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40 4.1 Overview This guidebook identifies 34 different strategies that can directly improve bus speeds or reli- ability or that can help support other strategies in reaching their full effect. As there are many possible causes for speed and reliability problems, and most strategies focus on a particular issue, it is important to understand the cause of the problem (see Section 3.3) prior to starting to identify potential solutions. In addition, understanding the local policy (Section 3.2) and regulatory (Section 3.4) environments will help to narrow down the list of candidate strategies to ones that can be implemented in the local context. This chapter provides guidance on (1) potential criteria to use for selecting strategies and (2) matching strategies to causes of bus speed and reliability issues. 4.2 Potential Selection Criteria Traditional Approach Many reference documents have recommended specific bus volume âwarrantsâ for constructing transit-specific roadway strategies, in particular bus lanes. All of these warrants can be traced back to the same source, NCHRP Report 155: Bus Use of HighwaysâPlanning and Design Guidelines (Levinson et al. 1975). Although NCHRP Report 155 was careful to note that environmental and policy considerations, as well as the ability of other streets to accommodate diverted traffic, could result in lower warrant volumes, this guidance has not always been carried through to later docu- ments. The stated philosophy underlying the NCHRP Report 155 warrants is that the number of people using a bus lane should at least equal the number of people served by a general traffic lane; however, at least in some cases, these minimum bus volumes result in considerably higher person volumes in the bus lane relative to a typical urban street general traffic lane. One problem with using the NCHRP Report 155 bus volume warrants is that they assume a particular policy environment; namely, one where jurisdictions provide transit priority only when transit use is already so high that a de facto bus lane is created by the presence of the num- ber of buses needed to serve those passengers. However, jurisdictions may have other priorities (e.g., minimizing person delay, increasing non-automobile mode share, reducing automobile emissions) that are not considered by this approach or are even worked against by this approach. Jurisdictions may also wish to prioritize different modes on different streets, and a one-size-fits-all approach to selecting transit-supportive strategies does not fit well with this desire. A second problem with applying warrants is that traffic engineers understand a warrant to be a minimum, but not necessarily sufficient, criterion for justifying a traffic control or roadway design feature. If the warrant is not met, the feature would not be provided. Thus, applying rigid C H A P T E R 4 Selecting an Appropriate Strategy
Selecting an Appropriate Strategy 41 warrants can often work against a jurisdictionâs desire to improve transit service because the warrants may suggest that bus volumes are insufficient to justify the strategy, even though other factors may well suggest that the strategy will provide a net benefit to the community. Transportation engineering practice has been evolving in recent years toward a more flexible approach to evaluating potential roadway design strategies, as evidenced by the Context Sensitive Solutions (FHWA 2014) and Complete Streets (Active Transportation Alliance 2012) movements. A review of transit-supportive roadway strategies implemented by 52 transit agencies in the United States and Canada (Danaher 2010) found that nearly all considered multiple factors when evaluating strategies and did not apply the NCHRP Report 155 warrants. The most recent guidance documents, such as AASHTOâs transit design guide (2014), also suggest considering a range of factors when evaluating potential strategies. This guidebook follows that approach. Comprehensive Approach The decision to implement a transit-supportive roadway strategy needs to take into consideration and balance the needs and desires of the transit agency and its passengers, other roadway users, and the community as a whole. Consequently, multiple decision-making criteria are suggested. From the transit agency perspective, AASHTO (2014) identifies the following principles as potential reasons for justifying transit-supportive strategies: â¢ Provide priority to road users using less-polluting, more space- and energy-efficient, and less-costly (to society) travel modes; â¢ Allocate roadway delay proportionally among all roadway users; â¢ Protect the public investment in transit service; and â¢ Give an advantage to vehicles that maximize person throughput. As the transit agency is frequently responsible for the cost of implementing transit-supportive strategies, the cost of implementing the strategy relative to its benefits is an important consideration. The less expensive the strategy, the more passengers it benefits, and the less the strategy affects other road users, the more likely it will be to show a net benefit. From the roadway agency perspective, the roadway operations and design standards applied to the project will set the frame for what may or may not be possible to implement, considering transit and general traffic delay, road user safety, and pedestrian and bicycle accommodations, among other factors. The community perspective will consider such factors as: â¢ Improvements to the communityâs mobility options, â¢ Support for the communityâs long-term economic development vision, â¢ Support for community goals to promote greater use of non-automobile modes, and â¢ Environmental impacts (AASHTO 2014, Kittelson & Associates et al. 2013). The types of criteria that transit agencies reported using to evaluate their transit-supportive roadway strategies reflect a balance of these different perspectives. In decreasing order of use, these were: â¢ Potential bus travel time savings/speed improvement, â¢ Potential bus reliability improvement, â¢ Ridership (route and stop levels) and number of buses, â¢ Traffic volumes and level of service, â¢ Safety, â¢ Benefit/cost ratio,
42 A Guidebook on Transit-Supportive Roadway Strategies â¢ Street widths, and â¢ Street functional class and adjacent land use environment (Danaher 2010). 4.3 Problems and Potential Strategies There are many possible causes for bus speed and reliability issues; these can either be external to the transit agency or under its control. Likewise, there are often several possible strategies that can address these issues. This section lists some common sources of speed and reliability issues and provides guidance on strategies to consider to address them. As will be seen, a problem can often be addressed from several different anglesâthrough operational changes on the part of the transit agency, through changes in traffic control, and through physical changes to the roadway. Detailed descriptions of each strategy, including potential constraints on the use of the strategy and other important factors to consider before selecting one, are provided in the toolbox chapters (Chapters 5 through 8). Increasing Ridership Increased ridership is a good problem to have but can also lead to longer dwell times that reduce bus travel times. Increasing the route frequency is one option that helps reduce the num- ber of passengers boarding and alighting at a given stop and the number of standees in the aisle, both of which reduce dwell time, but operating funds may not be available to support an increase in frequency. Other options include changing the way fares are paid, such as encouraging greater use of prepaid fare media or allowing all-door boarding in conjunction with proof of payment (Section 5.4) or using larger buses on the route (Section 5.5) to reduce congestion in the aisle. Route Design Two elements of route design can affect bus speeds. The first is the number of times that buses have to stop to serve bus stops. The second is the number of turns made along the route. Consolidating closely spaced stops (Section 5.2) can be a relatively low-cost method to improve bus speeds without significantly inconveniencing passengers. A survey (Boyle 2013) found that this action was most frequently cited by transit agencies as the âmost successful action takenâ to improve bus speeds. Some turns may have been introduced into a route long ago, but the justification for divert- ing or turning the route at that location may no longer exist. A comprehensive review of route design (Section 5.3) may identify opportunities to streamline a route to reduce delays caused by unnecessary turns or by turning at a location that experiences high delays. A survey (Boyle 2013) found that this strategy was tied for second (with transit signal priority) in being cited by transit agencies as the âmost successful action takenâ to improve bus speeds. Some route diversions may also be necessary because the existing street network does not provide through connections for motor vehicles between locations that would preferably be connected by transit service or require a roundabout routing to serve. In these cases, bus-only links (Section 7.7) that provide such connection for buses while preventing undesired cut-through traffic may be an option. Frequently, though, turns are a necessary evil on a route. In this situation, strategies are avail- able for minimizing the delay experienced by buses when making a turn or when weaving across traffic lanes to access a left-turn lane. At traffic signals, options include any strategy discussed later to reduce traffic signal delay, plus bus-only signal phases (Section 6.9) and pre-signals
Selecting an Appropriate Strategy 43 (Section 6.11). At any type of intersection, allowing buses to make turns that are prohibited to other vehicles for traffic operations or neighborhood traffic management reasons (Section 6.1) can result in a faster, more direct routing. In a transit-supportive policy environment, other potential options at unsignalized intersections may be traffic signal shadowing (Section 6.6) and traffic signals installed specifically for buses (Section 6.12). Delays Leaving Stops On higher-volume streets and at intersections where traffic signals and stop signs create queues of vehicles, buses may experience significant delays finding a gap in traffic to leave the bus stop and proceed along their route. If the bus stop is located in a bus pullout, eliminating, relocating, or consolidating this stop with a nearby bus stop (Sections 5.1 and 5.2) may be an option. If a parking lane is provided along the street, extending the curb into the parking lane at the bus stop (Section 7.5) allows buses to stop in the travel lane and proceed when ready. At traffic signals with right-turn lanes or available width from a parking lane, a queue jump (Section 6.10) can allow buses to re-enter the travel lane ahead of other traffic. Bus lanes (Section 8.1) are a potential option for BRT routes, streets with unused capacity (e.g., one-way streets), and streets with higher volumes of buses. Finally, implementing yield-to-bus laws (Section 6.3) is a potential option. Traffic Signal Delays Traffic signals are both a significant source of bus delay and a significant contributor to bus travel time variability. Fortunately, a number of potential strategies are available to minimize these delays. One challenge in implementing signal-related strategies is that, while these strategies tend to provide greater bus benefits as traffic volumes approach the intersectionâs capacity, intersection operations near capacity also tend to constrain a roadway agencyâs ability to adjust the signal timing or phasing without severely affecting the overall intersection operation. Consequently, these strategies often have the most potential when volumes are relatively high (so a significant bus delay reduction can be achieved) but not when intersections are at or close to capacity (so some flexibility is available to make changes to the signal control). A second potential challenge to be aware of is that traffic signal controllers may need to be upgraded to implement some of the strategies. A low-cost starting point is to identify traffic signals where the existing timing does not appear to work well for buses or general traffic (e.g., where the signal is red but no side-street vehicles or pedestrians are being served) and could benefit from retiming. Some transit agencies have estab- lished formal processes for receiving tips from bus operators about poorly timed signals and passing them along to the appropriate roadway agency to be investigated (Boyle 2013). A more involved approach applying the same principles is to evaluate signal timing in general along a street (Section 6.4), identify potential opportunities to increase green time for the intersection approaches served by buses, reduce the traffic signal cycle length, or improve the progression provided between pairs of signals. These actions can benefit all traffic using the intersection, not just buses. Relocating bus stops from the near side to the far side at intersections (Section 5.1) is an effective, low-cost way to avoid delays caused by right-turning traffic. Phase reservice (Section 6.5) can also be a low-cost option for reducing delays to buses making left turns at an intersection or operating on low-volume side-street approaches. Other available options will require investments in new traffic signal infrastructure and, potentially, infrastructure onboard the bus. TSP (Section 6.7) offers the potential to signifi- cantly reduce traffic signal delays and improve travel time reliability and was frequently cited in a survey as being the âmost successful action takenâ by a transit agency to improve bus speeds (Boyle 2013). However, there have also been a number of documented instances where little or no travel time benefit was obtainedâeither because the schedule was not adjusted to take
44 A Guidebook on Transit-Supportive Roadway Strategies advantage of potential time savings or because the time saved at one intersection was lost at the next intersection (e.g., because although the bus arrived earlier at the next intersection, it was not able to pass through the intersection any sooner). Therefore, it is important to evaluate the potential benefits of TSP implementation as a corridor, rather than intersection by intersection, prior to committing to a significant capital investment. Other signal-related strategies that might be considered in some circumstances are bus-only signal phases (Section 6.9), queue jumps (Section 6.10), and pre-signals (Section 6.11). Congested Roadways Roadways that operate over capacityâwhether because traffic demands exceed a traffic signalâs capacity to serve them or because of physical bottlenecks that reduce the roadwayâs capacityâ are a particular challenge to address. Over-capacity operation manifests itself as long and growing queues of vehicles. It can take several traffic signal cycles for vehicles to get through the signal, or many minutes to get past the point where a roadway narrows. Strategies to address these situations work by managing the queues or providing ways for buses to move around the queues. These include bus shoulder use (Section 7.3), queue bypass lanes (Section 8.6), pre-signals (Section 6.11), and contraflow bus lanes (Section 8.8). Other Traffic-Related Delays Strategies to address traffic delays not associated with traffic signals or exiting bus stops include the following: â¢ Turn restrictions (Section 6.2), where vehicles stopped to make turns (particularly left turns when no left-turn lane is available) delay both buses and general traffic; â¢ Speed hump modifications or removals (Section 7.1) to eliminate bus delays caused when buses must slow well below the posted speed to safely traverse the hump; and â¢ Bus lanes (Section 8.1), which remove some to nearly all of the traffic interference (depending on the bus lane type) experienced by buses traveling in mixed traffic. In addition, standard traffic engineering techniques outside the scope of this guidebook, such as providing turn lanes, can improve traffic flow for both buses and general traffic. Support Strategies Some strategies do not provide a direct travel time or reliability benefit on their own but help make another strategy possible or help another strategies achieve its maximum effectiveness. These include: â¢ Enforcement (Section 6.13), which supports bus lanes and bus-only links by discouraging their use by unauthorized vehicles; â¢ Red-colored pavement (Section 7.4), which supports strategies such as bus lanes, bus-only links, and turn lanes restricted to buses by improving their conspicuity and thereby reducing their use by unauthorized vehicles; â¢ Bus stop lengthening (Section 7.2), which may be required when longer buses are introduced on a route or routes are consolidated on a street on which bus lanes have been implemented; â¢ Boarding islands (Section 7.6), which make bus stops possible along left-side bus lanes, some types of reversible bus lanes, and queue jumps accessed from channelized right-turn lanes; and â¢ Transit signal faces (Section 6.8), which provide special vertical and horizontal bar go and stop indications to buses to avoid potential driver confusion if regular red/green/yellow indications were used.
Selecting an Appropriate Strategy 45 Packages of Strategies Many strategies lend themselves to being implemented in conjunction with other strategies, thereby increasing the overall benefit to transit vehicles. The Companion Strategies sections in the toolbox chapters (Chapters 5 through 8) describe which other strategies work well with a given strategy. 4.4 Evaluating Strategies on a Corridor Basis Most literature on transit-supportive roadway strategiesâincluding this guidebookâpresents bus delay benefits from intersection and other spot treatments on a per-site basis. However, it is important to be aware that the time saved at one location may be lost at the next downstream traffic signal under some circumstances, resulting in no net benefit. This situation could occur, for instance, when transit signal priority gives a green signal 10 s early to the busâs approach, allowing the bus to depart 10 s sooner than it would have otherwise. An evaluation of the effect of signal priority at this intersection would say that it saved the bus 10 s. However, assume that the bus arrives at a near-side stop at the next traffic signal 10 s early, but by the time it is finished serving passengers, the signal has already turned red and the bus has to wait until the next green to continue. In this situation, the bus departs the second intersection at exactly the same time it would have if no signal priority had been provided at the first intersectionâthe delay saved at the first intersection is converted into additional signal delay at the second intersection, and the bus ends up with no net benefit from the strategy in this case. Therefore, when estimating the benefit of a transit-supportive strategy at a given location, it is important to consider whether the next downstream signal will negate the effect of the strat- egy. The likelihood that this will happen depends on the relative timing of the two signals (i.e., when the second signal turns green relative to the first), the time required for a bus to travel between the two signals, bus dwell time (and dwell time variability) accumulated between the signals, and the amount of green time provided. Appendix C of the TCRP Project A-39 final report (TCRP Web-Only Document 66), building on work by St. Jacques and Levinson (1997), describes an analytical method for estimating the likelihood that a bus will be able to make the green light at a downstream signal and thus preserve the delay benefit provided by a strategy implemented upstream. 4.5 Strategy Selection Matrix Table 5 presents a summary of key benefits, costs, and issues associated with each of the transit-supportive strategies described in this guidebook. It also presents a brief description of one or two common applications for each strategy. The table can be used as a quick reference for identifying potential strategies applicable to a particular situation. The reader can then turn to the corresponding strategy description in the strategy toolbox (Chapters 5 through 8) for detailed information and guidance. Bold type in the table indicates typical uses or outcomes out of the wider range given in the table. Table 5 provides the following information: â¢ Typical application. One or two typical situations when the strategy might be applied. The Applications sections in the strategy toolbox provide more comprehensive listings of applications. â¢ Traffic volumes. Typical traffic conditions under which the strategy is most applicable: low = volume-to-capacity (v/c) ratios < 0.5, moderate = v/c ratios of 0.5 to 0.8, high = v/c ratios
46 A Guidebook on Transit-Supportive Roadway Strategies Strategy and Secon Number Typical Applicaon Traffic Volumes Bus Volumes Bus Speed Bus Reliability Auto Speed Planning Costs Capital Costs Other Issues BUS OPERATIONS STRATEGIES Relocate stop (5.1) Near-side stop L to H Any + to ++ + + L L to M 1,2 Consolidate stops (5.2) Short stop spacing Any Any ++ to +++ 0 to + 0 to + M to H L 2,3 Route design (5.3) Route deviaÂons Any Any ++++ 0 to + 0 M to H L 2,4 Fare payment (5.4) Long dwell Âmes Any Any + to +++ 0 to + 0 to + M to H M to H 4,5 Vehicle changes (5.5) Long dwell mes Any Any + to ++ 0 to + 0 to + L H 3,6,7 TRAFFIC CONTROL STRATEGIES Movement restricon exempon (6.1) Turns in route L/M to H Any +++ to ++++ 0 to + - to 0 M L to M 8 Turn restricons (6.2) Delays from turning cars Any Any + to +++ + - to + M L 8,9 Yield to bus (6.3) Offline bus stops Any Any 0 to ++ 0 to + - M to H L to H 10 Passive signal Âming adjustments (6.4) Signals L to M Any 0 to ++ 0 to + - to + M None 11 Phase reservice (6.5) Bus turns at signal L to M Any ++ to +++ + - to + L to M 0 to M 9,12 Traffic signal shadowing (6.6) Bus turning delay at unsignalized int. M to H L ++ to +++ 0 to + - M M 13 Signal priority (6.7) Signals M to H L to M 0 to ++ ++ - to + M to H H 9,10,12 Transit signal faces (6.8) Signals Any Any 0 0 0 L to M M 10,14 Bus-only phase (6.9) Unusual bus move L to H Any ++ to +++ 0 to + - L to M 0 to M 10,12,14 Queue jumps (6.10) Signals M to H L to M + to ++ 0 to + - L to M M to H 10,12,15 Pre-signals (6.11) Bus lane end M to VH M to H + to +++ + - to 0 M M to H 1,11,14 Bus traffic signal (6.12) Turn at unsignalized int. M to H M to H +++ + - M-H H 8,11,16 Enforcement (6.13) Fares, traffic control Any Any 0 to +++ 0 to + 0 H 0 14,17 Enforcement (photo/video) (6.13) Bus lanes, bus-only links Any Any 0 to +++ 0 to + 0 H H 10,14,17 INFRASTRUCTURE STRATEGIES Modify speed hump (7.1) Speed humps Any Any + to ++ 0 0 to + M L to M 5,7,8 Lengthen bus stop (7.2) Short bus stops Any M to VH 0 to ++++ + 0 to + L L to M 1,3 Bus shoulder use (7.3) Suburban arterials VH L to H ++++ ++ 0 H M to H 5,8,9,10,20 Red pavement (7.4) Bus lanes Any Any 0 0 0 M to H M to H 14,16 Curb extensions (7.5) Low-speed urban streets with peds L to M L to M + to ++ + - to + L to M M 2,18,19 Boarding islands (7.6) Non-curb bus stops Any Any 0 0 0 L to M L to H 2,14 Bus-only links (7.7) Subdivisions, urban centers 0 L to H ++++ 0 to + 0 L to M L to M 5 BUS LANE STRATEGIES Bus lanes, generally (8.1) BRT, high bus volumes M to H L/M to H ++ to +++ + - to 0 H L to H 5,9 Curbside (8.2) Preserve travel lanes Same L/M to H/VH 0 to +++ 0 to + Same Same Same 1 Shared bus/bike (8.3) ROW constraints Same L to M Same 0 to + Same Same Same 1,21 Interior (8.4) Preserve parking Same Same Same Same Same Same Same LeÂ-side (8.5) Right-side traffic congesÂ on Same Same Same Same Same Same Same 2 Queue bypass (8.6) BoÂleneck H to VH Same ++++ Same 0 Same Same 21 Median (8.7) Minimize traffic interference Same Same Same Same Same Same Same 2 Contraflow (8.8) Strong direcÂ onal flow H to VH Same ++++ Same Same Same Same 2,8 Reversible (8.9) ROW constraints M to VH Same Same Same Same Same Same 2,8,21 Notes: 0 = none, L = low, M = moderate, H = high, VH = very high. Int. = intersection, âSameâ = same as for bus lanes generally. Bold type indicates typical situations. See Table 6 for the âOther Issuesâ notes. Table 5. Strategy selection matrix.
Selecting an Appropriate Strategy 47 of 0.8 to 1.0, and very high = v/c ratios > 1.0, considering the potential magnitude of bus delay savings and the strategyâs flexibility to accommodate high-volume situations. â¢ Bus volumes. Typical bus volumes under which the strategy is most applicable: low = <10 buses per hour per direction, moderate = 10 to 30 buses per hour, high = 31 to 100 buses per hour, and very high = >100 buses per hour. Under favorable policy environments, lower bus volumes than indicated may be appropriate. â¢ Bus speed. Typical bus delay benefit, on a per-site or per-block basis: 0 = no effect, + = <5 s, ++ = 5 to 15 s, +++ = 16 to 60 s, and ++++ = >60 s. The Benefits sections in the strategy toolbox provide quantitative data. â¢ Bus reliability. Relative impact on bus travel time variability: 0 = no effect, + = positive impact, and ++ = larger positive impact relative to other strategies. The Benefits sections in the strategy toolbox provide additional qualitative and quantitative information. â¢ Automobile speeds. Relative impact on automobile travel times: - = worsens automobile travel times, 0 = no effect, and + = improves automobile travel times. The Benefits and Cost Considerations sections in the strategy toolbox provide additional information, depending on whether the impact is positive or negative. â¢ Planning costs. Effort required for planning, analysis, and stakeholder coordination, rela- tive to other strategies: low, moderate, high. The Cost Considerations sections in the strategy toolbox provide additional information. â¢ Capital costs. Typical capital costs on a per-site or per-block basis: 0 = none, low = <$10,000, moderate = $10,000 to $100,000, high = >$100,000. The Cost Considerations sections in the toolbox provide additional information, as well as information on strategy impacts on main- tenance and bus operations costs not shown in the table. â¢ Other issues. Other important issues to consider when evaluating the strategy. This list is not comprehensive; see the Constraints and Implementation Guidance sections in the strategy toolbox for potential additional issues that may need considering in some circumstances, along with Appendix C on managing bus and bicycle interactions at bus stops. The numbers in the âOther Issuesâ column in Table 5 are explained in Table 6. (1) curb space usage by others (2) passenger access to stops, ADA consideraons (3) bus stop/bus lane capacity (4) spot treatment or system-wide applicaon (5) enforcement (6) maintenance facility upgrades, staff training (7) passenger quality of service (8) safety (9) part-me or condional operaon feasible (10) changes to traffic laws or design standards (11) traffic signal coordinaon (12) signal controller capability (13) alternave strategies more desirable if feasible (14) support strategy that allows other strategies (15) bus ability to access bus lane (16) FHWA experimentaon request needed (17) may add to transit agency operang costs (18) motor vehicle ability to pass stopped buses (19) bus dwell time (20) shoulder width and pavement strength (21) ROW availability to work beÂer Table 6. âOther Issuesâ notes for the Table 5 strategy selection matrix.