Published: January 20, 2023

9.1 General

This chapter focuses on pedestrian and bicyclist accommodations at interchanges and alternative intersections. This chapter expands on the general pedestrian facility guidance provided in Chapter 4, bicycle facility design guidance in Chapters 5 and 6, and motor vehicle facility design guidance in Chapter 7. Table 9-1 references the appropriate section in these chapters for design guidance at intersections.

Table 9-1: Cross Reference Table for Topics Mentioned in this Chapter

Designers should use this chapter to understand pedestrian and bicyclist safety and operations at interchanges and intersections but should consult the NCHRP 948 – Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges (2021) for more in-depth analysis of these issues and considerations.

9.2 Design Principles and Objectives

Interchanges and alternative intersections are typically implemented to increase motor vehicle safety and capacity and reduce motorist delay by adjusting the geometric features, signal operations, or lane utilization and configurations of a more traditional intersection. As a tradeoff, pedestrian and bicycle routes through interchanges and alternative intersections often become more challenging. At interchanges, there are often multiple intersections to navigate which may be paired with free-flow vehicular movements, typically higher traffic volumes and vehicle speeds, and the presence of larger vehicles. While the route through the intersection or interchange may vary from a traditional intersection, it is still imperative to follow best practices for pedestrian and bicycle outlined in this guide. These practices include minimizing conflict points, crossing lengths, and motorist speeds, providing logical routes to be taken across the intersection, and providing adequate sight distances.

9.2.1 Principles of Accessibility

The same principles of accessibility apply to pedestrian facilities at interchanges and alternative intersections as at traditional intersections. See Chapter 4 for a review of accessibility.

9.2.2 Design Considerations

At the start of any intersection design, the following questions should be asked:

• Can pedestrians and/or bicyclists travel safely and comfortably through the intersection?
• Is it clear to pedestrians and bicyclists when and where to cross?
• Will pedestrians and bicyclists approaching and within the crossing location be visible to drivers?
• What is the volume and speed of vehicular traffic at the crossing?
• Are all pedestrian facilities and crossings accessible?
• Where pedestrian and bicycle facilities interact, are these users visible to each other?
• Is it intuitive for pedestrians to determine the direction of traffic at crossing locations?

In order to address these questions, designers should consider three components of pedestrian and bicyclist travel: traversing, wayfinding, and crossing. Overall, the design of these facilities should consider alignments that address user comfort and sight distances, reduce motorist speeds at uncontrolled crossings, minimize the need for uncontrolled movements across crossing facilities, and provide appropriate buffer spaces between motorists and the non-motorized facilities.

Traversing

Traversing is the task of traveling through an interchange or intersection. It is important to develop a route that is as direct as possible and minimizes the number of crossings or the number of lanes crossed in a single movement. This is important because pedestrians and bicyclists desire to take the most direct route, or the route with least resistance, so the design should compel them to take the intended routes. Non-motorized users sometimes perceive large, complex intersections as too difficult to travel, and providing a complex route to navigate with multiple crossings further reinforces that negative perception. It is recommended that the designer balances the length of the route with the number of crossings.

Wayfinding

Wayfinding is the effort of identifying the intended route through an interchange or intersection. The more complex geometry of alternative intersections and interchanges can complicate wayfinding for nonmotorized users, especially for pedestrians with low or no vision. For all nonmotorized users, pedestrian and bicycle routes should provide adequate signage and striping. Wayfinding elements include signage, high-visibility crosswalks, colored pavement and striping to indicate dedicated space for bicyclists, directional markings to guide bicyclists to off-street facilities, detectable surfaces, lighting along the preferred route, buffer elements such as tree lawns when possible, raised elements such as curbs within median crossings to define boundaries and provide orientation elements, and accessible signals and pushbuttons.

Crossing

Crossing is the effort to cross the vehicular travel lanes in an alternative intersection or interchange. For pedestrians, it is critical to maintain an intuitive alignment through the crossing. Like wayfinding, this task can be more difficult for pedestrians with low or no vision. For bicyclists, crossing motorist lanes in an interchange or alternative intersection may involve additional striping to delineate specific locations for bicyclists to queue prior to crossing, or providing bicyclists with the opportunity to cross travel lanes before motorists enter the intersection. Since traffic may not approach from a typical direction it is also important to provide signage or cues for pedestrians and bicyclists at a crossing to alert them to what direction vehicles may be approaching from.

9.3 Interchanges

Specific design guidance for motor vehicles in interchange facilities can be found in the L&D Manual, Volume 1, Section 500. If a project is considering new or revised interchange features designer must review L&D Manual, Volume 1, Section 550 and provide all necessary documentation for review.

9.3.1 Diamond Interchanges

Diamond interchanges are the most common form of interchanges. Diamond interchanges allow for free-flow operation on the major highway but create at-grade intersections on the minor roadway with the ramps. Intersection control within these intersections may include uncontrolled (free- flow), stop control, signalized control, and yield control.

Pedestrian Considerations

At a diamond interchange, designers should follow the same intersection design practices detailed in Chapter 4 and detailed earlier in Section 9.2. A benefit of diamond interchanges is that pedestrians only need to look in one direction for oncoming traffic when crossing interchange ramps.

With the ramp geometry mimicking a conventional intersection, designers should follow the recommended design guidance in Section 4.4 for pedestrian facility consideration and design.

Bicycle Considerations

At diamond interchanges, bicycle accommodations are generally similar to typical on-road bicycle facilities detailed in Chapter 6 of this manual. Care should be taken when designing bicycle facilities considering the speed of motorists and the lengths of turn lanes where bicyclists may be located between through and right-turning motor vehicles. It may be beneficial to provide opportunities to exit the on-road facilities to a side path where turn lanes are very long or encourage high speeds for motorists. Designers will need to make it visually clear where bicyclists are to remain in the roadway with enhanced striping and/or colored pavement to avoid trapping the bicyclist. Information on pavement markings in areas where bicyclists and motor vehicles may conflict with each other can be found in Section 6.5.

9.3.2 Cloverleaf Interchanges

Cloverleaf interchanges often utilize free-flow loop ramps to accommodate left-turn movements between the major and minor roadway. These free-flow ramps allow motorists to execute these left turn movements without traveling through an intersection and are often designed to allow drivers to navigate the interchange without stopping. Full cloverleaf interchanges use these loop ramps in all four quadrants while partial cloverleafs use loop ramps in one to three quadrants and diamond interchange intersection control options for the other quadrants. However, the use of high-speed free-flow ramps runs counter to the principles of safely accommodating pedestrians and bicyclists.

Free-flow ramps at cloverleaf interchanges often result in acute intersecting angles that limit visibility, permit drivers to accelerate or continue at a higher operating speed through the intersection, and orient vehicles so that drivers may not be pointed toward pedestrian crossings or looking in an opposite direction for oncoming traffic. These skewed crossings can increase the time that pedestrians and bicyclists are exposed to motor vehicles.

Limiting bicyclist exposure to motor vehicles at free-flow ramps can be challenging. The most complicated part of accommodating bicyclists is determining how to continue bicycle facilities through weaving areas where the ramp merges or diverges from the adjacent roadway.

Pedestrian Considerations

There are multiple treatments that can be implemented to help improve pedestrian facilities within the interchange. Designers should implement high visibility crosswalks and install pedestrian warning signage, yield lines, and potentially rectangular rapid flashing beacons at uncontrolled crossings to warn drivers of the likely presence of pedestrians. Designers should also provide sidewalks through the interchange. Where adjacent land uses in the vicinity of the interchange are potential pedestrian generators, pedestrian facilities should be continuous along both sides of the interchange. Where it is determined that sidewalks should only be continuous along one sides of the interchange (e.g., to avoid a higher-volume, higher-speed free-flow ramps), designers should design the sidewalk network, approach roadways, and adjacent intersections to allow pedestrians to cross outside of the interchange area to the side where continuous sidewalk is provided.

Designers should consider treatments to slow traffic, improve sight distance, and encourage yielding to pedestrians in the intersection. By reducing speeds and improving sight distance, drivers have more time to react and yield to pedestrians waiting to cross or already crossing. Designing or reconstructing the on- and off-ramps from a free-flow condition to intersect the crossroad at an angle closer to 90 degrees with smaller radii reduces vehicular speeds and orients the driver to directly face the crossing location. If the control of ramps is modified, or the geometry of an interchange ramp is “squared up” closer to 90 degress, an Interchange Operations Study (IOS) or Interchange Modification Study (IMS) must be performed and coordinated with the Office of Roadway Engineering to confirm that the impacts are acceptable. See L&D Manual, Vol. 1, Section 550 for guidance.

Multi-lane right turns should be prohibited unless signalization is provided to eliminate the potential for the “multiple threat” scenario where one vehicle blocks the pedestrian from the sight line of a second approaching vehicle. Ensuring the crossing location is within the approach line of sight for drivers and meets stopping and intersection sight distance criteria is also critical to confirming pedestrians within the crossing are visible to approaching vehicles. Figure 9-1 illustrates some of these treatments for on-ramps, but similar treatments for lower-speed design can be used at off-ramps.

Bicycle Considerations

Providing clearly marked bicycle facilities through the free-flow merging and diverging areas at the ramp terminals is critical to improving visibility of the bicyclists and reducing exposure to vehicles exiting and entering the roadway. It is recommended that designers stripe entrance and exit ramps so through moving bicyclists do not have to weave across motorists and can continue traveling along the facility while turning motorists are required to yield (see Figure 9-1). This treatment is similar to the striping of on-street bicycle lanes at standard intersections where dedicated right turn movements are present to avoid a right-hook collision. It is also recommended to provide opportunities for bicyclists to leave on-street facilities and transition to a separated bike lane or shared use path. See Section 6.3.8 for guidance on transitioning bicyclists from on-street facilities to sidewalks to shared use paths. Figure 9-2 provides two striping and signing methods for accommodating bicyclists at exit ramps if the geometry of the ramp is unable to be designed closer to 90 degrees to the intersecting roadway.

Figure 9-1: Potential Bike and Pedestrian Treatments at Cloverleaf Interchange On-Ramps

Figure 9-2: Bike and Pedestrian accommodations at free-flow exit ramps

9.3.3 Single Point Urban Interchanges (SPUI)

A SPUI is a variation of a diamond interchange. L&D Manual, Volume 1, Section 501.2.1.2 provides design details for this type of interchange. The footprint of a SPUI is compressed to a single traffic signal, creating an “X”-pattern for vehicle traffic using the interchange ramps. With this interchange, right turn movements are often a free-flow maneuver to increase vehicular capacity and only the left turns pass through the traffic signal.

The biggest challenges to accommodating pedestrians at SPUIs stems from the sheer size of the interchange and resulting length of the pedestrian path of travel through the interchange, the number of conflicting signal phases, and uncontrolled crossing locations. Pedestrians are only able to cross a portion of the interchange in a single signal cycle and it might take as many as four phases to traverse the entire interchange if each crossing is signalized. Pedestrians may not desire the delay or additional effort to reach a crossing and may choose to cross outside of a crossing and signal phase, risking exposure to vehicles. Bicyclists face similar challenges to pedestrians when trying to navigate a SPUI. Due to the size of the intersection, bicyclists might have a difficult time clearing the intersection’s yellow and all red phase. Uncontrolled right turn lanes may also expose bicyclists to large mixing zones and areas of increased conflict with higher-speed vehicles.

Figure 9-3 highlights the challenges that pedestrians and bicyclists face at a SPUI.

Figure 9-3: Bike and Pedestrian Facility Challenges at a SPUI

Pedestrian Considerations

Options to address the challenges pedestrians face include providing a separated pedestrian facility (i.e., pedestrian bridge or underpass). This is the most expensive option, but it does reduce the chances for conflicts with vehicles and provides the clearest route for traversing the interchange. Other treatments include implementing high-visibility crosswalks and utilizing stop or signal control in lieu of free-flow right turn movements. Constructing crossings that intersect at 90 degrees will also help by reducing pedestrian crossing distances. Figure 9-4 shows a SPUI with pedestrian crossings with good alignment and high-visibility pavement markings.

Figure 9-4: SPUI with high-visibility and 90-degree pedestrian crossings
(Source Google Maps)

The designer will also need to consider how they route pedestrians through median islands within the interchange. These islands will be used as pedestrian crossing islands and should be designed as a comfortable and safe place for pedestrians to wait to cross. Channelizing elements such as curbing and low-height landscaping or barriers that do not block driver visibility can be considered to separate pedestrians from traffic and provide a clear pedestrian alignment through the islands. If an island is fully paved, curbing the pedestrian alignment or using different pavement textures may help pedestrians with vision disabilities better distinguish the pedestrian route.

Bicycle Considerations

Typically the volumes of motor vehicle traffic will provide sufficient minimum green time for bicyclists to cross the intersection. However, designers must ensure yellow and red clearance intervals are sufficient for bicyclists to cross the intersection (see Section 8.4.4). Providing a bicycle stop bar as close to the intersection as possible can help to reduce crossing distances. Putting the free-flow right turns under stop or signal control will help limit potential conflicts with vehicles since motorists will be forced to stop and check for bicyclists, pedestrians, and other motorists before completing their right turn. Reducing the number of free-flow right turns will also help to simplify the intersection and reduce potential bicyclist conflicts with motorists. Figure 9-5 illustrates various potential configurations for accommodating pedestrians and bicyclists at a SPUI.

If the control of ramps is modified, an IOS or IMS must be performed and coordinated with the Office of Roadway Engineering to confirm that the impacts are acceptable. See L&D Manual, Vol. 1, Section 550 for guidance.

Figure 9-5: Various Bicycle and Pedestrian Treatments at a SPUI

9.3.4 Diverging Diamond Interchanges (DDI)

DDIs are a variation of the traditional diamond interchange. These interchanges use directional crossover intersections to shift traffic on the minor roadway to the left-hand side of the roadway between the ramp terminals within the limits of the interchange. The crossover eliminates the need for left turn signal phases for the ramp terminals, simplifying the motorist traffic operations and reducing vehicular congestion. L&D Manual, Volume 1, Section 501.2.1.4 provides detailed design information and criteria for DDIs.

There are several concerns for pedestrians at DDIs. The signal phases are different from a traditional signal and may be challenging to interpret for pedestrians, especially pedestrians with vision and cognitive impairments if they are unfamiliar with the interchange. Pedestrians may find the orientation of traffic approaching the crossing to be unexpected due to the shifting of vehicular traffic to the left-side within the interchange. Finally, like a Cloverleaf interchange, there are free- flow movements with geometry that could result in high vehicular speeds and skewed crossings that can be difficult to provide adequate sight distances for pedestrians to negotiate the crossing. However, DDIs may offer benefits to pedestrians over a traditional diamond interchange by reducing the number of pedestrian conflict points.

For on-road bicycle facilities, there are several areas of concern. As bicyclists move towards the signalized ramp intersections, the weaving condition at the entrance ramp diverge can create conflict areas between vehicles merging onto the entrance ramp and the bicyclists maintaining a straight route through the interchange area. This vehicular movement and the potential conflict is similar to a right turn at an intersection and requires consideration of the location and delineation of on-road bicycle facilities. Another area of concern is within the interchange core, between the signalized ramp intersections. On-road bicycle facilities remain on the right-hand side of the travel lanes through the interchange. This results in the bicyclists shifting from the outside edge of the roadway to the interior of the roadway. On narrower roadway footprints with the interior area constrained by piers (when the highway passes overhead) or with oncoming traffic buffered only by the oncoming bicycle lane, the comfort level of a bicycle lane can decrease.

Pedestrian Considerations

With a DDI configuration there is an opportunity to provide two different pedestrian routes through the interchange: through the center of the interchange in the median within the interchange core or along the outside of the interchange like traditional interchange configurations. Table 9-2 highlights the advantages and disadvantages of the two route placement options. Figure 9-6 and Figure 9-7 show examples of pedestrian routes traveling along the outside of the DDI and through the center of the DDI.

Table 9-2: DDI Pedestrian Path Location Comparison

Figure 9-6: DDI showing pedestrian facilities along the outside of the interchange
(Source NCHRP 948: Guidance to Improve Pedestrian and Bicyclist Safety at Alternative Intersections)

Figure 9-7: DDI showing pedestrian facilities through the center of the interchange
(Source NCHRP 948: Guidance to Improve Pedestrian and Bicyclist Safety at Alternative Intersections)

Additional Pedestrian Crossing Considerations

When crossing the free-flow left turns and the walkway is along the outside of the interchange, place the crossing to allow for visibility between both the pedestrian and the motorist outside of the influence of bridge parapets, piers, or abutments. Crossing should not be placed too far upstream along the ramp where drivers are merging and may not be looking for a pedestrian as they are looking over their shoulder to find gaps in traffic coming from the free-flow off-ramp. Similarly, when crossing the free-flow on-ramp, place the crossing closer to the diverge point from the minor road at a point where vehicular speeds are reduced and where pedestrians are still easily in view for drivers that are looking ahead at the vehicles in front of them. When placing crossings, always ensure that the pedestrians can see the vehicles and that the drivers can see the pedestrians at each end of the crossing maneuver. When crossing through the center of the interchange, designers need to provide a wide enough walkway for the pedestrian to feel comfortable, as they are often have barriers and moving traffic on both sides of them. Eight to 10 ft. is recommended to easily facilitate two-way pedestrian traffic and reduce the feeling of being trapped between barriers. When negotiating bridge piers that may be in the center of the roadway and within the sidewalk area, make sure the walk is wide enough to provide an adequate Pedestrian Access Route (PAR) to accommodate wheelchair access around the piers within the sidewalk limits.

When placing pedestrian signals and detectors near the median nose, provide adequate space for the crossing island for a pedestrian waiting to cross in one direction while providing space for the pedestrian crossing from the other direction to access the walkway. Splitting pedestrian signals and detectors of differing signal phases onto separate poles is preferable.

Drainage may also be a consideration when placing walkways within the median areas. Typically, the medians serve as a drainage area for the DDI. Designers must make sure the walkway properly drains when located within the median. Designers should provide a buffer between the walkway and roadway whenever feasible to provide space for drainage structures and to reduce the spray from motorists onto the walkway.

Bicycle Considerations

There are three options for accommodating bicyclists at DDIs: marked bike lane through the DDI, shared use path, or a shared travel lane. With all three of these options, signal timing should be timed to accommodate a bicyclist through all movements and phases.

Bike lanes should be designed with the guidance detailed in Chapter 6 of this document. Bike lanes should continue through the entire interchange. Wider bike lane widths adjacent to concrete barriers will be appropriate to address bicyclist shy spaces (see Section 3.6.2). Where bike lanes cross exit ramps, green colored pavement could be considered to indicate to motorists that bicyclists might be present and to help guide bicyclists through the intersection. Figure 9-6 shows bicycle lane placement on the right-side of vehicular traffic through a DDI.

There are also four scenarios the designer could encounter that will impact how bike lanes are treated approaching the interchange: no dedicated right turn entrance ramp lane, dedicated right turn lane, outside through lane becomes entrance ramp/turn lane, and multilane entrance ramps

• No Dedicated Right Turn Lane: The bike lane will stay to the right-side of the travel lane. This is similar to how bike lanes are treated at traditional intersections where no right turn lanes are present. See Figure 6-6.
• Dedicated Right Turn Lane: The bike lane will be located between the through and right turn lane similar to traditional intersections where dedicated turn lanes are present. See Figure 9-1.
• Outside Through Lane Becomes Right Turn Lane: When the outside through lane becomes the ramp/turn lane, the designer will have to transition the outside bike lane to the left side of this turn lane. See Figure 6-38.
• Multilane Ramps: Where multiple lanes exit from the minor street to the ramp, particularly if the inside lane is a through/right lane, the outside bike lane should use a bike ramp (see Section 6.3.8) to transition to a shared use path (or sidewalk) to cross the ramp with pedestrians. Another bike ramp should be provided to transition the bicyclist back to a bike lane once the multilane conflict(s) have been crossed.

Transitioning the bike lane to a shared use path is noted above as the preferred design for some of the options, but providing a bike ramp to a shared use path should be considered for any option where the bicyclist would otherwise be exposed to high-volume or high-speed motorist traffic. Shared use paths or separated bike lanes can be provided as the preferred bicyclist accommodations through the interchange. The configuration of these bikeways will follow the same alignment as the pedestrian routes described in the Pedestrian Considerations narrative above and illustrated in Table 9-2. These routes can be located through the center of the interchange in the median within the interchange or along the outside of the interchange like traditional interchange configurations.

It is important to consider the transition of the bicycle facilities from the approaching roadway to the interchange area if the facilities are different from those provided within the interchange. If on-street bike lanes are present approaching the interchange but separated facilities are provided within the DDI, the facility transition should occur at the nearest intersection prior to the interchange, but must occur at least 100 ft. prior to the interchange. For more guidance on bike ramps, see Section 6.3.8. Designers can also transition between different types of on-street facilities. For example, if a shared lane is used prior to the interchange, designers may transition to a bike lane or separated bike lane through the interchange. If possible, this transition should be made at an intersection prior to the interchange if located nearby, but must occur at least 100 ft. before the crossover intersection.

If bike lanes will not be provided, highly confident bicyclists may choose to ride in the traffic lanes with motorists. If posted speeds are 35mph or less, shared lane markings can be implemented through the interchange to reinforce to drivers that bicyclists are legal road users and that they might be present in the travel lane.

9.4 Alternative Intersections

9.4.1 Median U-Turn (MUT) Intersections

MUT intersections eliminate turns at the main intersection on one or both of the intersecting streets with indirect left turns using a U-turn movement located downstream from the intersection. Typically, a wide median is needed to provide separation between directions of traffic and facilitate the left turning movements. Vehicles on the minor street that would turn left at a conventional intersection will instead turn right onto the major street and then make the U-turn movement. Signals at the main intersection facilitate through and right turns. On the major street, signals can be provided at the U-turn movements if appropriate. Figure 9-8 depicts the typical turning movements for a MUT intersection.

Figure 9-8: Median U-Turn Intersection Layout
(Source NCHRP 948: Guidance to Improve Pedestrian and Bicyclist Safety at Alternative Intersections)

Pedestrian crossings within a MUT are similar to a traditional intersection. The differences between a MUT and a traditional intersection are a reduction in the number of conflict points between pedestrians and motor vehicles within the major intersection, and the opportunity to utilize the U-turn median area as a mid-block crossing location. Challenges for pedestrian crossings include potential delay for vehicles on minor roadways if the crossing distance is long and requires additional time for the pedestrian WALK signal, and exposure to right turn conflicts. Bicycle facilities traversing through the intersection operate similarly to traditional intersections. Since MUTs shift left turns outside of the major intersection the resulting U-turn movement becomes a right turn at the major intersection, resulting in a high volume of right turning vehicles. The increase in right turn volumes causes an increase in potential conflicts with bicyclists traveling through the intersection.

Pedestrian Considerations

There are several considerations designers need to make when designing pedestrian accommodations in MUTs. At the main intersection, the wide medians present the option for pedestrians to cross in either one-stage or two-stages, but one-stage crossings are preferred. A one- stage crossing reduces pedestrian delay and does not require pedestrians to wait in the median to complete the crossing. Two-stage crossings may be necessary where the width of the major street may result in poor signal operations if required pedestrian walk times are longer than the green time needed for the vehicular movements on the minor street. Figure 9-9 shows the difference between a two-stage and one-stage crossing. For a two-stage crossing, staggered crossings or other alignment changes are not recommended. Strategies to reduce crossings from two-stages to one-stage include:

• Increase the cycle length, allowing the pedestrian to cross in one cycle.
• Reduce median width to shorten the overall pedestrian route and reduce pedestrian clearance time.
• Provide a pedestrian leading interval in the signal timing.
• Allow a pedestrian movement to alter signal phasing, which may temporarily alter signal coordination.
• Reduce the number of travel lanes or the widths of lanes and/or medians to reduce pedestrian clearance time.

Right turning movements and higher turning volumes at the main intersection also pose challenges to pedestrians. Designers should consider restricting right turns on red in order to increase safety and reduce potential conflicts between motorists and pedestrians. Designers should note, restricting right turns on red from the minor street may lead to increased conflicts with pedestrians crossing the major street. If the right turns use a channelized right-turn lane, pedestrian actuated signals or RRFBs may be used to bring attention to the presence of pedestrians.

The U-turn intersection is an additional opportunity to provide a signalized mid-block crossing. Typically MUTs only have signals that control that mainline traffic opposing the left turn as it approaches the U-turn intersection. By providing signals that control both directions of mainline traffic, a protected pedestrian crossing can be created.

For pedestrians with vision, mobility or cognitive disabilities, MUTs operate similarly to a traditional intersection. Providing clear delineation of the pedestrian route with curbing or landscaping can help facilitate navigation of the crossing. Developing a straight alignment between curb ramps from one area of the intersection to the next ensures pedestrians with disabilities can cross directly to a receiving curb ramp instead of wandering into the roadway, and it keeps the overall crossing distance to a minimum.

Figure 9-9: Crossing options at MUT intersection
(Source NCHRP 948: Guidance to Improve Pedestrian and Bicyclist Safety at Alternative Intersections)

Bicycle Considerations

Bicyclists making through movements typically have conflicts with an increased number of right turning vehicles in this intersection configuration because motorists use the right turn to complete an indirect left turn from the major road. Designers need to consider the potential vehicle and bicyclist conflict between right turning vehicles and through bicyclists. There are several potential solutions to address this conflict.

• One potential solution is to transition bicyclists to a separated bike lane or shared use path prior to the start of any motorist right turn lanes to allow bicyclist movements to be phase separated from right-turning motorists.
• Another solution is placing the on-street bike lane to the left of a dedicated right turn lane, as illustrated in Figure 6-36. This layout still requires a weaving location for right turn vehicles to cross the bike lane. Colored pavement should be considered in this scenario to highlight the potential conflict zone between drivers and bicyclists.

Bicyclists executing a left turn movement from either the minor or major street should be accommodated using either a two-stage left turn (see Section 6.5.1) or by following the pedestrian path of travel. Although bicyclists can legally make the left turn movement as a vehicle using the U-turn, this movement presents out-of-direction travel and increased conflict areas that should be avoided. Figure 9-10 below illustrates each of these crossing alternatives from the minor to major street.

When specifying the use of shared use paths at MUTs, a bike ramp from the on-road facility to the shared use path is required. For guidance on bicycle ramps, see Section 6.3.8.

Figure 9-10: Left Turn options for bicycles
(Source FHWA Median U-turn Intersection Informational Guide)

9.4.2 Restricted Crossing U-Turn (RCUT) Intersections

RCUT intersections eliminate left turn and through movements from cross street approaches at the intersection. To facilitate these cross-street movements, minor street drivers are required to turn right onto the major street and then make a U-turn maneuver at a one-way median opening downstream of the main intersection. Figure 9-11 illustrates the general movement of motorists navigating through and turning movements in the intersection.

RCUT intersections are typically considered on median-divided highways with heavy through and/ or left turn volumes on a major street and low through and left turn volumes from a minor streets. RCUT intersections can have three or four approaches and can be signalized, stop controlled, or merge/yield controlled. Signalized RCUTs are typically part of a synchronized corridor while stop controlled RCUTs are usually at isolated intersections on four-lane divided arterials. Merge/yield controlled RCUTs are typically seen in rural high-speed corridors similar to freeway corridors.

For motorists, the benefit of an RCUT is improved safety through the reduction of conflict points between motor vehicles, increased efficiency since each direction of the main street can operate independently, and fewer signal phases which reduces delay.

For pedestrians, the RCUT’s typical configuration differs substantially from crossings at traditional intersections. The “Z” crossing configuration (see Figure 9-12) results in out-of-direction travel, increasing pedestrian exposure and delay. The signal timing can also cause pedestrian delay by preventing a single stage crossing. Pedestrians with visual disabilities may also have difficultly discerning the movements through the intersection. Compared to a traditional intersection, RCUT intersections typically increase the volume of right-turning motorist, which can increase pedestrian exposure to turning vehicles.

Figure 9-11: Restricted Crossing U-Turn Intersection Layout
(Source NCHRP 948: Guidance to Improve Pedestrian and Bicyclist Safety at Alternative Intersections)

Within a typical RCUT, bicyclists can travel either on a shared use path or within the roadway. With on-street facilities, bicycle left turn and through movements on the minor approach follow the same route as a vehicle through the U-turn to navigate the intersection. This movement is significantly different from a traditional intersection and requires multiple weaving maneuvers across vehicular lanes, increasing the number of conflict points between a bicyclist and vehicle, and increased out of direction travel. There are no clear routes for these movements from a minor street for bicyclists without modifying the RCUT design. Bicycle right turns can conflict with pedestrians and the high right-turn vehicular volumes. If channelized lanes are provided on any approach, there are increased conflicts related to the bicycle facilities crossing the channelized lanes.

Pedestrian Considerations

With the unique layout and motor vehicle movements in an RCUT, providing highly visible, clearly defined spaces for pedestrian crossings is critical to pedestrian safety and motorist recognition. Designers should consider the orientation of vehicles approaching pedestrian crossings to ensure sight lines are clear for the driver to easily see a pedestrian at the edge of the roadway waiting to cross and within the crosswalk itself.

To overcome the wide geometric footprint that can impact pedestrian crossings, short cycle lengths can break-up the pedestrian crossing across individual directions of travel, creating crossings that are comparable to crossing times at traditional intersections. Designers will also need to ensure that crossings are accessible for all users, especially pedestrians with vision disabilities. Designers should include audible devices, channelization, and other techniques described earlier in this guide to delineate the pedestrian route and crossing.

With higher right turning volumes, it is recommended to control right-turn movements to protect pedestrians. If concurrent motorist/pedestrian movements are allowed, the curb radius should be as small as possible to reduce turning vehicle speeds and shorten the pedestrian crossing distance. If the right turn is designed as a channelized turn lane, the median island should be large enough for pedestrians to queue with geometry consistent with Section 7.2.6.

Wayfinding signing and other wayfinding devices will be critical to help direct pedestrians through the intersection. Other tools such as curbs and landscaping can be used to channelize pedestrians to the intended crossing locations.

The “Z” crossing, shown in Figure 9-12, is a typical method for accommodating pedestrians at RCUT intersections. Pedestrians cross the minor streets in the same manner as a traditional intersection. However, when pedestrians cross the major street, they take a less traditional crossing through the median created by the opposing left turn lanes from the major street. This is a longer route than at a traditional intersection to cross from A to D, but a shorter route to cross between B and C. Natural pedestrian design lines should be considered based on adjacent land uses, transit stop locations, etc. to identify whether this pedestrian routing is appropriate for the expected pedestrian activity.

Figure 9-12: Pedestrian “Z” Crossing at RCUT Intersection
(Source NCHRP 948: Guidance to Improve Pedestrian and Bicyclist Safety at Alternative Intersections)

Besides the “Z” crossing, pedestrians can cross RCUT intersections with a median crossing and a Barnes Dance. Table 9-3 depicts the various crossing options as well as the estimated travel time and delay pedestrians might experience. Mid-block crossings at the U-turn intersections should be considered at all RCUTs to supplement the main intersection crossings so that some pedestrians can avoid having to make the “Z” crossing. Median crossings are preferred at RCUT intersections with offset minor streets, but suitable pedestrian queuing areas need to be provided. A staggered crossing can also be implemented in the median depending on how offset the minor streets are from each other. For more guidance on staggered crossings, see Section 9.4.4. Another option at the main intersection of the RCUT is an exclusive pedestrian phase. As discussed in Section 8.3.4, exclusive pedestrian signal phasing can increase delay for both motorists and pedestrians and is only appropriate if the pedestrian volumes are significant.

Table 9-3: Crossing options at RCUT intersections (Source FHWA Restricted Crossing U-turn Informational Guide)

Crossing Type	Illustration	Mean Travel Time per Pedestrian (sec)	Mean Total Delay per Pedestrian (sec)
"Z"		465	132
Signalized Mid-block		479	119
Median Cross		487	160
Exclusive Pedestrian Phase		422	102

Bicycle Considerations

In an RCUT intersection, bicyclists can be accommodated in on-street bike lanes and shared use paths. Shared use path accommodations and crossings should be designed with the same considerations as typical pedestrian facilities. For on-street bicyclists the design will vary depending on if the bicyclist is on the major or minor street. In all cases, designers should consider providing bike ramps to allow on-street bicyclists to choose to exit on-street facilities prior to the intersection and return to on-street facilities after the intersection (see Section 6.3.8).

For bicyclists on the minor roadway, there are three ways to accommodate through and left turning movements as described below and depicted in Figure 9-13:

• Using a “Z” crossing (if provided).
• Using a more direct crossing route (if provided).
• Using a route similar to motor vehicles using the U-turn.

For bicyclists who choose to stay in on-street facilities on the major street, through and right turning users have a similar experience to traditional intersections, but typically have more green time to execute their maneuvers. For bicyclists on the major roadway wishing to turn left onto the minor street, the use of the “Z” crossing provides the most direct path of travel and should be accommodated. While Highly Confident Bicyclists might use the left turn lane with other vehicles, Interested but Concerned Bicyclists are more likely to exit at a pedestrian crossing and cross as a pedestrian. Finally, if the more direct crossing route discussed above is provided for the minor street, this crossing can also accommodate the left turn movement from the major street using a two-stage turn box located on the minor street. Wayfinding signing should be used to convey the available options to bicyclists.

Figure 9-13: Bicycle Crossing Options at an RCUT Intersection
(Source NCHRP 948: Guidance to Improve Pedestrian and Bicyclist Safety at Alternative Intersections)

As with pedestrians, it is imperative to provide high visibility markings that can be easily seen by both bicyclists and motorist. The bicyclist’s route through the intersection should be easy to follow and weaving areas between bicyclists and motorists clearly delineated so both road users are aware of the potential presence of each other.

9.4.3 Displaced Left Turn (DLT) Intersections

A DLT intersection, or a Continuous Flow Intersection (CFI), is an at-grade intersection that relocates left turns to the right side of opposing traffic with a crossover intersection upstream of the main intersection. By moving the lefts to the right side of opposing traffic, all movements on the major street can proceed simultaneously, eliminating the need for a separate left turn phase. Figure 9-14 below summarizes the vehicle movements at the intersection.

The goal of a DLT intersection is to reduce signal phases to reduce intersection delay for motorists and achieve higher vehicle capacity than a traditional intersection. However, this configuration and signal phasing creates tradeoffs for bicycle and pedestrian accommodations.

Figure 9-14: Displaced Left Turn Intersection Layout
(Source NCHRP 948: Guidance to Improve Pedestrian and Bicyclist Safety at Alternative Intersections)

Pedestrian Considerations

Pedestrian movements at DLTs are often significantly longer than at traditional intersections because they have to cross multiple vehicle lanes and medians. There are two typical crossing options for pedestrians at DLTs: an outside crossing or an inside crossing. Designers have the challenge of creating a reasonable route that minimizes travel time for pedestrians in both options.

Outside Crossing

For the “Outside Crossing,” pedestrians cross the minor street on a route that is to the left of the displaced left turn movement for the major street. Figure 9-15 illustrates this type of crossing as movement “b.”

There are several key elements to this crossing option. Pedestrians crossing the minor street are competing for green time with the displaced left turns from the major street. A leading or lagging turn phase could be implemented to avoid having pedestrians and the left turns cross at the same time. Designers should note that if there are dual-left turn lanes, a protected only left-turn phase would be required. When crossing the major street pedestrians may have vehicles approaching from the right in the nearest lane, which is an unexpected direction and may not be understood by pedestrians with vision or cognitive disabilities. The outside crossing can result in long crossing times and slower pedestrians may not be able to make the entire crossing in one cycle, making the crossing time even longer. For these reasons, the outside crossing is recommended when crossing lengths are relatively short.

Figure 9-15: DLT Outside Crossing
(Source NCHRP 948: Guidance to Improve Pedestrian and Bicyclist Safety at Alternative Intersections)

Inside Crossing

Inside crossings provide crossing islands that separate the displaced left turns from the major street through movements. Figure 9-16 illustrates this type of crossing as movement “b.”

The inside crossings provide a shorter crossing distance from the main intersection; however, this approach may require multiple signal phases. These shorter crossings may benefit pedestrians, especially pedestrians with disabilities and slower walking speeds by providing more refuge locations.

In addition to deciding between inside and outside crossings, designers must consider the right- turn vehicle movements. Designers will determine if the right turns are signalized or not. If crossings are not signalized, designers must consider the method of traffic control, motorist speeds, and visibility to reduce the potential risk for pedestrians.

For both crossing options, channelization methods such as curbs, landscaping, and other methods previously mentioned should be used to direct and channelize pedestrians through the intersection. Due to the complex nature of the crossings, wayfinding signage should be provided.

Figure 9-16: Inside Crossing at DLT Intersection
(Source NCHRP 948: Guidance to Improve Pedestrian and Bicyclist Safety at Alternative Intersections)

Bicycle Considerations

Designers have a few options for accommodating bicyclists at DLT intersections. For on-street bicyclists, an inside crossing with two-stage left turn bike boxes might be preferred. As shown in Figure 9-16, space is generally available to accommodate the bike box in front of the median that separates the displaced left-turning traffic from the through traffic on the major roadway. The outside crossing does not often provide a convenient or comfortable location for a two-stage left turn box between the through movement and the displaced left turn movement.

Bicyclists can also be accommodated on a shared use path and cross with pedestrians in both outside and inside crossing options as shown in Figure 9-15 and Figure 9-16.

Designers will also need to consider the bicyclist movements when determining cycle lengths for the intersection. Short cycle lengths that allow adequate clearance time are critical for bicyclists. Two-stage left turns or utilizing the pedestrian crossings can be subject to additional delay. Limiting delay will encourage bicyclists to use the facilities as intended. The large footprint of the intersection also means that the designer will need to ensure if the clearance interval is appropriate for bicyclists (see Section 8.4.4).

9.4.4 Roundabout Intersections

Roundabouts are generally circular shaped, yield controlled intersections that contain one or more circulating lanes around a central island traveling counter-clockwise. L&D Manual, Volume 1, Section 403 provides guidance on roundabouts. NCHRP Report 672 Roundabouts: An Informational Guide, Second Edition and the Manual on Uniform Traffic Control Devices also provide guidance on roundabouts.

With roundabouts, entering traffic yields to circulating traffic. The circulatory roadway geometry is designed to maintain low vehicular speeds, reducing crash severity for motorists in the intersection. A raised or painted splitter island is provided on all approaches to separate entering and exiting traffic. The curved geometry of the splitter islands aligns traffic with the circulatory road and promotes lower speeds for motorists entering and exiting the roundabout. Roundabouts are generally easier and safer for pedestrians and bicyclists to navigate because motorist speeds are low and the raised splitter islands create a two-stage crossing that allows pedestrians to focus on one direction of traffic at a time while also shortening the crossing length. Where fastest-path analysis shows that motor vehicles may be faster than desired for pedestrian conflicts, designers should consider adjusting the geometry, providing raised crosswalks, and/or provide truck aprons along the right-side of the rightmost lane to encourage slower speeds.

For pedestrians with vision disabilities, the circular geometry of a roundabout can present challenges as they may be unable to decipher the approaching vehicle from the circulating vehicles or know when vehicles have yielded. Bicycle facilities approaching a multilane roundabout also require consideration to provide bicyclists with alternatives to navigate the circulating roadway with minimal conflicts from motor vehicles. Given the challenges that multilane roundabout create for pedestrians and bicyclists, if traffic projections show that multilane roundabouts may be needed in the future, designers should consider constructing single lane roundabouts that would not preclude multilane construction if and when that additional capacity is needed.

Pedestrian Considerations

Compared to traditional intersections, roundabouts are generally easier and safer to traverse. Roundabouts break the pedestrian crossing into two stages, providing a refuge in the splitter island. While the navigation of a roundabout may be easier for many pedestrians, pedestrians with vision disabilities may struggle with the non-traditional layout of the roundabout. With a traditional intersection, the sound of a vehicle traveling through the intersection or making a right turn is distinct. Pedestrians with vision disabilities can generally distinguish the direction that approaching vehicles are coming from and how quickly or slowly vehicles may be approaching. With the circular geometry of the roundabout, vehicles passing the exit legs of a roundabout can sound like an approaching vehicle that then turns away. This variation in sound may be hard to distinguish from a vehicle that is actually exiting the roundabout if the pedestrian crossing is too close to the circulatory roadway. To overcome these concerns and to facilitate all pedestrian movements, designers need to ensure good channelization, proper alignment, and careful placement of the crossing.

The pedestrian crossing is typically placed 1 car length (20 ft.) back from the yield line on the entrance leg of the roundabout. This distance is far enough from the circulating roadway that pedestrians with vision disabilities can focus on the sounds of vehicles approaching or exiting the roundabout rather than the circulating traffic. The crossing should also be placed to maximize sight distances so motorists can see and stop before reaching the crossing when a pedestrian is present (follow the stopping sight distance criteria found in L&D Manual, Volume 1, Section 201.2). When developing the profile for the approach or exit of the roundabout, designers should take care not to place low points within the pedestrian crossing. Low points should be located at least 10-15 ft. away from the pedestrian crossing area to reduce the chances for water ponding or freezing in the pedestrian crossing.

The pedestrian route through the splitter island should be at least 6 ft. long and 5 ft. wide to serve as a pedestrian island. The longer and wider the crossing area, the more storage and pedestrian activity that can be accommodated. If bicyclists are expected to also use the crossing, the width should be at least 10 ft. wide and a length of 10 ft. should be considered to accommodate bicyclists with trailers. The pedestrian refuge through the splitter island should generally be at a similar elevation as the adjacent roadway, as opposed to ramping up and down with conventional curb ramps. The alignment of the pedestrian crossing can be designed three ways: straight, angled, and staggered.

• Angled crossings (see Figure 9-17) are the preferred configuration for pedestrian crossings, especially at higher volume roundabouts. The curb ramps are oriented perpendicular to the curbs, creating an alignment to the sidewalk that is more typical to a standard intersection and providing the shortest crossing distance. For multilane roundabouts, these crossings also better separate potential pedestrian pushbuttons in the splitter island. To help pedestrians better align with the crossing, the angle point within the splitter island should be well defined, as opposed to curved and subtle.

Figure 9-17: Angled Roundabout Crossing
(Source NCHRP 834: Crossing Solutions at Roundabouts and Channelized Turn Lanes for Pedestrians with Vision Disabilities)

• Straight alignments (see Figure 9-18) typically keep pedestrians aligned in one direction through the entire crossing. This alignment results in longer crossing distances across the travel lanes and requires directional curb ramps (see Section 4.5.9). A straight crossing is also more likely to be treated by a pedestrian as a one-stage crossing (i.e., pedestrians may continue to cross without stopping in the pedestrian refuge.) This design should generally be avoided except in unique circumstances, such as compact roundabouts with narrow splitter islands where it may not be possible to provide a pedestrian refuge.

Figure 9-18: Straight Crossing at Roundabout
(Source NCHRP 834: Crossing Solutions at Roundabouts and Channelized Turn Lanes for Pedestrians with Vision Disabilities)

• Staggered crossing alignments (see Figure 9-19) have different offsets from the circulating roadway on the entry and exit lanes. The pedestrian refuge within the splitter island must be designed with a minimum 5 ft. wide walkway that connects the two crossings, with wider widths necessary in areas of higher pedestrian volumes or where a shared use path is provided. Staggered crossings indicate to pedestrians that there are two separate stages to the pedestrian crossing. It also provides the most separation between pedestrian pushbuttons and signal heads if Pedestrian Hybrid Beacons are provided. It is recommended to offset the crossing on the exit leg farther from the circulatory roadway to allow for more vehicle storage, reduce the potential for vehicles queuing into the intersection, and provide more stopping distance for motorists to yield. Typically, the offset crossing of the exiting leg is placed 40 to 50 ft. from the circulating roadway. This separation from the circulatory road also benefits pedestrians with low or no vision as they can more easily decipher the sound of a vehicle exiting the roundabout from the circulatory roadway. Channelization with curbs or landscaping may be appropriate to discourage pedestrians from crossing at unexpected locations. These crossing applications are most appropriate at high volume, multilane roundabouts, especially where the splitter islands are wide and can easily accommodate the transitional area between the crossings.

Figure 9-19: Staggered Roundabout Crossing
(Source NCHRP 834: Crossing Solutions at Roundabouts and Channelized Turn Lanes for Pedestrians with Vision Disabilities)

Accommodating Pedestrians with Vision Disabilities

Visual cues are important factors for pedestrians navigating crossings at a roundabout. Pedestrians are tasked with looking for motorists yielding (or gaps in traffic) that will allow them to cross. This is much more difficult for pedestrians with visual disabilities due to free-flowing traffic and the absence of typical audible and tactile cues. Typically crossing a single lane roundabout does not present significant challenges, but multilane roundabouts are much more difficult to cross.

NCHRP Report 834: Crossing Solutions at Roundabouts and Channelized Turn Lanes for Pedestrians with Vision Disabilities presents guidance for accommodating pedestrians with vision disabilities at roundabouts. To accommodate these pedestrians, enhanced facilities need to be constructed to create a crossing that is accessible. This report highlights facilities that may provide equivalent facilitation of crossings consistent with the draft PROWAG accessibility guidance for pedestrians with vision disabilities.

When considering multilane roundabouts as a design alternative, it is vitally important to consider how pedestrians of all abilities will be accommodated. Draft PROWAG R306.3.2 states that at multilane roundabouts, pedestrian crossings will require a pedestrian activated signal for each crossing stage, including in the splitter island. A pedestrian hybrid beacon (PHB) is an appropriate signalization treatment, however they are expensive and if overhead wayfinding signage is provided, a PHB can create additional visual clutter for motorists. Motor vehicle operations must also be a consideration when determining if a multilane roundabout with PHB’s is an acceptable design solution and should be compared to the motorist operations if instead a single lane roundabout were provided. PHB warrants identified in the OMUTCD (Chapter 4F) should be followed when determining if a PHB is an appropriate signalization option for the pedestrian crossing. Multilane roundabouts that do not include accessible pedestrian signals should be designed to not preclude the ability to add them in the future.

Rectangular rapid flashing beacons (RRFB) with audible devices are not PROWAG compliant but do enhance accessibility. For additional information on using RRFBs at roundabouts to improve accessibility designers should refer to FHWA Publication No. FHWA-SA-15-069: Evaluation of Rectangular Rapid-Flashing Beacons (RRFBs) at Multilane Roundabouts. RRFBs are typically mounted on poles on the side of the roadway but can also be mounted overhead.

Additional non-signalized treatments can also be considered to improve accessibility. These treatments include raised crosswalks and speed tables to help reduce the speeds of motor vehicles at pedestrian crossings. Section 7.8.3 provides guidance on the design of speed tables and raised crosswalks. The orientation of these elements in a roundabout should center the pedestrian path on the curb ramp. See Table 9-4 for a summary of potential roundabout crossing enhancements discussed in this guide.

When designing raised crosswalks, the designer will need to consider the geometrics design and grade break alignment of the raised crosswalks, as well as other factors such as drainage impacts.

It is recommended to pair raised crosswalks with RRFBs to bring greater attention to pedestrians. Designers should work to reduce visual clutter and only provide necessary signage and markings to bring attention to the crossing. In addition to the design of the pedestrian crossing, designers also need to consider the sidewalk alignment within the intersection and leading to the crossing locations. When pedestrian accommodations at roundabouts are provided, it is recommended to provide a buffer between the sidewalk and the curb to help define the crossing locations.

The context of the project location, existing pedestrian accommodations, expected pedestrian activity, land use near the intersection, and community engagement should all factor into how pedestrians of all abilities are accommodated at multilane roundabouts.

Table 9-4: Roundabout Crossing Enhancements

Bicycle Considerations

Typically, with single lane and compact roundabouts it is recommended to merge on-street bike facilities with motorist traffic so bicyclists travel through the roundabout in a shared lane. Additionally, the OMUTCD, Section 9C.04, states that bike lanes are not to be located within the circulatory roadway of a roundabout. While Highly Confident and Somewhat Confident Bicyclists may be comfortable traversing a roundabout in a shared lane environment, many bicyclists will not feel comfortable navigating roundabouts with higher motorist volumes, especially multilane roundabouts. For user comfort, roundabouts should also be designed to facilitate bicycle travel outside of the circular roadway on a separated bike lane or shared use path. Where shared lanes or bike lanes are provided on the approach to a multilane roundabout, it is recommended to transition on-street bicyclists to a separated facility.

This transition from on-road to separated bikeway shall be located as per OMUTCD 9C. If on-street bike lanes are present, they shall be terminated in advance of the roundabout at the transition to the separated bikeway. As shown on Figure 9-20, if the elevation of the separated bikeway differs from the on-road facility, a bicycle ramp must be provided to transition between these facility types. The bike lane line should be dotted for 50 to 200 ft. in advance of the taper to provide guidance to bicyclists who wish to travel the roundabout in the shared lane.

Figure 9-20: Bicycle Lane Transitions and Striping at a Multilane Roundabout

When separated bike lanes are provided on approaches to roundabouts, they may be continued around the intersection to maintain the continuity of the bikeway. When bike lanes are provided on approaches to roundabouts, and if it is desirable to maintain separation between bicyclists and pedestrians, the bike lanes may transition to separated bike lanes around the roundabout. Figure 9-21 provides an example of a separated bike lane at a single lane roundabout.

Figure 9-21: Bike Lane Transition to Separated Bike Lane at a Roundabout