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Appendix A Design Guide for Channelized Right-Turn Lanes
Chapter 1 Introduction Channelized right-turn lanes are turning roadways at intersections that provide for free-flow or nearly free-flow right-turn movements. Channelization can be provided in a variety of forms including painted pavement areas and curbed islands. Figure 1 illustrates an intersection with channelized right-turn lanes. While the figure shows channelized right-turn lanes in all quadrants of the intersection, channelized right-turn lanes may be appropriate in some quadrants, but not in others, depending on intersection geometry and traffic demands. Figure 1. Typical Intersection With Channelized Right-Turn Lanes The primary reasons for providing a channelized right-turn lane are (1): ⢠To increase vehicular capacity at intersections ⢠To reduce delay to drivers by allowing them to turn at higher speeds ⢠To reduce unnecessary stops ⢠To clearly define the appropriate path for right-turn maneuvers at skewed intersections or at intersections with high right-turn volumes ⢠To improve safety by separating the points at which crossing conflicts and right-turn merge conflicts occur ⢠To permit the use of large curb return radii to accommodate turning vehicles, including large trucks, without unnecessarily increasing the intersection pavement area and the pedestrian crossing distance Channelized right-turn roadway Channelizing island Channelized roadway width Radius A-1
Chapter 2 Consideration of User Types Many transportation agencies use channelized right-turn lanes to improve operations at intersections, although there may be advantages and disadvantages of channelized right-turn lanes for different roadway user types including motor vehicles, pedestrians, and bicyclists. Motor Vehicles The primary traffic operational reasons for providing channelized right-turn lanes are to increase vehicular capacity at an intersection, reduce delay to drivers by allowing them to turn at higher speeds, and reduce unnecessary stops. Channelized right-turn lanes appear to provide a net reduction in motor vehicle delay at intersections where they are installed. A yield-controlled channelized right-turn lane can reduce right-turn delay by 25 to 75 percent in comparison to intersection approaches with conventional right-turn lanes (2). This advantage in delay reduction would like be observed at channelized right-turn lanes with no traffic control on the right-turn roadway. It is generally accepted that channelized right-turn lanes improve safety for motor vehicles at intersections where they are used, but there have been concerns that channelized right-turn lanes may experience a higher proportion of rear-end crashes than other right-turn treatments. Recent research (2) assessed whether channelized right-turn lanes experience more crashes than intersection approaches with conventional right-turn lanes or shared through/right-turn lanes. Research results found that any difference in motor-vehicle safety performance between the three right-turn treatments was not conclusively established. At intersections with substantial truck volumes, channelized right-turn lanes permit the use of large curb return radii to accommodate large trucks, without unnecessarily increasing the intersection pavement area and the pedestrian crossing distance. Pedestrians A key concern with channelized right-turn lanes has been the extent of conflicts between vehicles and pedestrians that occur at the point where pedestrians cross the right-turn roadway. Conflicts with pedestrians may be likely at right-turn roadways because the driver's attention may be focused on the cross-street traffic or the placement of pedestrian crosswalks or pedestrian signals on channelized right-turn lanes may violate driver expectancy. For most pedestrians, crossing the channelized right-turn roadway may be a relatively easy task because such roadways are not very wide and because traffic is approaching from a single direction. However, pedestrians with vision impairment may have difficulty detecting approaching traffic because (a) right-turning vehicles are traveling a curved rather than a straight path; (b) there is not a systematic stopping and starting of traffic, as there would be at a conventional signal- or stop- A-2
controlled intersection; and (c) the traffic sounds from the major streets may mask the sound of traffic on the right-turn roadway. Despite these potential problems, channelized right-turn lanes also provide advantages for pedestrians. The provision of a channelized right-turn lane, while making it necessary for pedestrians to cross two roadways, often reduces the pedestrian crossing distance. Furthermore the channelizing island, particularly when bounded by raised curbs, serves as a refuge area for pedestrians, and improves safety by allowing pedestrians to cross the street in two stages. Bicyclists There may be an inherent risk to bicyclists at channelized right-turn lanes because motor vehicles entering the channelized right-turn roadway must weave across the path of bicycles traveling straight through the intersection, but no studies based on crash history are available to support this presumption. However, similar conflicts between through bicyclists and right-turn vehicles are present at conventional intersections as well. A-3
Chapter 3 Traffic Operational and Safety Considerations for Channelized Right-Turn Lanes Channelized right-turn lanes have a definite role in improving traffic operations and safety at intersections. Specific traffic operational and safety considerations related to channelized right- turn lanes are discussed below. Traffic Operational Considerations Channelized right-turn lanes can play a key role in reducing right-turn delay to vehicles. Channelized right-turn roadways may have no control or may be controlled by stop signs, yield signs, or signals. In comparison to intersection approaches with conventional right-turn lanes, channelized right-turn lanes with yield control can reduce right-turn delay to vehicles by 25 to 75 percent (2). This advantage in delay reduction has been observed for pedestrian crossing volumes up to 200 ped/h. Similar delay reductions would likely be observed for channelized right-turn lanes with no traffic control. Right-turn delay at signalized channelized right-turn lanes is generally higher than at yield- controlled channelized right-turn lanes, and is typically higher than or similar to the right-turn delay at conventional right-turn lanes at signalized intersections where right-turn-on-red (RTOR) operation is permitted. At signalized channelized right-turn lanes, it is common for traffic engineers to provide extra green time to the right-turn movement without increasing cycle length by overlapping the right turn with the cross street left turn. Figure 2 illustrates the concept of a right-turn overlap. A potential drawback of the right-turn overlap phasing is that U-turns cannot be permitted from the cross-street left-turn lane, as they may conflict with right-turning vehicles. The elimination of the U-turn can be a significant issue in states where U-turns are allowed at all intersections and in areas that have median access control and U-turns are the primary means of providing left-turn access to businesses. Thus, use of an overlap phase or other methods of providing additional green time to right-turning vehicles can substantially reduce the delay for a signalized channelized right-turn lane, but may result in other impacts to intersection operations. Where a signal is provided for pedestrians to cross a channelized right-turn lane on a cycle coordinated with the primary signal at the intersection, vehicle delay with the channelized right- turn lane is generally greater than vehicle delay for conventional right-turn lanes and for yield- controlled channelized right-turn lanes. The vehicle delay is independent of the pedestrian volume because the phase for crossing the channelized right-turn lane can be called every cycle in conjunction with the cross-street signal phase. A disadvantage of providing a pedestrian signal is that a pedestrian must wait for the pedestrian crossing phase to cross the channelized right-turn lane and then wait again for the pedestrian crossing phase of the primary intersection to cross the major or cross street. However, pedestrian signals are very important to pedestrians with vision impairment who cross at a channelized right-turn lane. Provision of a pedestrian-actuated signal should be considered. A-4
Figure 2. Right-Turn Overlap Traffic Safety Issues It is generally accepted that channelized right-turn lanes improve safety for motor vehicles, but there have been concerns about the safety of channelized right-turn lanes for pedestrians. Recent research (2) evaluated seven years of motor-vehicle and pedestrian crash and volume data from nearly 400 four-leg signalized intersection approaches in Toronto, Ontario, Canada. The Toronto data represented a unique resource because they included both vehicle turning- movement volumes and pedestrian crossing volumes by intersection approach, as well as crash data that could be classified by intersection approach and turning movement. The results of this research provide insights into the safety of motor vehicles and pedestrians at channelized right- turn lanes. Potts et al. (2) assessed whether channelized right-turn lanes experience more motor-vehicle crashes than other right-turn treatments, such as conventional right-turn lanes or shared through/right-turn lanes. The research results found that any difference between the three right- turn treatment types was not conclusively established. Concerns have been raised that channelized right-turn lanes may experience a higher proportion of rear-end crashes, particularly at the downstream end of a channelized right-turn lane as vehicles merge into cross-street traffic. The same research (2) compared rear-end crash experience at channelized right-turn lanes to that of conventional right-turn lanes and shared through/right-turn lanes and found no difference between the right-turn treatments that could be conclusively established. A key concern with channelized right-turn lanes has been pedestrian safety as pedestrians cross the right-turn roadway. Specifically, there have been concerns that the driver's attention A-5
may be focused on cross-street traffic and that the placement of pedestrian crosswalks or pedestrian signals on channelized right-turn lanes may violate driver expectancy. Research results (2) showed that channelized right-turn lane approaches and approaches with shared through/right-turn lanes have similar pedestrian crash frequencies, while conventional right-turn lane approaches have substantially more (70 to 80 percent) pedestrian crashes than either of the other two right-turn treatments, for average levels of pedestrian crossing volumes. This is likely because conventional right-turn lane approaches have longer pedestrian crossing distances. A further advantage of channelized right-turn lanes is that they have a refuge island for pedestrians, providing the opportunity for crossing the intersection in two stages. In addition, those pedestrians that cross two legs of an intersection with a channelized right-turn lane can complete their crossing without the need to cross the channelized right-turn lane. This eliminates a conflict with right-turning traffic that would occur with the other intersection types. Most highway agencies choose to provide channelized right-turn lanes for locations with lower pedestrian volumes than intersections in general. For example, at the intersection considered in a safety evaluation by Potts et al. (2), the average pedestrian crossing volume was 510 pedestrians per day for channelized right-turn lane approaches; 1,120 pedestrians per day for conventional right-turn lane approaches; and 2,077 pedestrians per day for shared through/right- turn lane approaches. While the findings reported by Potts et al. were normalized for pedestrian volume, the general highway agency practice of using channelized right-turn lanes at intersections with lower pedestrian volumes suggests that this is a reasonable approach. The findings (2) are based on a database with an 85th percentile pedestrian volume of 1,000 pedestrians per day. Therefore, caution should be exercised in using channelized right-turn lanes where pedestrian crossing volumes are high (i.e., greater than 1,000 ped/day). For most pedestrians, crossing the channelized right-turn roadway can be a relatively easy task because such roadways are not very wide and because traffic is approaching from a single direction. However, pedestrians with vision impairment may have difficulty detecting approaching traffic. Certain design considerations at channelized right-turn lanes may better facilitate the safety crossing of channelized right-turn lanes by pedestrians with vision impairment. These design considerations are discussed in Chapter 4. A-6
Chapter 4 Design Issues Related to Channelized Right-Turn Lanes The AASHTO Policy on Geometric Design of Highways and Streets (1), commonly known as the Green Book, provides guidance on the design of channelized right turns under the topic of turning roadways. The policy describes the design controls and criteria for turning roadways and recommends values for the design elements of the horizontal and vertical alignment and the cross section of turning roadways. Although the Green Book is the primary reference for roadway design, channelized right turns are also addressed in the AASHTO Guide for Planning, Design, and Operation of Pedestrian Facilities (2). Recent research (3) provides additional guidance on various design issues for channelized right turns. This section presents a discussion of the following geometric design issues as they relate to channelized right-turn lanes: ⢠Crosswalk location ⢠Special crosswalk signing and marking ⢠Island type ⢠Radius of turning roadway ⢠Angle of intersection with cross street ⢠Deceleration and acceleration lanes ⢠Traffic control ⢠Bicycle treatments Each of these issues is addressed below. Crosswalk Location There is not universal agreement on where the pedestrian crosswalk should be placed on a channelized right-turn roadway. A crosswalk could potentially be placed at any location along a channelized right-turn roadway. It is obviously desirable to place the crosswalk at whatever location would maximize safety, presumably the location where pedestrians who are crossing or about to cross the right-turn roadway are most visible to motorists and where motorists are most likely to yield to pedestrians, but there are no research findings to verify which of the potential crosswalk locations shown in the figure is most desirable. A majority of the sites (nearly 70 percent) evaluated by Potts et al. (3) had marked crosswalks located near the center of the channelized right-turn lane; only about 30 percent of crosswalks were located at the upstream or downstream end of the channelized right-turn lane. The highway agency survey conducted in NCHRP Project 3-72 (4) found that highway agencies prefer a crosswalk location near the center of a channelized right-turn lane; over 70 percent of A-7
highway agencies reported in the survey that their practice was to place crosswalks near the center of channelized right-turn lanes. There has been little research that evaluates how the crosswalk location affects crossings by pedestrians with vision impairment in terms of their ability to identify the appropriate time to cross or efficiently locate the crosswalk. While further research would be desirable to provide more complete recommendations based on field observations of pedestrians with vision impairment, orientation and mobility (O&M) specialists, who teach pedestrians with vision impairment how to better traverse intersections recommend that consistency of crosswalk location is important. Such a consistency would make it easier for O&M specialists to describe a typical channelized right-turn lane to pedestrians with vision impairment and teach procedures for crossing such lanes. There is no strong technical basis for recommending one crosswalk location over another, other than the need for consistency. However, consistency in locating crosswalks is important, especially to pedestrians with vision impairment, and current practice shows a clear preference for crosswalk locations near the center of a channelized right-turn lane. And, a crosswalk location at the center of the channelized right-turn lane moves vehicle-pedestrian conflicts away from both the diverge maneuver at the upstream end of the channelized right-turn lane and, especially, from the merge maneuver at the downstream end of the channelized right-turn lane. The only potential exception to a center crosswalk location for channelized right-turn lanes is that, where STOP sign or traffic signal control is provided on the channelized right-turn roadway, the crosswalk should be located beyond the stop line. In addition, at locations where the channelized right-turn lane intersects the cross street at nearly a right angle, the stop line and crosswalk may be better placed at the downstream end of the channelized right-turn lane, depending on the island size and location of sidewalk approaches. To summarize the recommended guidance for the placement of crosswalks at channelized right-turn lanes: ⢠Where the entry to the cross street at the downstream end of the channelized right-turn lane has yield control or no control, place the crosswalk near the center of the channelized right-turn lane. ⢠Where the channelized right-turn lane has STOP sign control or traffic signal control, place the crosswalk immediately downstream of the stop bar, where possible. Where the channelized right-turn roadway intersects with the cross street at nearly a right angle, the stop bar and crosswalk can be placed at the downstream end of the channelized right- turn roadway. A-8
Special Crosswalk Signing and Marking Marked crosswalks are the primary means of indicating the presence of a pedestrian crossing. However, drivers do not always yield the right-of-way to pedestrians simply because they are in a crosswalk. Other special crosswalk signing and marking treatments have been considered for use at pedestrian crossings on channelized right-turn roadways to enhance crossing safety for pedestrians, in general, and for pedestrians with vision impairment. These include: ⢠Use of a raised crosswalk to improve visibility of crosswalk for motorists and to better define crosswalk boundaries for pedestrians (Raised crosswalks are particularly helpful to pedestrians with vision impairment) ⢠Addition of reflective yellow-green signs both at the crosswalk and in advance of the crossing location (to supplement the high-visibility markings) ⢠Use of a real-time warning device to indicate to the motorist when a pedestrian is present in the area (may be activated via passive detection technologies such as microwave or infrared or via traditional methods such as push buttons) ⢠Use of dynamic message signs (for real-time or static warning messages to motorists) None of these traffic control approaches has been evaluated to prove its effectiveness for pedestrian crossings on channelized right-turn roadways. However, an informal comparison (3) of pedestrian and motorist behavior between observational field study sites with and without special crosswalk signing and marking (i.e., raised crosswalks with contrast pavement markings and additional signing) suggested that the additional signing and pedestrian crosswalk treatments may improve the motorist yield behavior and pedestrian use of the crosswalk. For example, the percentage of motorists yielding to pedestrians waiting at the curb was slightly better (47 percent vs. 40 percent) at sites with special crosswalk treatments. This suggests that additional emphasis on signing or other treatments may be needed to increase yielding for pedestrians waiting at the curb. Island Type A channelized right-turn lane consists of a right-turning roadway at an intersection, separated from the through travel lanes of both adjoining legs of the intersection by a channelizing island. At right-angle intersections, such channelizing islands are roughly triangular in shape, although the sides of the island may be curved, where appropriate, to match the alignment of the adjacent roadways. Islands serve three primary functions: (a) channelizationâ to control and direct traffic movement, usually turning; (b) divisionâto divide opposing or same direction traffic streams; and (c) refugeâto provide refuge for pedestrians. Most islands combine two or all of these functions. Islands for channelized right-turn lanes typically serve all three functions. The edges of channelizing islands may be defined by raised curbs or may consist of painted pavement or turf that is flush with the pavement. Most channelizing islands in urban areas are defined by raised curbs. Curbed islands are considered most favorable for pedestrians because A-9
curbs most clearly define the boundary between the traveled way, intended for vehicle use, and the island, intended for pedestrian refuge. Curbed islands can improve the safety for pedestrians by allowing them to cross the street in two stages. Orientation and mobility (O&M) specialists have a strong preference for raised islands with âcut-throughâ pedestrian paths because they provide better guidance and information about the location of the island for pedestrians with vision impairment than painted islands. Where curb ramps are provided, truncated dome detectable warnings are required at the base of the ramp, where it joins the street, to indicate the location of the edge of the street to pedestrians with vision impairment. Radius of Turning Roadway Design criteria for the radii of channelized right-turn roadways are a function of turning speeds, truck considerations, pedestrian crossing distances, and resulting island sizes. Such criteria are established in current design policy, but the needs of pedestrians and trucks are in conflict in setting such criteria. For example, large turning radii better accommodate large trucks negotiating through right-turn maneuvers, but may result in higher turning speeds on the right- turn roadway as pedestrians are crossing. On the other hand, channelized right turns provide one method for accommodating larger turning radii without widening the major-street pedestrian crossings and without increasing the intersection pavement area. Reduction of delay to turning vehicles is a key reason for providing a channelized right-turn lane, and recent research (3) found that increasing the radius of a channelized right-turn roadway reduces right-turn delay by approximately 10 to 20 percent for each 8-km/h (5-mi/h) increase in turning speed. Where right-turn volumes are high and pedestrian and bicycle volumes are relatively low, capacity considerations may dictate the use of larger radii, which enable higher- speed, higher-volume turns. However, small corner radii, which promote low-speed right turns, are appropriate where such turns regularly conflict with pedestrians, as higher speeds have been shown to result in a decrease in yielding to pedestrians by motorists. Angle of Intersection with Cross Street The alignment of a channelized right-turn lane and the angle between the channelized right- turn roadway and the cross street can be designed in two different ways (as illustrated in Figure 3): ⢠A flat-angle entry to the cross street ⢠A nearly-right-angle entry to the cross street The two designs shown in Figure 3 differ in the shape of the island that creates the channelized right-turn lane. The flat-angle entry design has an island that is typically shaped like an equilateral triangle (often with one curved side), while the nearly-right-angle design is typically shaped like an isosceles triangle. The flat-angle entry design is appropriate for use in channelized right-turn lanes with either yield control or no control, such locations with an acceleration lane, for vehicles at the entry to the cross street. The nearly-right-angle entry design can be used with STOP sign control or traffic signal control for vehicles at the entry to the cross street; yield A-10
control can also be used with this design where the angle of entry and sight distance along the cross street are appropriate. Deceleration and Acceleration Lanes Drivers making a right-turn maneuver at an intersection are usually required to reduce speed before turning. Similarly, drivers entering a roadway from a turning roadway accelerate until the desired speed is reached. Substantial deceleration or acceleration that takes place directly on the through traveled way may disrupt the flow of through traffic and increase the potential for Figure 3. Typical Channelized Right-Turn Lanes With Differing Entry Angles to the Cross Street [Adapted From (5)] Channelized Right-Turn Lane With Flat-Angle Entry to Cross Channelized Right-Turn Lane With Nearly Right-Angle Entry to Cross Street Sk et ch es b y M ic ha el K im el be rg A-11
conflicts with through vehicles. To minimize deceleration and acceleration in the through travel lanes, speed-change lanes, both for deceleration and for acceleration, may be provided by highway agencies. Figure 4 shows the typical use of deceleration and acceleration lanes in conjunction with channelized right-turns lanes. Figure 4. Channelized Right-Turn Lanes With Deceleration And Acceleration Lanes. There are no generally established criteria concerning where deceleration and acceleration lanes should be provided in conjunction with channelized right-turn lanes. The AASHTO Green Book (1) does not give definitive warrants for the use of speed-change lanes, but identifies several factors that should be considered when deciding whether to implement speed-change lanes: vehicle speeds, traffic volumes, percentage of trucks, capacity, type of highway, service provided, and the arrangement and frequency of intersections. Deceleration Lanes Right-turn deceleration lanes provide one or more of the following functions (6): ⢠A means of safe deceleration outside the high-speed through lanes for right-turning traffic. Deceleration lane Acceleration lane A-12
⢠A storage area for right-turning vehicles to assist in optimization of traffic signal phasing. ⢠A means of separating right-turning vehicles from other traffic at stop-controlled intersection approaches. The addition of a deceleration lane at the approach to a channelized right-turn lane provides an opportunity for motorists to safely slow down prior to reaching the crosswalk area at the turning roadway. Acceleration Lanes Acceleration lanes provide an opportunity for vehicles to complete the right-turn maneuver unimpeded and then accelerate parallel to the cross-street traffic prior to merging. The addition of an acceleration lane at the downstream end of a channelized right-turn lane can reduce the right-turn delay by 65 to 85 percent, depending on the conflicting through traffic volume, and may be considered where right-turn delay is a particular problem. Channelized right-turn lanes with acceleration lanes appear to be very difficult for pedestrians with vision impairment to cross. Therefore, the use of acceleration lanes at the downstream end of a channelized right-turn lane should generally be reserved for locations where no pedestrians or very few pedestrians are present. Typically, these would be locations without sidewalks or pedestrian crossings; at such locations, the reduction in vehicle delay resulting from addition of an acceleration lane becomes very desirable. Traffic Control Channelized right-turn lanes are used at signalized intersections (i.e., where traffic at the main junction between the intersecting streets is controlled by traffic signals) and at unsignalized intersections, typically two-way stop-controlled intersections (i.e., locations at which traffic on the minor road is controlled by stop signs, but there is no traffic control on the major road). Traffic on a channelized right-turn roadway generally proceeds independently of the signals or stop signs for through traffic on the intersecting streets. Laws concerning motorist obedience to traffic control devices generally apply to traffic control devices which motorists are facing, and motorists on a channelized right-turn roadway are not generally considered to be facing the signals or stop signs at the main intersection. Thus, any traffic control for motorists on a right- turn roadway must be provided by traffic control devices intended specifically for motorists on that roadway. The primary traffic control decision for a channelized right-turn roadway concerns the type of traffic control device to be provided at the downstream end of the right-turn roadway, where it enters the cross street. Traffic control alternatives include no control, yield control, stop control, and signal control. Recent research (3) found that signalized channelized right-turn lanes consistently experience more delay to right-turning vehicles than yield-controlled channelized right-turn lanes. Use of an overlap phase, as discussed in Chapter 3 and illustrated in Figure 2 of A-13
this Guide, can substantially reduce the delay for a signalized channelized right-turn lane, but may result in other impacts to intersection operations, such as the need to restrict U-turn maneuvers. Pedestrian signals can be used at pedestrian crossings on channelized right-turn roadways to enhance crossing safety for pedestrians, particularly for pedestrians with vision impairment. Where a signal is provided for pedestrians to cross a channelized right-turn lane, a pedestrian- actuated signal should be considered. Actuation reduces vehicle delay for other movements because the phase associated to crossing the channelized right-turn lane is called only when pedestrians or adequate vehicular demand is present. Bicycle Treatments There is a potential risk to bicyclists at channelized right-turn lanes because motor vehicles entering the channelized right-turn roadway must weave across the path of bicycles traveling straight through the intersection. However, the same type of conflict between through bicyclists and right-turning vehicles is present at all intersections, except at intersections where right turns are prohibited or at three-leg intersections where there is no leg to the right on a given approach. Highway agencies may want to consider using special pavement markings and signing, such as those illustrated in Figures 5 and 6, to highlight a preferred bicycle path through channelized right-turn lanes and to increase motorist awareness of bicyclists at channelized right-turn lanes. Hunter et al. conducted a before-after evaluation of the blue pavement markings and signing in Figures 5 and 6 and found that they resulted in an increase in motorists yielding to bicyclists and an increase in bicyclists following the marked path. Overall, the treatment appeared to result in a heightened awareness on the part of both bicyclists and motorists. A-14
Figure 5. Blue Pavement Marking Treatment at Channelized Right-Turn Lane (7) a. At entrance to channelized right-turn roadway b. At exit of channelized right-turn roadway A-15
Figure 6. Signs Used in Oregon Blue Bike Lane Program (7) A-16
Chapter 5 Typical Channelized Right-Turn Lane Designs This chapter presents diagrams of the following four typical channelized right-turn lane designs: ⢠Channelized right-turn lane with center crosswalk and yield control ⢠Channelized right-turn lane with center crosswalk, acceleration lane, and no control ⢠Channelized right-turn lane with center crosswalk and stop control ⢠Channelized right-turn lane with center crosswalk, signal control, and pedestrian signal Advantages and disadvantages of each design are presented below each diagram. A-17
Channelized Right-Turn Lane With Center Crosswalk and Yield Control Advantages ⢠Channelized right-turn lanes with yield control have been shown to reduce right-turn delay to vehicles by 25 to 75 percent in comparison to intersection approaches with conventional right-turn lanes. ⢠Channelized right-turn lanes generally result in reduced pedestrian crossing distances and exposure. ⢠Shorter signal phase times (of primary signal) are possible due to shorter pedestrian crossing distance. ⢠A consistent practice of placing the crosswalk near the center of the channelized right-turn lane would be beneficial to pedestrians with vision impairment, particularly if accompanied by a raised island with a cut-through path. ⢠The addition of a deceleration lane at the approach to a channelized right-turn lane provides an opportunity for motorists to safely slow down prior to reaching the crosswalk area at the turning roadway. Disadvantages ⢠The lack of a pedestrian signal can be especially challenging for pedestrians with vision impairment. ⢠Potential for queued vehicles to stack across the crosswalk. ⢠Channelized right-turn lanes generally have a greater intersection influence area in which driveways would need to be restricted. A-18
Channelized Right-Turn Lane With Center Crosswalk, Acceleration Lane, and No Control Advantages ⢠The addition of an acceleration lane can reduce the right-turn delay by 65 to 85 percent, depending on the conflicting traffic volume on the cross street. ⢠The addition of an acceleration lane may allow motorists to focus on the crosswalk area prior to having to address the task of merging with the cross-street traffic. ⢠Channelized right-turn lanes generally result in reduced pedestrian crossing distance and exposure. ⢠Shorter signal phase times (of primary signal) are possible due to shorter pedestrian crossing distances. ⢠A consistent practice of placing the crosswalk near the center of the channelized right-turn lane would be beneficial to pedestrians with vision impairment, particularly if accompanied by a raised island with a cut-through path. ⢠The addition of a deceleration lane at the approach to a channelized right-turn lane provides an opportunity for motorists to safely slow down prior to reaching the crosswalk area at the turning roadway. Disadvantages ⢠The addition of an acceleration lane to a channelized right-turn lane makes crossing very challenging for pedestrians with vision impairment. ⢠High-speed merging and weaving maneuvers may be challenging for bicyclists traveling on the cross street. ⢠Higher turning speeds may be a disadvantage for pedestrian crossings. ⢠The lack of a pedestrian signal can be especially challenging for pedestrians with vision impairment. ⢠Channelized right-turn lanes generally have a greater intersection influence area in which driveways would need to be restricted. A-19
Channelized Right-Turn Lane with Center Crosswalk and STOP Control Advantages ⢠Providing a STOP sign on the channelized right-turn lane may provide more crossing opportunities for pedestrians than yield control. The crosswalk should be placed immediately downstream of the stop line, where possible. ⢠Consideration should be given to designing the channelized right-turn roadway such that it intersects with the cross street at nearly a right angle. This provides the driver with less of a skew angle when searching for gaps in cross-street traffic. ⢠A consistent practice of placing the crosswalk near the center of the channelized right-turn lane would be beneficial to pedestrians with vision impairment, particularly if accompanied by a raised island with a cut-through path. However, where the channelized right-turn roadway intersects with the cross street at nearly a right angle, the stop line and crosswalk can be placed at the downstream end of the channelized right-turn roadway. ⢠The addition of a deceleration lane at the approach to a channelized right-turn lane provides an opportunity for motorists to safely slow down prior to reaching the crosswalk area at the turning roadway. Disadvantages ⢠STOP control results in increased delay for right-turning vehicles than yield control. ⢠There is a greater potential for longer right-turn queues with STOP control than with yield control. ⢠The lack of a pedestrian signal can be especially challenging for pedestrians with vision impairment. ⢠Channelized right-turn lanes generally have a greater intersection influence area in which driveways would need to be restricted. A-20
Channelized Right-Turn Lane With Center Crosswalk and Signal Control and Pedestrian Signal Advantages ⢠Providing a signal on the channelized right-turn lane may provide more crossing opportunities for pedestrians than STOP or yield control, particularly at locations with high right-turn volumes and pedestrian volumes. ⢠Provision of a pedestrian signal is especially beneficial pedestrians with vision impairment but may make crossing easier for all pedestrians. ⢠Ability to install dual right-turn lanes to increase capacity without impacting the pedestrian crossing distance for the intersection legs and the associated pedestrian crossing times in the traffic signal timing. ⢠Channelized right-turn lanes generally result in reduced pedestrian crossing distances and exposure. ⢠Shorter signal phase times (of primary signal) are possible due to shorter pedestrian crossing distance. ⢠A consistent practice of placing the crosswalk near the center of the channelized right-turn lane would be beneficial to pedestrians with vision impairment, particularly if accompanied by a raised island with a cut-through path. ⢠The addition of a deceleration lane at the approach to a channelized right-turn lane provides an opportunity for motorists to safely slow down prior to reaching the crosswalk area at the turning roadway. A-21
Disadvantages ⢠Signal control results in increased delay for right-turning vehicles than STOP or yield control, particularly when RTOR is not permitted. ⢠Some pedestrians will likely cross against the pedestrian signal. ⢠There is an additional cost of installing the traffic signal equipment for the channelized right-turn movement. ⢠Channelized right-turn lanes generally have a greater intersection influence area in which driveways would need to be restricted. A-22
References 1. American Association of State Highway and Transportation Officials, A Policy on Geometric Design of Highways and Streets, 2004. 2. American Association of State Highway and Transportation Officials, Guide for Planning, Design, and Operation of Pedestrian Facilities, 2004. 3. Potts, I. B., D. W. Harwood, K. M. Bauer, D. K. Gilmore, J. M. Hutton, D. J. Torbic, J. F. Ringert, A. Daleiden, and J. M. Barlow, âDesign Guidance for Channelized Right-Turn Lanes,â Final Report, NCHRP Project 3-89, Midwest Research Institute, July 2011. 4. Potts, I. B., D. W. Harwood, D. J. Torbic, D. K. S. A. Hennum, C. B. Tiesler, J. D. Zegeer, J. F. Ringert, D. L. Harkey, and J. M. Barlow, Synthesis on Channelized Right Turns on Urban and Suburban Arterials, Final Report, NCHRP Project 3-72, Midwest Research Institute, August 2006. 5. Zegeer, C. V., C. Seiderman, P. Lagerwey, M. Cynecki, M. Ronkin, and B. Schneider, Pedestrian Facilities Users Guide: Providing Safety and Mobility, Report No. FHWA- RD-01-102, Federal Highway Administration, March 2002. 6. Neuman, T. R., NCHRP Report 279: Intersection Channelization Design Guide, TRB, National Research Council, Washington, D.C., 1985. 7. Hunter, W. W., D. L. Harkey, J. R. Stewart, and M. L. Birk, Evaluation of the Blue Bike Lane Treatment Used in Bicycle/Motor Vehicle Conflict Areas in Portland, Oregon, Report No. FHWA-RD-00-150, Federal Highway Administration, August 2000. A-23
