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60 CHAPTER SIX WARRANTS, COSTS, AND IMPACTS OF TRANSIT PREFERENTIAL TREATMENTS This chapter presents information on the warrants, costs, Exclusive Transit Lanes and impacts of different transit preferential treatments, where information is available on these subjects. The information Exclusive transit lanes outside of median facilities within is derived from a review of information in the documents eval- the street ROW require (1) a sufficient frequency of transit uated in the literature review for this report, and insights from service, (2) traffic congestion along the roadway, (3) suitable the transit and traffic agency web surveys and case studies con- street geometry, and (4) community willingness to enforce the regulations. From a premium transit perspective, transit ducted. Primary documents with useful information include lanes are useful in establishing a clear identity for such ser- TCRP Report 100: Transit Capacity and Quality of Service vice within the street ROW. Guidelines for the operation of Manual, 2nd Edition (3), Highway Capacity Manual 2000 exclusive transit lanes on urban streets include the following, (19), TCRP Report 118: Bus Rapid Transit Practitioner's separated by bus versus LRT/streetcar operations (5). Guide (5), TCRP Report 90: Bus Rapid Transit, Volume 2: Implementation Guidelines (4), and NCHRP Report 155-- Bus Use of Highways: Planning and Design Guidelines (2). Bus This chapter also reviews the applicability of different ana- 1. Concurrent-flow lanes may operate along the outside lytical tools to assess the impacts of different transit preferen- curb, in the lane adjacent to a parking lane (interior tial treatments on transit and traffic operations. lane) or in a paved median area (without a dedicated median transitway). 2. Concurrent-flow lanes can operate at all times, for WARRANTS AND CONDITIONS extended hours (e.g., from 7 a.m. to 7 p.m.), or just dur- FOR APPLICATION ing peak hours. 3. Contraflow lanes should operate at all times. Median Transitways 4. Under conditions of heavy bus volumes, dual con- Exclusive median facilities or transit malls are typically applied current-flow or contraflow lanes may be desirable. for LRT operations on urban streets owing to the length of 5. Where the bus lanes operate at all times, special col- ored pavement may be desirable to improve the iden- the trains (and hence potential substantial impact to local tity of the BRT operations. access if operated curbside) and the need to preserve some 6. Bus lanes should be at least 11 ft wide to accommodate operating speed advantages for such a mode. For streetcars an 8.5-ft bus width. and buses, impetus for operation in a median transitway 7. The bus lanes should carry as many people as in the is a greater number of vehicles (thus to reduce conflicts adjacent general traffic lane. Generally, at least 25 buses with general traffic) and again a desire for higher operating should use the lanes during the peak hour. (Ideally, there speeds. should be at least one bus per signal cycle to give buses a steady presence in the bus lane.) There should be at Wider arterial streets are needed to implement median least two lanes available for general traffic in the same transitways. Sufficient ROWs must exist to provide for direction, wherever possible. adequate transit station platforms (whether near side or far 8. Parking should be prohibited where bus lanes are along side) and the provision for near-side left-turn lanes at sig- the curb, but it may remain where interior bus lanes are nalized intersections. If a median busway is used by more provided. (Interior bus lanes are located in the lanes than one route, then building in passing lanes may be desir- adjacent to the curb lanes.) able in station areas. 9. There should be suitable provisions for goods delivery and service vehicle access, either during off-hours or In NCHRP Report 155 (2), warrants for "median bus off-street. lanes" were defined as ranging from 60 to 90 one-way buses per peak hour, with a minimum daily bus volume of 600. The In NCHRP Report 155 (2), volume warrants for both concur- bus volumes were correlated to a one-way bus passenger vol- rent-flow and contraflow curb bus lanes were identified. ume of 2,400 to 3,600 per peak hour. Table 17 identifies the peak hour and daily bus volumes and
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61 TABLE 17 VOLUME WARRANTS FOR CURB BUS LANES Range in One-Way Peak-Hour Volume Minimum Daily Bus Curb Bus Lane Volume Bus Passengers Concurrent flow In CBD 200 2030 8001,200 Outside CBD 300 3040 1,2001,600 Contraflow Short segment 200 2030 8001,200 Extended segment 400 4060 1,6002,400 Source: NCHRP Report 155, Table 43 (2). CBD = central business district. assumed bus passengers associated with different treatments veys of existing conditions or through simulation modeling of in downtown areas versus outside of downtown areas. future conditions. Studies have found that TSP is most effec- tive at signalized intersections operating within LOS "D" and "E" conditions with a volume-to-capacity ratio (v/c) between LRT/Streetcar 0.80 and 1.00. There is limited benefit in implementing prior- ity under LOS "A" through "C" conditions as the roadway 1. It is important that LRT/streetcar lanes operate in the is relatively uncongested and neither major bus travel time same direction as parallel general traffic (contraflow or reliability improvements can be achieved. Under oversatu- lanes are discouraged); rated traffic conditions (v/c greater than 1.00), long vehicle 2. That any dedicated LRT/streetcar lanes operate at all queues prevent transit vehicles from getting to the intersection times; soon enough to take advantage of TSP without disrupting gen- 3. That LRT/streetcar lanes have a more substantial ele- ment to separate operations from general traffic, such as eral traffic operations. low-profile pavement bars, rumble strips, contrasting pavement texture, or mountable curbs, than just paint or A basic guideline is to apply TSP when there is an esti- striping; and mated reduction in transit vehicle delay with negligible change 4. Separate LRT signals clearly distinguishable from traf- in general traffic delay. Given this condition, the net total per- fic signals in design and placement be provided. son delay (on both buses or trains and general traffic) should decrease with application of TSP at a particular intersection or The primary basis for determining whether lane dedication along an extended corridor. is applicable typically involves a comparison of costs and ben- efits. In this case, the mixed-traffic operating scenario would Given the frequency of transit service in a given corridor, be compared with a dedicated running way scenario. Effec- TSP may only be given to certain transit vehicles such that the tiveness can then be analyzed in terms of changes in total disruption to general traffic operations is minimized. Condi- person travel time for all travelers in the given corridor irre- tional priority is most commonly accepted as an initial TSP spective of mode. The analysis can take into account potential application for bus operations in a corridor, assuming that shifts by motorists to parallel arterials if capacity is taken away buses would be issued priority only if they are behind sched- from general traffic on the arterial in question. ule or have a certain number of persons on board the bus. Los Angeles Metro Rapid, for example, limits TSP to every other The most critical parameters affecting the results of any signal cycle. evaluation of dedicated bus lanes are the number of buses in the peak hour and peak direction and the number of people on TSP has been found to be most effective with transit stops the buses. Travel time savings for current transit users and the located on the far side of signalized intersections so that a bus, potential attraction of new riders, along with potential operat- streetcar, or train activates the priority call and travels through ing and maintenance cost savings, is traded off against changes the intersection and then makes a stop. Past studies and actual in travel times for current general traffic, access, and parking applications have shown that greater reduction in transit travel impacts at adjacent land uses. time and variability in travel times can be achieved with a far- side versus near-side stop configuration. Transit Signal Priority Curb Extensions TSP is typically applied when there is significant traffic con- gestion and, hence, transit delays along a roadway. Estimated Curb extensions are typically warranted when there are dif- bus travel time and delay can be identified through field sur- ficulties for buses trying to reenter the traffic stream, usually