Transit-Supportive Roadway Strategies
Introduction
Because they typically operate in mixed traffic on open roadways, buses are much more susceptible than trains to delays. Slow speed and unreliable schedules are major problems for bus operators, as they raise cost, diminish service, and reduce public confidence in the network. In its report A Guidebook on Transit-Supportive Roadway strategies, the Transit Cooperative Research Program identifies strategies for improving bus service, grouped into four broad categories: bus operations, traffic control, infrastructure, and bus lanes.
Working with Roadway Agencies
Almost any project to improve bus service will involve working with a variety of partner agencies and stakeholders. At the top of this list are roadway agencies, which have authority over the roads that buses run on. Getting buy-in from roadway agencies can be a slow process. It’s smart to start on small projects that don’t ask a lot of the agency. Success at this stage can help sell agency leadership on the benefits of designing for better bus service.
When working with roadway agencies, it is important to be aware of the regulatory and policy environments. Transportation engineers are typically constrained to strict federal standards; projects that don’t comply will be non-starters unless clear documentation can justify a potential variance. And even when a project is compliant, that does not mean the roadway agency will support it. While some agencies are very supportive of transit, many view maintaining level of service for private automobiles as their main duty. In addition to starting small, ensuring that transit is a part of local long-range plans can help win roadway agency support.
Strategies
The heart of the guidebook is a collection of more than 30 different strategies for improving service. For each strategy, the guidebook outlines applications, costs and benefits, companion strategies, and implementation advice and examples.
Bus Operations Strategies
The guide begins with five operational strategies. These are good starting points for a transit agency, because they can be implemented with minimal roadway agency involvement.
- Stop relocation - Bus stops at the near side of intersections are more vulnerable to delays. In many cases simply moving the stop to the far side can improve schedule consistency.
- Stop consolidation - Unlike trains, buses tend to make frequent stops. While reducing the number of stops forces some riders to walk farther, savings in travel time make up for it.
- Route design - As cities evolve, old routes don’t always make sense. As a general rule, direct routes are desirable.
- Fare payment - Getting people on the bus faster means less dwell time. Cash payment is very slow; fare cards are faster, but even better is off-board fare collection with all-door proof-of-payment boarding.
- Vehicle changes - Different buses perform differently. One aspect of this to consider is that larger buses hold more passengers, but smaller buses accelerate more quickly and can make faster turns.
Traffic Control Strategies
Changes to traffic controls are another way to improve service. This will typically involve more cooperation with roadway agencies, but capital costs will generally be pretty low. It’s important to know that signal changes are constrained by the Manual on Uniform Traffic Control Devices (MUTCD). For cases where the MUTCD disallows a signal change that the agency thinks is desirable, the guidebook provides a template for a request to experiment to submit to the Federal Highway Administration.
- Movement restriction exemption - Many movement restrictions are safety-motivated, but others are simply meant to control traffic flow. The latter category can often be bypassed to improve bus routing.
- Turn restrictions - Getting stuck behind turning cars can be a major source of delay. Prohibiting turns has the potential to greatly improve service, as well as pedestrian safety.
- Yield to bus - When buses have to exit the travel lane to make a stop, getting back into the lane can be slow. A combination of laws and signs can potentially encourage drivers to let buses back into the lane more quickly.
- Transit signal priority (TSP) - Allowing buses to trigger changes in signal phase can improve their speed. Research conflicts about how effective this is, and it’s probably most easily justified for a bus rapid transit (BRT) project.
- Passive traffic signal timing adjustments - In the absence of TSP, general light retiming can improve bus service. This can be made more difficult by the fact that many lights are often linked and have to be adjusted together.
- Phase reservice - Giving buses a turn arrow both before and after the green light reduces delay. In some cases it can require investing in a new signal controller.
- Traffic signal shadowing - Turning left at an unsignalized intersection is often difficult. If traffic volumes do not warrant a signal, shadowing can be used to change a light downstream and create a gap in traffic for the bus.
- Pre-signals - Like shadowing, pre-signaling involves changing downstream signals. In this case it allows buses to move from a bus lane that runs between intersections to the general lane at an intersection.
- Bus-only signal phases - Sometimes it is possible to set signal phases that are only applicable to buses. This is particularly helpful for unconventional moves such as left turns from a right-side bus lane.
- Traffic signal installed specifically for buses - The MUTCD does not allow bus-only traffic signals to be installed based on traffic warrants, but pedestrian volumes and crash experience can potentially justify these signals.
- Transit signal faces - In cases where bus-only signals are implemented, there is a danger that they will confuse other motorists. The MUTCD provides for certain situations in which special signal faces can be used to prevent this confusion.
- Queue jumping - Queue jumps let buses get to the front of the line at an intersection. This can be accomplished by using a combined right turn lane or short bus lane or by letting buses temporarily drive on the shoulder.
- Traffic control enforcement - Many of these strategies do not work unless they are actively enforced. Police tend to put low priority on these issues. Automated enforcement is a good alternative, though often criticized as a cash grab.
Infrastructure Strategies
Physical roadway changes are another way to improve bus service. These will require the most work with the roadway agency and, generally, the largest capital expenditure. Bus lanes are the most obvious infrastructure strategy and will be covered in detail in the next section.
- Speed hump modifications - Buses accelerate and decelerate more slowly than other vehicles, so they are especially slowed by speed humps. Speed cushions are an alternative that slow most vehicles while allowing ones with wider wheelbases (buses, but also fire trucks and other emergency vehicles) to pass unencumbered.
- Bus stop lengthening - Delays are caused when too many buses use a stop. Stop lengthening often has to accompany stop consolidation. If service variability is causing the stops to be overcrowded, first try other strategies to improve consistency.
- Bus shoulder use - The shoulder of a divided highway can serve as a peak-period bus lane. In general, a minimum width of 10’ is required.
- Red-colored pavement - One way to signal that lanes are exclusively for buses is to paint them red. This is currently not allowed by the MUTCD and requires a request to experiment, but will likely become standard in the next version of the manual.
- Curb extensions - Leaving the travel lane to make a stop causes delays. Extending the curb into the parking lane allows buses to stay in the travel lane for stops. At intersections, curb extensions also reduce pedestrian crossing distances.
- Boarding islands - Boarding islands function like curb extensions, but can accommodate straight-moving buses next to right-turn lanes and left-side bus lanes.
- Bus-only links - Bus-only links are short sections of roadway that allow for more direct bus routing. Care must be taken to ensure that these links are clearly off-limits to general traffic.
Bus Lane Strategies
Giving buses dedicated roadway space is an obvious way to speed them up. Bus lanes can be full-time or only operate at peak hours. Peak-hour lanes might be easier to justify, but full-time lanes are easier to enforce. In either case, preventing turns across bus lanes makes them more effective.
- Curbside bus lanes - Curbside bus lanes can be created by converting parking lanes to bus lanes. The downside with curbside lanes is that there is lots of competition for curb space, and they are likely to be blocked by illegal stopping.
- Interior (offset) bus lanes - These lanes are usually directly to the left of a curbside parking space. They preserve curb space for other uses, but reduce roadway capacity by eliminating a general travel lane.
- Left-side bus lanes - Left-side bus lanes are useful when preparing for left turns. Limited-stop commuter buses sometimes will run on the left side. Left-side bus lanes require either boarding islands or special buses with left-side doors.
- Queue bypass - As mentioned, short bus lanes can be used to skip bottlenecks. This technique is useful at freeway meters.
- Median bus lanes - Median bus lanes run in the center of a roadway and are often separate by curbs or landscaped medians. They require a large right-of-way and dedicated signals, and are most commonly used for BRT.
- Contraflow bus lanes - Letting buses drive opposite the direction of traffic can allow for more direct routing on a one-way grid. They pose a danger in that drivers, pedestrians, and other road users might not expect a bus to come from that direction.
- Reversible bus lanes - Reversible bus lanes can be used in both directions. They pose the same safety risks as contraflow lanes, and can require significant frequency reductions.
Bicycles
The same roads that buses typically run on are often desirable bicycle routes. Managing bus and bike interactions can be a challenge. As mentioned previously, it is common for bus lanes to allow bicyclists. A shared bus and bicycle lane is better for both buses and cyclists than being in a general travel lane, but buses can get stuck behind cyclists. A wide lane allows buses to pass safely.
Bus stops pose a problem for cyclists when they require that the driver cut across the bike lane. Diverting the bike lane around the bus stop (either at grade or at sidewalk level) can be a good solution, though this opens the door to bike-pedestrian conflicts. In addition, care needs to be taken that the diversion does not impede the ADA compliance of the stop.
A Guidebook on Transit-Supportive Roadway Strategies
Additional Reading
Federal Highway Administration. "Manual on Uniform Traffic Control Devices." 2009.
- This document is the definitive source of federal standards on traffic control. All legal options for traffic control are outlined in the 800+ page MUTCD.