may remain a long crossing. Bicyclists, all path crossings Undefined Crossing at Intersections (Section 4.4.9) The movements are not clearly demarcated for the common expectation for left- turning bicyclists to proceed straight through the signal and cross over traffic to make a U-turn. Bicyclists making left- turns via U- turn maneuver at MUTs Lane Change Across Motor Vehicle Travel Lane(s) (Section 4.4.16) Bicyclists making the U-turn maneuver must cross over one or several lanes of motor vehicle traffic on a tangent roadway section to position for the U-turn. Bicyclists making left- turns via U- turn maneuver at MUTs Turning Motorists Crossing Bicycle Path (Section 4.4.18) The expected relative high right-turn volumes at an MUT exacerbate potential conflicts between right- turning vehicles and through bicyclists. Through bicyclists (particularly on the minor street) Exhibit 6-13. Summary of design flags for bicyclists at MUT intersections.
6-12 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges 6.3.4 Other Safety Concerns Besides the preceding discussion of key pedestrian and bicycle safety concerns, there are other general benefits and concerns presented by MUT intersections. Design flags that are more universal and not unique to MUTs include the following: ⢠Intersection Driveways and Side Streets (Section 4.4.11); ⢠Sight Distance for Gap Acceptance Movements (Section 4.4.12); ⢠Grade Change (Section 4.4.13); and ⢠Off-tracking Trucks in Multilane Curves (4.4.20). Sometimes, these design flags may need to be resolved in subsequent stages of design. 6.4 MUT Intersection-Level Concepts Three design concepts are presented in this section to illustrate techniques for improving the pedestrian and bicyclist safety and operational performance of MUTs. These concepts are not suggested as designs to be replicated as is; rather, each concept illustrates design options within a context. The concepts mix design approaches and are intended to address the design flags presented in Sections 6.3.1 and 6.3.2. The designer should consider the factors discussed previ- ously in this guidebook when matching designs and treatments to the appropriate context. Following each concept is a discussion of the flags remaining with the designâthe flags not obviated by the design that would still need to be addressed. The designs include the following: ⢠MUT On-Street Bikeway Concept ⢠MUT Protected Intersection Concept ⢠MUT Shared-Use Path Concept Sections 6.3.1 and 6.3.2 present other key design flags subject to site-specific concerns and are not obviously presented or solved with the concepts presented below. 6.4.1 MUT On-Street Bikeway Concept This MUT concept (shown in Exhibit 6-14) is readily distinguished by its provision of on- street bike lanes. The concept would be appropriate for a low-speed and/or low-volume context Exhibit 6-14. MUT on-street bikeway concept.
Median U-Turn (MUT) Intersections 6-13 and provides an example for carrying existing bike lanes through an MUT; consult Sections 3.1 and 3.3 to consider intended bicycle design users and guidance for matching a bicycle facility to speed and volume conditions. 6.4.1.1 Benefits The design addresses these key elements regarding safety and comfort: ⢠Motor Vehicle Right-Turns design flag: Corner refuge islands tighten right-turn radii and extend physical protection for crossing pedestrians. This turn radius may ultimately need to be modified based on the intended design vehicle path, but the design would control speeds of right-turning vehicles. ⢠Indirect Paths design flag: For bicyclists, the design includes on-street bike lanes with two-stage turn boxes at the intersection to facilitate left-turns. This feature has the benefit of providing an intuitive left-turn movement for all bicyclists and mitigates the Indirect Paths design flag. (Note the two-stage turn box has interim approval with FHWAâitem IA-20). The two-stage turn boxes also prevent bicyclists from the need to cross over vehicle travel lanes at speed, eliminating the Lane Change Across Motor Vehicle Travel Lane(s) flag. For pedes- trians, the midblock (at the U-turn) crossings provide more potential for route directness by allowing pedestrians to cross upstream or downstream of the intersection. ⢠Multilane Crossings design flag: For pedestrians, the design includes a separate sidewalk system with exclusively signal-controlled crossings, including supplemental crossings at the U-turn locations. A refuge is provided for every pedestrian crossing to allow for two-stage crossings. This mitigates the Multilane Crossings design flag, though not completely (see Exhibit 6-13). ⢠Crossing Yield- or Uncontrolled Vehicle Paths design flag: All pedestrian crossings would be signal-controlled, eliminating the possible associated design flag. ⢠The design includes a narrowed median with loons (localized widening) to accommodate U-turns. ⢠The concept features a relatively compact main intersection footprintâthe smallest foot- print among MUT concepts shared in this guide. This brings potential right-of-way acquisi- tion or construction cost benefits, and residual benefits related to the pedestrian and bicyclist experiences (e.g., shorter crossings generally). 6.4.1.2 Challenges Emphasizing again that the design is not intended to be âready-made,â this concept leaves some design flags remaining, as presented in Exhibit 6-15. 6.4.2 MUT Protected Intersection Concept This MUT concept (shown in Exhibit 6-16) is distinguished by its implementation of a pro- tected intersection concept with separated bike lanes. The concept would be implemented in locations with either relatively high motor vehicle volumes or high speeds. The separated bike lane and intersection treatment provide a low-stress riding environment for people biking, including less confident bicyclists. This design is most associated with an urban or suburban environment; the intersection could either match back into existing separated bike lanes or pro- vide ramps for bicyclists to enter or exit the lane. The separated bike lane could be implemented as a shared-use path with pedestrian facilities, as shown in the next concept; the decision would rely upon expected pedestrian and bicyclist volumes (with a multiuse path supporting lower volumes). Consult Sections 3.1 and 3.3 to consider intended bicycle design users and guidance for matching a bicycle facility to speed and volume conditions.
6-14 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges Turning Motorists Crossing Bicycle Path (Section 4.4.18) Turning motorists cross the bike lane in this design with developing the major street right-turn lanes. On the major street, this crossover occurs at the supplemental U-turn intersection. Bicyclists, all approaches Riding between Travel Lanes, Lane Additions, or Lane Merges (Section 4.4.19) The right-turn lane development causes a âpocket bike laneâ for through cyclists on all intersection approaches, wherein they are forced to ride between motor vehicle traffic. Bicyclists, all approaches Flag Remaining Description Mode/Travel Path Motor Vehicle Right- Turns (Section 4.4.1) The right-turn volume will likely be relatively high for most approaches because at an MUT it is a consolidation of right-turn and left- turn movements. However, if the curb radii can keep speeds from exceeding 25 mph, the flag may be mitigated. Pedestrian, all crossings Multilane Crossings (Section 4.4.7) Although median refuges are included for crossing the major street, a crossing pedestrian would still cross three concurrent same- direction travel lanes crossing all streets, meriting a yellow flag. Pedestrians, all main intersection crossings Riding in Mixed Traffic (Section 4.4.14) The provision of the on-street bike lanes does require a bicyclist to ride alongside motor vehicle traffic entering, traversing, and exiting the intersection. Depending on prevailing speeds and volumes, this environment could deter some potential, less confident riders. Bicyclists, all approaches Bicycle Clearance Times (Section 4.4.15) Due to the wide median on the major street, bicyclists may face challenges completing a crossing of the major street before the clearance time is elapsed. Bicyclists, major street crossing Exhibit 6-15. Summary of design flags remaining with MUT on-street bikeway concept. 6.4.2.1 Benefits This design addresses these key elements regarding safety and comfort: ⢠Motor Vehicle Right-Turns design flag: The design includes the protected intersection con- cept with corner refuge islands that tighten turn radii and extent physical protection for crossing pedestrians. The turn radius would need to be refined based on the intended design vehicle path but would control right-turning vehicle speeds. Crossing pedestrians are pulled back to enhance their visibility.
Median U-Turn (MUT) Intersections 6-15 ⢠Indirect Paths design flag: For bicyclists, the design includes separated-street bike lanes with the ability to complete left-turns in two stages using the bike lane. This has the benefit of providing a more intuitive left-turn movement for all bicyclists and mitigates the Indirect Paths design flag. For pedestrians, the midblock (at the U-turn) crossings provide more potential for route directness by allowing pedestrians to cross the major street upstream or downstream of the intersection. ⢠Crossing Yield- or Uncontrolled Vehicle Paths design flag: All pedestrian crossings would be signal-controlled, providing safe crossing opportunities and eliminating the possible associated design flag. ⢠Undefined Crossing at Intersections design flag: Crossings for pedestrians and bicyclists are defined with this design; particularly for bicyclists, the separated bike lane gives positive guid- ance and wayfinding benefits throughout the intersection. ⢠Physical Separation for Bicyclists: This concept moves all riding away from mixed traffic with physical (horizontal and vertical) separation. Bicyclists would cross motor vehicle paths using marked crossings; consult Chapter 5 for guidance on these crossings. This design elimi- nates the following design flags: â Riding in Mixed Traffic; â Lane Change Across Motor Vehicle Travel Lane(s); â Turning Motorists Crossing Bicycle Path; and â Riding between Travel Lanes, Lane Additions, or Lane Merges. Where right-turning vehicles would cross the through bike movements, the crossings are recessed to promote bicyclist visibility. 6.4.2.2 Challenges The protected intersection concept leaves some design flags remaining, as presented in Exhibit 6-17. 6.4.3 MUT Shared-Use Path Concept This MUT concept (shown in Exhibit 6-18) is distinguished by its implementation of a shared-use path. The concept would be implemented in locations with either relatively high motor vehicle volumes or high speeds such that physical separation is advisable for bicycle facilities. The shared-use path would be appropriate where a relatively low mix of walking and biking would be expected; with high expected volumes, separate facilities would be recommended. The shared-use path treatment provides a low-stress riding environment for Exhibit 6-16. Protected intersection concept.
6-16 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges people biking, including less confident bicyclists. This design may be appropriate where an MUT intersection was tying into an existing roadway without bicycle facilities through bicycle ramps before and after the intersection. The path, which expands in width when it transitions to include bicycles, would be appropriate in the presence of heavy right-turns or trucks by allowing bicyclists to avoid these conflicts. Consult Sections 3.1 and 3.3 to consider intended bicycle design users and guidance for matching a bicycle facility to speed and volume condi- tions; consult Chapter 5 for information regarding the design requirements (e.g., width) of multiuse paths. A key concern with this concept is maintenance, especially in the snow. The presence and accumulation of snow can change the user experience considerably and must be accounted for when implementing a design with channelization and other similar roadway features. As with all intersections that feature channelizing islands with multimodal access, coordination is Exhibit 6-18. MUT shared-use path concept. Flag Remaining Description Mode/Travel Path Motor Vehicle Right- Turns (Section 4.4.1) The right-turn volume will likely be relatively high for most approaches because at an MUT it is a consolidation of right-turn and left- turn movements. However, if the curb radii can keep speeds from exceeding 25, the flag may be mitigated. Pedestrian, all crossings Multilane Crossings (Section 4.4.7) Although median refuges are included for crossing the major street, a crossing pedestrian would still cross three concurrent same- direction travel lanes crossing all streets, meriting a yellow flag. Pedestrians, all main intersection crossings Exhibit 6-17. Summary of design flags remaining with on-street bikeway concept.
Median U-Turn (MUT) Intersections 6-17 required between partner agencies in determining who maintains access through the islands during snow events. 6.4.3.1 Benefits This design addresses these key elements regarding safety and comfort: ⢠Motor Vehicle Right-Turns design flag: The design includes channelized right-turns with signal control. The right-turn vehicle conflict with pedestrians would be separated and con- trolled, eliminating this flag. ⢠Multilane Crossing design flag: The provision of channelized right-turn lanes on all approaches ensures that no single pedestrian crossing is over two lanes wide, eliminating the need for pedestrians to cross more than two lanes at one time. ⢠Indirect Paths design flag: For bicyclists, the design includes separated-street bike lanes with the ability to complete left-turns in two stages using the bike lane. This has the benefit of providing a more intuitive left-turn movement for all bicyclists and mitigates the Indirect Paths design flag. For pedestrians, the midblock (at the U-turn) crossings provide more potential for route directness by allowing pedestrians to cross the major street upstream or downstream of the intersection. ⢠Crossing Yield- or Uncontrolled Vehicle Paths design flag: All pedestrian crossings would be signal-controlled, providing safe crossing opportunities and eliminating the possible asso- ciated design flag. ⢠Undefined Crossing at Intersections design flag: Crossings for pedestrians and bicyclists are defined with this design; particularly for bicyclists, the separated bike lane gives positive guidance and wayfinding benefits throughout the intersection. ⢠Physical Separation for Bicyclists at conflict points: This concept moves riding away from mixed traffic at the intersection with ramps to transition bicyclists off-street. Bicyclists would cross motor vehicle paths using marked crossings; consult Chapter 5 for guidance on these crossings. This design eliminates the following design flags: â Riding in Mixed Traffic; â Lane Change Across Motor Vehicle Travel Lane(s); â Turning Motorists Crossing Bicycle Path design flags; and â Riding between Travel Lanes, Lane Additions, or Lane Merges. Where right-turning vehicles would cross the through bike movements, the crossings are recessed to promote bicyclist visibility. ⢠Bicyclist Traveling in Channelized Lane Adjacent to Motor Vehicles: Although the design provides channelized right-turn lanes, the shared-use path and the ramps leading to the path allow for right-turning cyclists to bypass this conflict point. ⢠Channelized turn lanes for motorist right-turns with loons to keep intersection as close to perpendicular as possible. The channelized turns also separate the conflict between right- turning vehicles and crossing pedestrians and provide visibility at these conflict points. These channelized crossings would be signalized. 6.4.3.2 Challenges Emphasizing again that the design is not intended to be âready-made,â this concept leaves several design flags as described in Exhibit 6-19. A separate challenge with this concept is the considerable footprint of the intersection and the right-of-way required. This can drive up costs and has indirect effects on the pedestrian and bicyclist experience (e.g., longer distances to cross).
6-18 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges 6.5 Detailed Design Techniques The design flag procedure and corresponding flags are outlined in Chapter 4, and generalized design techniques common to many intersection forms are discussed in Chapter 5. Discus- sion in this section is limited to unique characteristics or design aspects to assist in addressing potential flags in an MUT intersection. This includes: ⢠Right-turn movements; ⢠ADA and accessibility. 6.5.1 Right-Turn Movements Due to the redirection of left-turn movements at an MUT intersection, right-turn vehicular volumes tend to be higher at MUT intersections than at traditional intersections. These higher vehicular volumes can increase safety risks for both pedestrians and bicyclists. Single right-turn lanes are most likely to provide the best safety performance for pedestrians and bicyclists if designed under the guidance in Section 6.5.2 and Chapter 5. Channelized right-turns, particularly if signalized, may be desirable for pedestrians and cyclists in certain contexts when turning volumes are high. The separation of vehicle move- ments can remove the concurrent pedestrian-vehicle conflict with crossings between the through and right-turn movement. Any channelized turn lanes should be accessible per the guidance in NCHRP Report 834 (3) and discussed in Chapter 5. Some MUT intersections have used multiple lanes for right-turn movements, particularly on the minor street. Multiple right-turn lanes allow the rightmost lane to be dedicated to right- turning motorists and the leftmost lane to be dedicated to motorists making U-turn movements at the downstream crossover in the median. However, using multiple exclusive right-turn lanes creates challenges: ⢠They increase pedestrian crossing distance; ⢠They may introduce sight distance challenges between pedestrians and motorists; Flag Remaining Description Mode/Travel Path Crossing Yield- Controlled or Uncontrolled Vehicle Paths (Section 4.4.4) If not signalized or stop-controlled, the pedestrian and bicycle crossing of the channelized right-turn lane would result in a flag. Pedestrians and Bicyclists, channelized turn crossings Long Red Times (Section 4.4.8) If the channelized turn lanes are signalized, pedestrians likely could not cross the turn lane, the major street, and the second turn lane in one phase. Depending on the cycle length, this may trigger a flag. Pedestrians, all crossings at the main intersection Sight Distance for Gap Acceptance Movements (Section 4.4.12) Adequate sight distance should be provided for any channelized turn movement not signalized. Pedestrians and Bicyclists, channelized turn crossings Exhibit 6-19. Summary of design flags remaining with MUT shared-use path concept.
Median U-Turn (MUT) Intersections 6-19 ⢠They may provide more motorist capacity than is needed to serve expected demand; ⢠If bicyclists are served by on-street bike lanes, the two right-turn lanes create substantial conflicts at the point where the right-turn lanes are developed; and ⢠The right-turn lanes may require additional right-of-way. Some MUT intersections have used shared through-right lanes. These can introduce sub- stantial conflicts for on-street bicyclists if bicycle lanes are intended to be extended into and through the intersection. If shared through-right-turn lanes are used, separated bicycle facilities should be provided, and signal phasing should allow at least a leading interval for through bicyclists. This allows bicyclists to cross before the right-turning motorists can proceed. RTOR restrictions should be considered in these cases. Uncontrolled channelized right-turn lanes are seldom used at MUT intersections for various reasons: ⢠They induce undesirable weaving conflicts between the MUT main intersection and down- stream U-turn crossover that otherwise would not occur if vehicles had to stop or yield; ⢠They introduce longer crossings for pedestrians; ⢠They create accessibility challenges for pedestrians crossing the uncontrolled channelized turn lane; and ⢠They require additional street width and potentially additional right-of-way. 6.5.2 ADA and Accessibility Pedestrians with vision, mobility, or cognitive impairments should find crossing an MUT intersection similar to crossing a conventional intersection. The cues that pedestrians with vision impairments rely on to cross intersections, such as the sound of traffic parallel to their crossing, are similar in both intersection forms. The direct crossing path of an MUT intersection is rela- tively easy and convenient to use. All pedestrians will experience two-phase signal timing and a reduced number of conflicting traffic streams than at a conventional intersection. The basic principles for wayfinding and crossing tasks are presented in Chapter 2, and design techniques are presented in Chapter 5. 6.6 References 1. Reid, J., L. Sutherland, B. Ray, A. Daleiden, P. Jenior, and J. Knudsen. August 2014. Median U-turn Informa- tional Guide. Report FHWA-SA-14-069. FHWA, Washington, DC. 2. FHWA. Interim Approval for Optional Use of Two-Stage Bicycle Turn Boxes (IA-20). https://mutcd.fhwa.dot. gov/resources/interim_approval/ia20/index.htm. FHWA, Washington, DC. Accessed March 28, 2019. 3. Schroeder, B. J., L. Rodegerdts, P. Jenior, E. Myers, C. Cunningham, K. Salamati, S. Searcy, S. OâBrien, J. Barlow, and B. L. Bentzen. 2016. NCHRP Report 834: Crossing Solutions at Roundabouts and Channel- ized Turn Lanes for Pedestrians with Vision Disabilities: A Guidebook. Transportation Research Board of the National Academies, Washington, DC.
