Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges (2021)

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8-1 8.1 Introduction The displaced left-turn (DLT) intersection, also called a continuous flow intersection (CFI), is an at-grade intersection form that relocates left-turn movements at one or more approaches to the other side of the opposing traffic using a crossover upstream of the main intersection. This crossover allows vehicular left-turn movements on an approach and opposing vehicular through movements to proceed simultaneously, eliminating the need for a separate left-turn signal phase for the approach. The number of traffic signal phases and vehicular conflict points (locations where user paths cross) is reduced at a DLT intersection relative to a conventional intersection serving the same volume of traffic, which can result in improvements in vehicular operations and vehicular safety performance. The green time that would be allocated for the left-turn can be reallocated to serve other performance objectives. Exhibit 8-1 highlights the key characteristics of a DLT intersection. Pedestrian movements at DLT intersections often cross vehicle paths multiple times, while bicycle movements have typically been accommodated with shared use of travel lanes. Both multi- stage crossings and shared bicycle movements can pose safety and quality of service challenges; the needs of these road users need to be evaluated as part of the design process. Developing the geometric layout for an intersection configuration requires considering the relationship and interaction of safety, operations, and design. In addition, it requires under- standing the tradeoffs of the physical, environmental, and right-of-way constraints for the pro- posed DLT intersection when local conditions preclude ideal intersection layouts. The essential characteristics of a DLT intersection—the crossover and the reduction in signal phases—create tradeoffs for the designer to address in providing a safe and comfortable facility for bicyclists and pedestrians. This chapter conveys the geometric, operations, and safety con- siderations, as well as design flags specific to a DLT intersection design. In light of these charac- teristics, this chapter also provides techniques and treatments at a DLT intersection to help meet the design objectives presented earlier in this guide: maximizing safety, providing access and accessibility, managing delay and travel time, and providing reasonable comfort. 8.2 Multimodal Operations This section provides information about the unique multimodal operational character- istics of DLT intersections and how they affect elements such as traffic signal phasing and coordination. The discussion on operations relates these characteristics to the pedestrian and bicyclist experience to convey tradeoffs associated with designs and treatments. The guidance presented here builds on existing DLT intersection studies, which include operational perfor- mance studies, comparative performance studies, and simulation analysis (1). C H A P T E R 8 Displaced Left-Turn (DLT) Intersections

8-2 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges 8.2.1 Motor Vehicles A DLT can have up to four crossovers at a four-leg intersection. However, most of the DLT intersections in the United States include crossovers on one or two approaches (Exhibit 8-2). DLT intersections have also been implemented at three-leg intersections. The DLT intersection’s core trait—the reduction of signal phases by displacing the left-turn— is a design feature that can reduce operational delay for vehicles. The goal of this design is to reduce signal phases by providing as many concurrent movements as possible. The removal of phases can increase the green time for all movements and reduce the cycle length. In turn, the DLT intersection can achieve vehicular capacity higher than that of a conventional intersection with the same basic lane configuration, specifically when a heavy left-turn con- flicts with a heavy opposing through movement. This efficiency is amplified for motor vehicular capacity when all approaches include a DLT (i.e., when all four approaches, rather than two Exhibit 8-1. DLT intersection characteristics. Exhibit 8-2. Four-legged DLT intersection with displaced lefts on the major street.

Displaced Left-Turn (DLT) Intersections 8-3 approaches, use the displaced left-turns). This provides the opportunity to reduce four sig- nal phases (both protected left-turn pairs and both through movements) to two (both pairs of through and left-turn movements together). To design a DLT intersection that is safe and comfortable for bicyclists and pedestrians, this vehicular efficiency must be weighed against the needs of these users. 8.2.1.1 Traffic Signal Phasing The traffic signal phasing of a DLT intersection affects how pedestrians and bicyclists experi- ence the intersection. These characteristics can change in the development of the design and thus can be influenced early in concept development. Key features of signal operations as they pertain to pedestrians and bicyclists are as follows: • If right-turn bypass lanes are provided, pedestrian crossings across the bypass lanes may or may not be controlled by a signal. This can heavily influence the safety and comfort of those using the crossing. The design approach is discussed more in the next section and Section 8.5.2. • Left-turning bicyclists may face the undesirable task of making the movement as motorists do, using the DLT and sharing space with motorists in a long-channelized left-turn lane. Alternatives include two-stage bicycle turn boxes or a separated facility with crossing treat- ments, as presented in Section 8.3.4. Depending on the treatment, sufficient time for bicyclists to clear the intersection safely is necessary. • Although motorists making the DLT do not conflict with oncoming vehicular traffic, the pedestrian crossings of the minor street do compete in time and, in some designs, in space, with this movement. The design approaches to address this conflict are discussed in Section 8.2.2. 8.2.1.2 Right-Turns Right-turns at DLT intersections can either be controlled at the main intersection or channel ized with a bypass lane. The decision to channelize a right-turn lane is made based on the assumed motor vehicle turning movement volumes and on the performance objectives of the design. A right-turn lane developed alongside an on-street bicycle lane represents a design flag (Riding between Travel Lanes, Lane Additions, or Lane Merges; Section 4.4.19), and the design should follow the guidance in Chapters 3 and 5. A channelized turn lane also represents a design flag, discussed in Sections 4.4.17 and 8.5.3. Exhibit 8-3 provides an example of a DLT intersection with both a right-turn lane addition and channelization implemented. Exhibit 8-3. DLT intersection with right-turn lane addition and channelization, Austin Blvd and SR 741 in Miami Township, OH.

8-4 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges 8.2.2 Pedestrians Pedestrian crossings at DLT intersections differ from those at conventional intersections. The main reason for this difference is the position of left-turn lanes between opposing through lanes and right-turn lanes, which presents pedestrians with an unfamiliar crossing scenario (i.e., motor vehicle traffic approaching from a nonintuitive direction). Additionally, the geometry of the crossover may create a wide median that adds length to the mainline pedestrian crossing. As discussed in Section 8.2.1.1, a pedestrian competes for time with displaced left-turns, given the simplified signal phasing. There are two primary design approaches (locations) for providing pedestrian crossings: an outside crossing or an inside crossing. These crossing options affect the experience of pedestrians and operations for all users. 8.2.2.1 Outside Crossing This chapter will refer to the crossing concept in Exhibit 8-4 as the “outside” crossing, so named because the pedestrian crossing of the minor street (labeled b in Exhibit 8-4) crosses outside the concurrent DLT movement for the major street (i.e., the corner island between crossings a and b is physically outside of the northbound DLT). Although this example of an outside crossing is shown with channelized right-turn lanes on the minor street, they are not essential to the design. The key operational elements of this design are as follows: • Pedestrian crossings of the minor street (e.g., the b crossing) compete for time with the major- street DLT movement. In this example, a leading or lagging turn phase would be desirable to avoid concurrency with the adjacent left-turn movement. In some cases, the left-turn move- ment could be timed as a permissive left-turn movement with a flashing left arrow, but this would significantly increase the safety risk for pedestrians (refer to the Motor Vehicle Left- Exhibit 8-4. Partial DLT intersection with outside crossing option. The mainline pedestrian crossings are located outside of the displaced left-turns.

Displaced Left-Turn (DLT) Intersections 8-5 Turns design flag in Section 4.4.10). This minor street pedestrian crossing (crossing b) can operate at the same time as the major-street right-turn (westbound right), but this concurrent operation would not allow pedestrians to execute both crossings in a single protected phase. • The pedestrian crossing is typically designed to be completed in one stage (i.e., no intermediate refuge). • Pedestrian crossings of the major street (e.g., the c crossing) may require checking multiple traffic streams from alternate directions that include the DLT. Although the vehicle move- ments are controlled, this directional pattern is not common and therefore not intuitive (refer to the Nonintuitive Motor Vehicle Movements design flag in Section 4.4.3). Depending on the crossing length, the outside crossing design may result in a relatively long cycle length (greater than 120 seconds) with associated delay for pedestrians and bicyclists due to the desire to run the left-turn movements and pedestrian crossings sequentially rather than concurrently. With longer crossings, the potential is greater for a pedestrian with a lower walk- ing speed to not be able to cross the entire street in one cycle, thus introducing more delay. (See design flags Multilane Crossings, Section 4.4.7, and Long Red Times, Section 4.4.8). This option is most appropriate when crossing lengths (and thus pedestrian clearance times) are relatively short as a function of the intersection geometry. 8.2.2.2 Inside Crossing The second crossing option is the “inside crossing,” which provides refuge islands separating the DLT movements on the major street from the adjacent through movements on the major street, as shown in Exhibit 8-5. The inside crossing example presented here also includes a chan- nelized right-turn lane on the minor street, which may not be essential to the design. The key operational elements of this design are as follows: • The design separates the DLT crossing (labeled d in Exhibit 8-5) from the main crossing c. This allows for shorter crossings and can provide additional time for pedestrians to cross the DLT movement. Pedestrians crossing with major-street traffic may cross in a concurrent phase (but will need to cross the DLT separately). Exhibit 8-5. Partial DLT Intersection with Inside crossing option. The mainline pedestrian crossings are inside the displaced left-turns.

8-6 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges • The inside crossing achieves a shorter mainline crossing but requires more stages (compare c and d in Exhibit 8-5 to c in Exhibit 8-4). • The shorter crossings may benefit pedestrians by breaking up long crossings and provid- ing additional refuge, which may be of particular benefit to pedestrians with disabilities and slower-walking pedestrians. Operationally, a key question to consider is which pedestrian phases can run concurrently with vehicular phases. Crossing d (but not c) could run concurrently with the minor street through and left-turn phases. Crossings a and e could run with either phase. Because pedestrians could be coming from either direction (e.g., a to e or e to a), it is difficult to establish a phase sequence optimal for both crossing directions. If c and d are timed sequentially, one crossing direction could be provided optimal timing, but the delay for pedestrians would consistently be longer in the reverse direction. In a DLT intersection with four displaced left-turns, the additional displaced left-turns compli- cate the pedestrian phasing demands, but the general technique is the same. The inside crossing design includes shorter stages for crossing relative to the outside crossing, but it introduces more locations for potential delay. The inside crossing design further separates and simplifies each crossing by creating more shorter crossings. The design may pose challenges by requiring pedestrians to cross the intersec- tion through multiple signal cycles. The signal phasing may be adjusted to benefit certain cross- ing movements and directions, but not all. A possible permutation of the inside crossing for pedestrian operations is to separate the DLT even farther from the main intersection, as shown in Exhibit 8-6. This form essentially removes the crossing of the displaced left-turns from the main intersection, thus simplifying the phasing and reducing those potential sources of pedestrian delay at the main intersection. The corner land uses in this example are far from the main intersection. With the displaced left-turns at an extended distance, the achievable distance to access corner-adjacent land uses increases. 8.2.3 Bicycles Depending on vehicle volumes, speeds, and separation both approaching and through the DLT intersection, bicyclists will have varied options (and associated risks) for movements through the intersection. The likely desired approach for some left-turning bicyclists with on-street facilities would be to make the movement in two stages, shown in Exhibit 8-7 on a DLT intersection with the Exhibit 8-6. Relocating DLT movement farther from the main intersection.

Displaced Left-Turn (DLT) Intersections 8-7 inside crossing design. The left-turn for a bicyclist at a DLT intersection is complicated by the design location of the displaced left-turns (inside crossing versus outside crossing). This design provides a natural location for the two-stage left-turn queue box; the initial outside crossing design option in Exhibit 8-4 does not, as drawn, provide such a location to easily accommodate this movement. This example illustrates the need for the iterative, performance-based approach (discussed in Chapter 1) to adapt initial designs when such challenges are identified. The benefit of short cycle lengths especially applies to left-turning bicyclists completing a two-stage left-turn. If they arrive without enough time to clear the intersection, they would then wait for the opposing phase to finish and proceed through their two-stage left-turn over the next two phases. They would thus require 1.5 cycles (three phases) to traverse the intersection. An alternative approach for the left-turn is by providing a path or separated bike lane, as shown in Exhibit 8-8. The details of these facility types are presented in Chapter 5, and DLT intersection concepts showing these separated options are presented in Section 8.3.4. Here, the operational considerations of the crossing would be much the same as for pedestrians. A final option that is always available but typically chosen by only the most confident cyclists is to make a left-turn like a motor vehicle, making the crossover movement before the intersection and using the DLT. This approach may be unlikely in the peak hour with heavy vehicle volumes but could be used in off-peak periods, when motor vehicle volumes are lower, by highly confi- dent cyclists. In consideration of all such movements, the designer should establish signal timing that provides adequate time for bicyclists to clear the intersection before conflicting movements proceed (and that bicyclists are detectable at approaches). 8.3 Safety and Comfort Although crash data are often used to develop models or other tools that can help professionals make safety decisions about transportation facilities, crash data are often limited or unavailable for some facilities. With DLT intersections, the small number of existing intersections makes it difficult to make inferences or develop tools related to their safety performance or expected crash frequency or severity. One before-and-after study in Baton Rouge, Louisiana, showed a Exhibit 8-7. Two-stage left-turning bicycles with a two-stage turn queue box through a DLT intersection.

8-8 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges reduction in vehicle collisions and severity following the implementation of a DLT intersection (2) relative to comparable conventional intersections, while a 2018 study showed a total crash CMF of 0.88 (3). Other research on DLT safety has been limited. 8.3.1 Conflict Points In place of crash data, an often-applied strategy is to examine the number of conflict points at an intersection. Conflicts are correlated with collisions and are often used as a surrogate measure, particularly to compare different intersection forms. The nature of vehicle movements (acceler- ating or decelerating) and traffic control helps to focus attention on the conflict points at which pedestrian and bicyclist safety may be most affected by design. 8.3.1.1 Pedestrian Conflict Points at DLTs A pedestrian-vehicle conflict point exists anywhere a pedestrian walkway and a vehicular travel path cross, and a bicycle-vehicle conflict point exists anywhere a bicyclist path and a vehicle path cross. The pedestrian-vehicle conflict points for outside crossing and inside crossing DLT intersections are illustrated in Exhibits 8-9 and 8-10, respectively. The key conflict points denoted by an asterisk (those across the channelized right-turn lanes) may be uncontrolled crossing locations, with vehicles free-flowing and/or accelerat- ing, depending on the design of the intersection. Although this conflict is not exclusive to DLT inter sections, in some existing designs they are both uncontrolled and along accelerating vehicle paths, which represents a design flag (Crossing Yield- or Uncontrolled Vehicle Paths, Section 4.4.4). Section 8.5.3 discusses the design of channelized turn lanes at DLT intersections. The outside crossing design presents pedestrians with a crossing over three traffic streams of alternating direction, including the DLT movement. By contrast, the inside crossing presents more distinct crossing phases than the outside crossing for a diagonally crossing pedestrian. 8.3.1.2 Bicycle Conflict Points at DLT Intersections The bicycle-vehicle conflict points for a single approach of on-street bicycle movements and off-street bicycle movements through the intersection are presented in Exhibits 8-11 and 8-12, respectively. Exhibit 8-8. Left-turning bicycle movements with a separated facility through a DLT intersection.

Displaced Left-Turn (DLT) Intersections 8-9 Exhibit 8-9. Pedestrian-vehicle conflict point diagram for a DLT intersection with outside crossing design. Exhibit 8-10. Pedestrian-vehicle conflict point diagram for a DLT intersection with an inside crossing design.

8-10 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges For on-street bicyclists, a right-turn lane represents an uncontrolled conflict point. Depend- ing on the distance from the intersection at which bicycle and motor vehicle paths cross, it may be a decelerating vehicle movement. If channelization is provided, the conflict point is upstream of the intersection; otherwise, the conflict point is at the intersection (see Turning Motorists Crossing Bicycle Path, Section 4.4.18). Although this is not a unique challenge to DLT inter- sections, the common use of channelized right-turn lanes makes this a focus of their design. For bicyclists riding in a separated facility, the conflict points are more spatially concentrated, and the right-turn conflict point is recessed, or offset, relative to the design with an on-street bicycle lane. See Section 5.3.3 for details on offset crossings. Exhibit 8-11. Bicycle-vehicle conflict point diagram for a DLT intersection with an on-street bicycle facility. Exhibit 8-12. Bicycle-vehicle conflict point diagram for a DLT intersection with an off-street bicycle facility.

Displaced Left-Turn (DLT) Intersections 8-11 8.3.2 Pedestrians–Key Safety Challenges An analysis of the design characteristics of the DLT intersection reveals several key safety chal- lenges for pedestrians: • Providing a reasonable path and quality of service. A reasonable path through the inter- section–one that is relatively direct and has minimal travel delay—will keep pedestrians from circumventing the intended design. As discussed in Section 8.2.2, the inside crossing design approach may create a delay for pedestrians, given the number of crossing stages. Conversely, a long major-street crossing with an outside crossing design may extend cycle length and increase the delay in a different manner. Absent a reasonable path or with exces- sive delay, pedestrians will seek their own paths, sometimes placing themselves at risk. This idea is captured in the Indirect Path and Long Red Times design flags (Sections 4.4.5 and 4.4.8, respectively). • Right-turn vehicular movements. Whether or not the turn is channelized, the speed, visibility, and traffic control need to be managed to reduce the risk for pedestrians; this concern is repre- sented by the Motor Vehicle Right-Turns design flag (Section 4.4.1). • Pedestrian confusion. Pedestrians crossing the DLT may not know intuitively which way to look for conflicting vehicle traffic streams. Simplifying crossings (i.e., isolating conflicting movements to be crossed) reduces the burden for crossing pedestrians. This concern is repre- sented by the Nonintuitive Motor Vehicle Movements design flag (Section 4.4.3). Exhibit 8-13 presents the design flags applicable to pedestrians, along with where to find dis- cussion and applicable treatments. (Design flags and treatments whose discussion applies across alternative intersection types are in Chapters 4 and 5). 8.3.3 Bicycles–Key Safety Challenges Bicycle safety at DLT intersections is a function of the bicycle facility type and level of sepa- ration between bicycles and vehicular traffic. For bicyclists traveling on shared-use paths, the crossing concerns for pedestrians discussed above apply. The additional considerations of particular concern for bicycle safety at DLT intersections include the following: • As discussed in Section 8.2.3, there are three primary approaches for left-turning bicyclists through DLT intersections. The conflict points for all three such left-turning bicyclist move- ments are presented in Exhibits 8-11 and 8-12. Bicyclist safety at these conflict points depends on the vehicle speed/geometry and traffic control–factors controlled by the intersection design—as well as vehicle volume, which aids in the decision facility selection. • Short cycle lengths that still preserve adequate clearance time are essential for bicyclist com- fort and safety. The two-stage left-turn, or a left-turn with a separated path and crossings, is subject to delay given the need for subsequent phases. Preventing excessive delay for these cyclists promotes the use of the design as intended (Long Red Times, Section 4.4.8). • Through or left-turning bicyclists may struggle to clear the intersection during the allocated green time. This safety challenge depends on the street width—particularly the major street, which may be relatively wide in some configurations. This challenge is represented in the Bicycle Clearance Times design flag, discussed in Section 4.4.15. • The entrance to a channelized right-turn (merging) is a critical bicycle-vehicle conflict point. This conflict point is not unique to DLT intersections, and absent a channelized right-turn, drivers must still cross the path of through cyclists as they turn right at the intersection. Channelized right-turns are typically used at DLT intersections, as presented in Section 8.5.3. Thus, the motor vehicle right-turn manifests either as Channelized Lanes (Section 4.4.17) or as Turning Motorists Crossing Bicycle Path (Section 4.4.18).

8-12 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges • Traveling along a turn lane and sharing the lane with turning vehicles (displaced left or chan- nelized right-turn) can create difficulties. Although the left-turn is displaced, making a turn through the lane alongside a motor vehicle exposes a cyclist to risk. (Channelized Lanes, Section 4.4.17). Exhibit 8-14 presents the design flags applicable to bicyclists, along with reference to more detailed discussion and applicable treatments. Several of these conflict locations are addressed in the discussion of the respective design flag treatments beginning in Section 8.5. Others for which the design flag is not unique to DLT intersections are discussed in the relevant sections of Chapter 4. 8.3.4 Other Safety Concerns In addition to the preceding discussion of key pedestrian and bicyclist safety concerns, there are other general benefits and concerns presented by DLT intersections. Design flags relevant to bicyclists that are more universal and not unique to DLT intersections 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 (Section 4.4.20). Design Flag Description Mode/Travel Path Motor Vehicle Right-Turns (Section 4.4.1) Pedestrians, all main intersection crossings Nonintuitive Motor Vehicle Movements (Section 4.4.3) Pedestrians, all main intersection crossings Multilane Crossing (Section 4.4.7) DLTs typically include multiple through lane approaches and one or two displaced left-turns, bringing a major-street crossing to six or seven lanes, sometimes without refuge. Pedestrians, major-street crossings, and often minor street crossings Long Red Times (Section 4.4.8) Due to high volumes, DLTs typically have longer cycle lengths, even though they may have only two or three phases. Additionally, the presence of signalized channelized right-turns may result in a high number of stages required to cross the intersection. Pedestrians, all crossings Motor Vehicle Left- Turns (Section 4.4.10) As discussed in Section 8.2, pedestrians compete in time and space with the displaced left-turns. Signal phasing can reduce the effect on pedestrians, and geometric design can promote appropriately slow left-turn speeds. Pedestrians, all main intersection crossings This flag would carry forward to the final design stage. The right-turns at full or partial DLT intersections typically are channelized, so sight distance and control must be considered for pedestrian safety. Pedestrians crossing the DLT would not typically expect vehicles in the given direction—whether crossing is on the departing or receiving end of the displaced left-turn. Exhibit 8-13. Design flags applicable to pedestrians at DLT intersections.

Displaced Left-Turn (DLT) Intersections 8-13 8.4 DLT Intersection-Level Concepts Three design concepts have been developed to present options for improving pedestrian and bicyclist safety and operational performance at DLT intersections. These concepts are not sug- gested as designs to be replicated as is; rather, they illustrate the DLT intersection options possi- ble in various contexts. These concepts show displaced left-turns on the major street only (two of four approaches). Finally, these designs show various treatment options, especially for bicyclists. The designer must consider traffic volume and speed when matching designs and treatments to the appropriate context (discussion in Chapter 3, Section 3.3.2). Following each concept is a discussion of the design flags remaining with the design—the flags not obviated by the design that would still need to be addressed. The designs include the following: • DLT Bike Lane and Path Concept • DLT Protected Intersection Concept • DLT Median Walk Concept 8.4.1 DLT Bike Lane and Path Concept This partial DLT intersection concept (shown in Exhibit 8-15) is distinguished by its provi- sion of on-street bike lanes along with a shared-use path for right-turning bicyclists. The concept would be appropriate for a context of low motor vehicle speeds, low motor vehicle volumes, Design Flag Description Mode/Travel Path Long Red Times (Section 4.4.8) Because the preferred bicycle left-turn options include either a two-stage left-turn or off- street path with crossings, bicyclists’ travel time is sensitive to the entire cycle length and red times. The intersection design will optimally minimize excessive delay for bicyclists to discourage risk-taking behavior. Bicyclists, left-turn movements along approaches with DLT Bicycle Clearance Times (Section 4.4.15) The typically relatively large footprint of a DLT means that yellow and all-red phases designed around motor vehicle trajectories are probably insufficient for bicyclists to clear the intersection during the intended phase. Bicyclists, through movements Channelized Lanes (Section 4.4.17) The displaced left-turn is a channelized movement, and DLT intersections typically feature channelized right-turn movements. Riding alongside vehicles in either channelized movement creates stress. Bicyclists, left-turns and right-turns Turning Motorists Crossing Bicycle Path (Section 4.4.18) Developing a right-turn lane creates a motorist movement crossing over a bicycle path. Bicyclists, through movements Exhibit 8-14. Design flags applicable to bicycles at DLTs.

8-14 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges or both; the concept also provides an example for carrying existing bike lanes through a DLT intersection. 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. 8.4.1.1 Benefits This DLT intersection concept includes these benefits for bicyclists and pedestrians: • Crossing Yield-Controlled or Uncontrolled Vehicle Paths design flag: All pedestrian cross- ings are controlled in this concept. • Multilane Crossings design flag: An inside crossing pedestrian mainline crossing minimizes crossing distance and exposure to vehicular traffic. A tapered median also allows for a relatively narrow median at the mainline crossing, to shorten the crossing distance. • Riding in Mixed Traffic design flag: The provision of the on-street bike lane and the shared- use path allows users to select their desired riding position, providing for more highly confi- dent cyclists and those who would not use on-street facilities in this context. • Channelized Lanes design flag / Lane Change Across Motor Vehicle Travel Lanes design flag: For left-turning bicyclists, using a two-stage turn queue box removes the need to cross over vehicle travel paths and travel in a channelized left-turn lane on the major-street approach. Similarly, for right-turning bicyclists, the ramp to a shared-use path allows bypass of the channelized right-turn lane with a downstream ramp to return to an on-street bike lane. • Riding between Travel Lanes, Lane Additions, or Lane Merges design flag: The right-turn bypass lane includes (along the major street) a signalized reentry to control the bicycle-vehicle conflict for through bicyclists at this location. 8.4.1.2 Challenges Emphasizing again that the design is not intended to be “ready-made,” this concept leaves several design flags as described in Exhibit 8-16. In this analysis, the right-turning bicyclists are assumed to use the off-street path. 8.4.2 DLT Protected Intersection Concept This DLT intersection concept (shown in Exhibit 8-17) is characterized by the separated bike lane on all approaches and the shared crossings over channelized right-turn lanes. The separated Exhibit 8-15. DLT bike lane and path concept.

Displaced Left-Turn (DLT) Intersections 8-15 Flag Remaining Description Mode/Travel Path Motor Vehicle Right- Turns (Section 4.4.1) Channelized right-turn lanes can lead to high vehicle speeds. This flag can be eliminated by signalizing the movement or reducing speeds below 10 mph with raised crosswalks or other methods. Pedestrians, all movements Nonintuitive Motor Vehicle Movements (Section 4.4.3) For pedestrians crossing the major street, crossing over the DLT is unintuitive. Although the conflict point is controlled, it may be unexpected and presents accessibility challenges. Pedestrians, major- street crossings Crossing Yield- Controlled or Uncontrolled Vehicle Paths (Section 4.4.4) If not signalized or stop-controlled, the pedestrian crossing of the channelized right-turn lane would result in a flag. Pedestrians, all movements Indirect Paths (Section 4.4.5) The large channelizing island in the southeast quadrant results in the need for east- and westbound pedestrians to encounter significant out-of-direction travel to cross the channelized turn lane. Pedestrians, eastbound or westbound through the southern approach Multilane Crossings (Section 4.4.7) The minor street would require crossing over three lanes without refuge. Pedestrians, minor street crossings Long Red Times (Section 4.4.8) Pedestrians may require multiple phases or cycles to cross the intersection, given the separation of many crossings of conflicting phases. This is amplified if the channelized turn lanes are signalized. Because the design is a partial DLT, the signal phasing would likely include three phases, increasing the relative red share during which pedestrians must wait. Pedestrians, all crossings Motor Vehicle Left- Turns (Section 4.4.10) Pedestrians crossing the major street experience conflicts with the non- displaced left-turns from the minor street. Pedestrians, major- street crossings Sight Distance for Gap Acceptance Movements (Section 4.4.12) Adequate sight distance should be provided for any channelized turn movement not signalized. Pedestrians, all crossings Exhibit 8-16. Summary of design flags remaining with DLT bike lane and path concept. (continued on next page)

8-16 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges bike lane would be an appropriate design technique for locations with relatively high motor vehicle volumes, speeds, or both. The separated bike lane would provide a low-stress riding environment and encourage use by less confident bicyclists. Depending on the surround- ing facilities, the separated lane could match back into existing separated bike lanes or pro- vide ramps back to on-street facilities. Using a separated bike lane versus a shared-use path would depend on the number of pedestrians and bicyclists expected to use the facility; 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. Riding in Mixed Traffic (Section 4.4.14) Bicyclists using the on-street lanes would face increased safety risks if vehicle speeds or volumes along the road were elevated. Bicyclists, all movements except right-turns Bicycle Clearance Times (Section 4.4.15) Bicyclists using the on-street lanes may not clear the intersection with the yellow and all-red phases programmed to accommodate vehicle trajectories. Bicyclists, through movements Turning Motorists Crossing Bicycle Paths (4.4.18) Right-turning motor vehicles have to cross over the on-street bicycle lane to move into the right-turn pocket. Bicyclists, left and through movements Riding between Travel Lanes, Lane Additions, or Lane Merges (Section 4.4.19) For on-street through bicyclists, the right-turn lane add before the intersection results in bicyclists riding between the right and through lanes for an extended period. Bicyclists, through and left-turn movements Flag Remaining Description Mode/Travel Path Exhibit 8-16. (Continued). Exhibit 8-17. DLT protected intersection concept.

Displaced Left-Turn (DLT) Intersections 8-17 8.4.2.1 Benefits • Motor Vehicle Right-Turns design flag: The design includes the protected intersection con- cept with corner refuge islands that tighten turn radii and extend 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. • Crossing Yield- or Uncontrolled Vehicle Paths design flag: All pedestrian crossings would be signal-controlled, providing safe crossing opportunities and eliminating the possible associ- ated design flag. • 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. The separated bicycle lane removes the bicycle and motor vehicle crossover conflict points throughout the intersection, relocating conflict to a controlled crossing of right-turn channelized turn lanes. The channelized lane crossings would be bidirectional for pedestrians and bicyclists, with sufficient width and marking to provide for these movements. This design eliminates the following design flags: – Riding in Mixed Traffic – Turning Motorists Crossing Bicycle Path – Riding between Travel Lanes, Lane Additions, or Lane Merges • Outside Crossing Provision: The major-street pedestrian crossing would be made in a single stage, eliminating the extra delay that could be incurred waiting between two-stage crossings. 8.4.2.2 Challenges The protected intersection concept leaves some design flags remaining, as presented in Exhibit 8-18. 8.4.3 DLT Pedestrian Walkway Between Vehicle Lefts and Throughs Concept This DLT concept (presented in Exhibit 8-19) is distinguishable by the provision of the walk- ing path between the displaced left-turn and through lanes, as well as the absence of bicycle facilities along the major street. Based on the bicycle facilities, this concept would be expected to be implemented where a bicycle route of importance suitable for on-street facilities (the minor street) crosses a major arterial route that is not a critical piece of a planned bike network. Con- sult Sections 3.1 and 3.3 to consider intended bicycle design users and guidance for matching a bicycle facility to speed and volume conditions. This design introduces a new concept: pedestrians traveling between the vehicle left and through lanes (4). This includes the addition of a pedestrian facility between the DLT and the opposing through movement that travels away from the main intersection toward the crossover and bypass right lane end. This design places pedestrians in the median refuge island toward the crossover to cross the DLT there. The design, which functions similarly to the inside crossing option, creates a crossing opportunity across the DLT lanes at the crossover intersection because of the median positioning. This concept allows the channelized right-turn and DLT crossings to operate on the same signal phase, minimizing the number of signal phases needed to cross quadrants at the intersec- tion. Provided the two stages can be made within the provided clearance phase, the reduction in stages would reduce pedestrian delay at the main intersection.

8-18 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges Flag Remaining Description Mode/Travel Path Motor Vehicle Right-Turns (Section 4.4.1) Channelized right-turn lanes can lead to high vehicle speeds. This flag can be eliminated by signalizing the movement or reducing speeds below 10 mph with raised crosswalks or other methods. Pedestrians, all movements Nonintuitive Motor Vehicle Movements (Section 4.4.3) For pedestrians crossing the major street, crossing over the DLT is unintuitive. Although the conflict point is controlled, it may be unexpected and presents accessibility challenges. Pedestrians, major- street crossings Crossing Yield- Controlled or Uncontrolled Vehicle Paths (Section 4.4.4) If not signalized or stop-controlled, the pedestrian crossing of the channelized right-turn lane would result in a flag. Pedestrians and bicyclists, all movements Multilane Crossings (Section 4.4.7) The major and minor street pedestrian crossings include crossing over multiple lanes in a single stage and would be red or yellow flags, depending on subsequent design details. Pedestrians, all main intersection crossings Long Red Times (Section 4.4.8) Pedestrians may require multiple phases or cycles to cross the intersection, given the separation of many crossings of conflicting phases. This is amplified if the channelized turn lanes are signalized. Because the design is a partial DLT, the signal phasing would likely include three phases, increasing the relative red share during which pedestrians must wait. Pedestrians and Bicyclists, all crossings Motor Vehicle Left- Turns (Section 4.4.10) Users crossing the major street experience conflicts with the non- displaced left-turns from the minor street. Pedestrians and Bicyclists, major-street crossings 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, all crossings Exhibit 8-18. Summary of design flags remaining with DLT protected intersection concept.

Displaced Left-Turn (DLT) Intersections 8-19 The core elements of the design are as follows: • As with the inside crossing concept, the median walk provides a single crossing of mainline through vehicle movements. Limiting this crossing distance promotes a short clearance inter- val and cycle length, as well as reduced pedestrian crossing exposure. • A separate stage is necessary for crossing displaced left-turns and right-turns. An option is provided to make this crossing at either Location 1 or Location 2 in Exhibit 8-20. • Accessibility and pedestrian comfort are of concern for traversing the median between two opposing directions of traffic. • An optional side path is shown. Absent the optional side path, the corner pedestrian path shown would require two crossings. Exhibit 8-19. DLT pedestrian walkway between vehicle left and through lanes concept. Exhibit 8-20. Detailed view of median walkway. The median walk Pedestrian travel way Bicycle travel way

8-20 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges 8.4.3.1 Benefits This DLT intersection concept includes these benefits for bicyclists and pedestrians: • Multilane Crossings design flag: An inside crossing pedestrian mainline crossing minimizes crossing distance and exposure to vehicular traffic. A tapered median also allows for a rela- tively narrow median at the mainline crossing, to shorten the crossing distance. The median walk concept also provides opportunities for pedestrians to avoid delay while crossing. • 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. • Nonintuitive Motor Vehicle Movements design flag: If pedestrians are crossing the inter- section from west to east or east to west and are strictly using the median walk, they may avoid crossing over the displaced left-turns entirely. The use of the median walk would trigger the Executing Unusual Movements design flag (Section 4.4.6). • The provision of bike lanes on the minor street provides facilities suitable for highly confident cyclists, possibly inviting lower-confidence cyclists if motor vehicle volumes and speeds are appropriate. • The presence of the median walk would allow for the placement of a transit stop between the main and crossover intersections. The other DLT intersection designs would not allow for this because of the placement of the displaced left-turns between the through lane and walking paths. 8.4.3.2 Challenges The median walk concept leaves some design flags remaining, as presented in Exhibit 8-21. 8.5 Detailed Design Techniques The design flag procedure and corresponding flags are outlined in Chapter 4, and general design techniques are discussed in Chapter 5. Discussion in this section is limited to unique characteristics or design to assist in addressing flags at a DLT intersection. Specifically, the sub- sequent sections discuss the following: • Crossover/left-turn design approach; • Geometry and location of DLT; • Channelized vs. non-channelized right-turns; • Bypass lane design; and • Three-legged intersection. 8.5.1 Crossover/Left-Turn Design Approach The potential need for a bicyclist to cross through multiple lanes of concurrent through traffic to turn left is not a unique challenge for DLT intersections; however, the design of DLT inter- sections has rarely provided reasonable alternatives. One reasonable alternative is to provide a two-stage turn box (as exemplified for all bicycle left-turns in Exhibit 8-15 and northbound and southbound left-turns in Exhibit 8-22) to facili- tate left-turns made over two signal phases without a crossover. Alternatively, a DLT intersection can include a separated bicycle lane or shared-use path so cyclists can make the turn by crossing with pedestrians. To accommodate the bicyclist turning left with motor vehicle traffic, a controlled crossing for bicyclists could be placed at the entrance of the DLT. This would change the crossover conflict for the movement into a crossing conflict; the crossing could be uncontrolled depending on

(continued on next page) Flag Remaining Description Mode/Travel Path Motor Vehicle Right- Turns (Section 4.4.1) Channelized right-turn lanes can lead to high vehicle speeds. This flag can be eliminated by signalizing the movement or reducing speeds below 10 mph with raised crosswalks or other methods. Pedestrians, all movements Uncomfortable/Tight Walking Environment (Section 4.4.2) The careful design of the median walkway is necessary to mitigate the stress of walking between two sets of vehicle lanes. Pedestrians, median crossings Nonintuitive Motor Vehicle Movements (Section 4.4.3) For pedestrians crossing the major street, crossing over the DLT is unintuitive. Although the conflict point is controlled, it may be unexpected and presents accessibility challenges. Pedestrians, all origin-destination except crossing west to east or east to west using the median walks Crossing Yield- Controlled or Uncontrolled Vehicle Paths (Section 4.4.4) If not signalized or stop-controlled, the pedestrian crossing of the channelized right-turn lane would result in a flag. Pedestrians, all movements Multilane Crossings (Section 4.4.7) The minor street would require crossing over three lanes without refuge. Pedestrians, minor street crossings Long Red Times (Section 4.4.8) Pedestrians may require multiple phases or cycles to cross the intersection diagonally, given the separation of many crossings of conflicting phases. Because the design is a partial DLT, the signal phasing would likely include three phases, increasing the relative red share during which pedestrians must wait. Pedestrians, all crossings Motor Vehicle Left- Turns (Section 4.4.10) Pedestrians crossing the major street experience conflicts with the non- displaced left-turns from the minor street. Pedestrians, major- street crossings Sight Distance for Gap Acceptance Movements (Section 4.4.12) Adequate sight distance should be provided for any channelized turn movement not signalized. Pedestrians, all crossings Riding in Mixed Traffic (Section 4.4.14) The provision of on-street bike lanes on the minor street requires a bicyclist to ride alongside motor vehicle traffic entering, traversing, and exiting the intersection. The major street includes no bicycle facilities. Bicyclists, all approaches Exhibit 8-21. Summary of design flags remaining with DLT median walk concept.

8-22 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges Exhibit 8-22. Option for DLT crossing. Bicycle Clearance Times (Section 4.4.15) Bicyclists may not clear the intersection with the yellow and all- red phases programmed to accommodate vehicle trajectories. Bicyclists, through movements Lane Change Across Motor Vehicle Travel Lane(s) (Section 4.4.16) For any bicyclists who use the major street, there is no alternative left-turn provided other than using the DLT, which would require a crossover movement before the intersection to get into the left-turn lane. Bicyclists, major- street approaches Channelized Lanes (Section 4.4.17) For any right-turning bicyclists and major-street left-turn bicyclists using the DLT, channelized lanes force cyclists into a confined curve with motor vehicles. Bicyclists, right-turns and major-street left- turns Turning Motorists Crossing Bicycle Path (Section 4.4.18) Turning motorists cross the bike lane in this design with the development of the right-turn lanes. Bicyclists, all approaches Riding between Travel Lanes, Lane Additions, or Lane Merges (Section 4.4.19) For through bicyclists, the right-turn lane add before the intersection presents a diverging conflict point with motor vehicles. Downstream of the intersection, the motor vehicle right-turn reentry downstream of the intersection presents a merging conflict point. Bicyclists, through movements Flag Remaining Description Mode/Travel Path Exhibit 8-21. (Continued).

Displaced Left-Turn (DLT) Intersections 8-23 speed, volumes, and number of lanes (though it is expected the crossing would be best served as a controlled movement). In some DLT intersection designs, this would be a single-lane crossing. Speeds in the channelized left-turn and width of the lanes would be critical for bicyclist safety, with the possibility of adding a bike lane. This provision would improve access but might not satisfy the needs of risk-averse bicyclists. This concept is shown in Exhibit 8-22. 8.5.2 Geometry and Location of DLT Depending on its location (inside crossing versus outside crossing), the DLT can create way- finding and operational issues for pedestrians and bicyclists. People crossing between through and DLT movements may not intuitively know which crossings operate concurrently or in which direction traffic will be approaching. Additional wayfinding elements are advisable. 8.5.3 Channelized Versus Non-Channelized Right-Turns Most existing DLT intersections contain channelized right-turns either on some or all approaches, but some have been built without them. A general discussion of design flags and mitigation techniques for channelized right-turns is covered in Chapters 4 and 5. There are tradeoffs with either right-turn design approach. Channelized right-turns spread out vehicle-vehicle and pedestrian-vehicle conflict points and provide more capacity for right-turning motorists. However, they require additional right- of-way, may create additional exposure for crossing movements, may encourage high speeds through a pedestrian conflict point through their design, and introduce accessibility challenges for pedestrians with vision disabilities. A challenge particular to DLT intersections is that, with the displaced left-turn and associated medians, the inclusion of the right-turn lane without channelization may lengthen an already relatively long mainline crossing distance. This presents a challenge both for pedestrian exposure and for signal operations, given the required clearance interval. Another challenge of the non-channelized right-turn lane for motorists is the possibility for drivers to turn right into the upstream DLT lane (see Exhibit 8-23). Turning paths may be designed and demarcated to clearly define paths and discourage wrong-way right-turns, but this risk is unique to DLT intersections. As such, the channelized right-turn lane is expected to continue as a common feature at DLT intersections. The design of this channelized right-turn lane should consider the guidance in this document. Exhibit 8-23. DLT intersection with non-channelized right-turn.

8-24 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges 8.5.4 Bypass Lane Design If a bypass lane is used at a DLT intersection, there are two ways that DLT intersections have typically accommodated the geometry for the right-turn bypass lane to join back with the cross street through lanes. The choice between these two options will impact the pedestrian experi- ence if pedestrians are walking along an inside path between travel lanes. The on-street bicyclist experience will differ depending on the design. The two design options are to • Provide an add lane with a downstream lane merge. If an on-street bike facility is provided, then the corresponding through movement (shown as west to east in Exhibit 8-24) pres- ents an accelerating, merging bicycle-vehicle conflict point. With an off-street facility or path as shown, the bicycle movement will have crossed over the right-turn closer to the main intersection. • Signalize the movement and operate it as part of the crossover signal, as shown in Exhibit 8-25 and presented in all three design concepts in this chapter. A signalized right-turn approach as shown would provide a controlled vehicle-bicycle conflict point. RTOR movements could be allowed or restricted. With the provision of a separated bike facility, any ramp from the separated facility would be provided downstream of the signal to avoid a conflict with the right-turn in this location (This is shown for the minor street in Exhibit 8-15 previously in this chapter). 8.5.5 Three-Legged Intersection A three-legged DLT can provide crossing benefits for pedestrians and bicyclists. Traditional three-leg intersections often result in conflicts between pedestrians and vehicles turning left from the stem. The three-leg DLT allows for protected left-turns from the minor street to the major street as well as a protected crossing for nonmotorized users across the major street with no additional signal phase. Exhibit 8-25 shows an example of a three-leg DLT. Although access across the north-south roadway is not provided, it could be created between the northbound left and eastbound left. This would trigger the Indirect Path design flag. Exhibit 8-24. DLT with signalized right-turn entry.

Displaced Left-Turn (DLT) Intersections 8-25 8.6 References 1. Steyn, H., Z. Bugg, B. Ray, A. Daleiden, P. Jenior, and J. Knudsen. 2014. Displaced Left Turn Informational Guide. Report FHWA-SA-14-068. FHWA, Washington, DC. 2. Hughes, W. and R. Jagannathan. October 2009. “Displaced Left Turn Intersection” TechBrief FHWA- HRT-09-055. FHWA, Washington, DC. 3. Zlatkovic, M., and C. Kergaye. 2018. “Development of Crash Modification Factors for Continuous Flow Intersections.” Journal of Road and Traffic Engineering. Vol 64, No 3, pp. 5-11. 4. Chlewicki, G. 2014. “Using the Concept of the Continuous Flow Intersection to Improve Pedestrian Movements at Intersections.” Presented at Transportation Research Board Alternative Intersection and Interchange Symposium. Salt Lake City, UT. Exhibit 8-25. Median walk crossing option.