Click for next page ( 6


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 5
5 CHAPTER TWO TYPES OF TRANSIT PREFERENTIAL TREATMENTS OVERVIEW ways with the transit corridor are typically converted to right- in, right-out operation. Transitways interface with general There are several different types of transit preferential treat- traffic at signalized intersections, where cross streets remain ments that can be applied on urban streets. These can be divided and both left turns on the street the transitway is operating into treatments applied over a given roadway segment or at a on and cross street traffic typically is accommodated at-grade. specific location (typically at an intersection). Two basic types To accommodate left turns and U-turns for general traffic on of treatments have been identified, three related to roadway the transitway street, dedicated left-turn lanes are provided to segments and four to spot locations. allow protected left-turn phasing to be provided, given the median separation and presence of the transitway. Roadway Segments Median transitways typically have stations at signalized Median transitways, intersections, where pedestrians can access the station plat- Exclusive transit lanes outside a median area (concurrent- forms using crosswalks and pedestrian signal phasing. flow, contraflow, bi-directional, intermittent lanes), Generally, far-side stations are provided to facilitate the pro- and vision of signal priority for transit vehicles. Typically, side Stop modifications (limited stop spacing/stop platforms have been applied for median busways and street- consolidation). car lines because of right side running and doors on the right side of the vehicle. However, there have been some recent Spot Locations (Intersections) applications (in Cleveland and EugeneSpringfield, Oregon) of single center platforms and left side doors (doors on both TSP, sides of a bus). Special signal phasing, Queue jump and bypass lanes, and Because of the typical limited width of median areas and Curb extensions. the overall roadway ROW, most median busways do not incorporate passing lanes, with added width only provided The extent of the preferential treatment (e.g., longer length for stations. of exclusive transit lane or more green time for signal priority), along with traffic conditions along the roadway, will deter- Examples of a median transitway for LRT operations in mine the impact on both transit and traffic operations. Treat- Phoenix are shown in Figure 1, and the former bus median ments can be applied at isolated locations where there is a transitway in Richmond, British Columbia, in Figure 2 particularly high delay to transit vehicles or as a series of treat- (Richmond's busway was recently replaced by an aerial rail ments strung together in a corridor of some length to have a rapid transit line). greater impact on travel time savings and improved reliability. To keep general traffic and pedestrians out of a median This chapter presents the basic characteristics of the differ- transitway, some physical separation between the transitway ent transit preferential treatments addressed in this report. and the adjacent general traffic lanes is provided, ranging from the use of jersey barriers and raised pavement markers, where limited ROW exists, to wider landscaped median treat- MEDIAN TRANSITWAYS ments where more space is available. Added signing at inter- sections designating "Do Not Enter" and "Pedestrians/ Median transitways are exclusive transit facilities developed Bicycles Prohibited" are typically provided. in the median of an urban street. Most applications in North America to date have been associated with light rail transit (LRT) lines, although there are a few median busways emerg- EXCLUSIVE TRANSIT LANES ing. These facilities typically have one lane in each direction, with a dedicated right-of-way (ROW) for the running way Exclusive lanes used by transit on urban streets include new and stations. With the development of median transitways, lanes developed along a roadway through widening or dedica- minor unsignalized street intersections and local access drive- tion of one or more existing general traffic or parking lanes for

OCR for page 5
6 on-street parking and having transit vehicles operate in the parking lane, (2) using a general traffic lane if there is no park- ing, or (3) using the general traffic lane outside (or left) of a parking lane. With this treatment, right-turn and local access driveway traffic are allowed to use the lane over short distances. In some cases, such as in Toronto and Vancouver, carpools and vanpools are allowed to use exclusive bus lanes as a through route as a high-occupancy vehicle (HOV) lane. In a few cases, such as on Madison Avenue in New York City, dual concurrent-flow bus lanes are included to provide added capacity and bus bypass capability. FIGURE 1 Median LRT transitway in Phoenix, Arizona Concurrent-flow lanes can be developed in different oper- (Source: Valley Metro Rail). ating configurations: A lane in each direction of travel operating at the same transit use. These lanes can be designated for transit use dur- time over a designated time period; ing peak periods only, or all day. These lanes typically allow A single lane operating in the peak traffic direction dur- use by general traffic, for left- or right-turn movements, and ing one peak period, with a lane developed in the oppo- local access driveway in and out movements. Most exclusive site direction during the opposite peak traffic period; and lane treatments are used by buses and streetcars, given that A single lane operating in one direction during one time these vehicles better mix with general traffic and the vehicle period, then reversed to operate in the opposite direc- lengths are relatively short, thus not blocking local access tion during another time period (also referred to as a driveways. There are four kinds of exclusive lanes: reversible lane). Concurrent-flow, The most common form of a concurrent-flow transit Contraflow, lane is one located at the right side of the street, adjacent to Bi-directional, and the curb or the shoulder. Although this layout is common Intermittent. throughout North America, simply installing a curbside tran- sit lane does not imply the creation of an exclusive transitway, because curb transit lanes are subject to a variety of interfer- Concurrent-Flow Lane ence and conflicts, including right-turning vehicles, vehicles seeking to park or load at the curb, and vehicles entering or A concurrent-flow lane is a designated lane for transit vehicles exiting at local driveways. In this context, maintaining the moving in the same direction as general traffic. This lane is typ- integrity of the transit lane through signs, markings, educa- ically developed on the right side, adjacent to the curb or shoul- tion, and ongoing enforcement is critical to ensuring the speed der. The lane is typically developed either by (1) removing and reliability of bus service in these lanes. A variation of the curb transit lane that addresses some of these conflicts is an "interior" or "offset" bus lane, which operates in the lane adjacent to the curb lane. This configura- tion leaves the curb lane available for other uses, including direct curb access for loading and parking and right-turn lanes. The negative aspect of an interior or "offset" transit lane is that it has a significant impact on the travel capacity of the street, whereas the installation of a curb bus lane on a street by replacing on-street parking will not change capac- ity. However, in some locations there may be less concern about eliminating roadway capacity, particularly if there are good alternative routes, as compared with eliminating park- ing or loading that may have a greater impact on the viability of local businesses. Figure 3 illustrates concurrent-flow bus lanes in operation FIGURE 2 Former median bus transitway in Richmond, British in Boston, London, and New York. Figure 4 shows similar Columbia (Source: Alan Danaher). lanes for streetcars in Portland (Oregon) and Toronto.

OCR for page 5
(a) (b) (c) FIGURE 3 Exclusive concurrent-flow bus lane applications: (a) Washington Street, Boston, Massachusetts (offset bus lane) [Source: APTA BRT Guideways Guidelines (6)]; (b) London, United Kingdom (curb bus lane) [Source: APTA BRT Guideways Guidelines (6)]; (c) Madison Avenue, New York City (dual bus lanes) [Source: TCRP Report 118 (5 )]. (a) (b) FIGURE 4 Alternate streetcar running way configurations: (a) Portland, Oregon--one-way shared with traffic; (b) Toronto--two-way shared with traffic (Source: www.lightrail.com).

OCR for page 5
8 the green signal to pass though the section in the other direc- tion. This strategy is used when there is only enough room to install a single transit lane of restricted length to traverse through no more than two to three signalized intersections, and with longer service headways. It is noted that the signal system needs to have safeguards that "block out" the sec- tion so that only one transit vehicle can be in the section at a time. It is worth noting that when comparing the operations of a bi-directional lane with a transit vehicle traversing the section in question in mixed-use lanes, the bi-directional lane exclusivity can provide some level of reliability over a con- gested mixed-traffic scenario. Figure 7 provides an example of a bi-directional lane applied on the EugeneSpringfield, Oregon, BRT line. FIGURE 5 Contraflow bus lane on 4th Street, St. Petersburg, Florida (Source: Kittelson & Associates, Inc.). Intermittent Lane An intermittent bus lane or IBL, which can also be called a Contraflow Lane moving bus lane, is a restricted lane for short time duration only. This concept consists of using the general-purpose lane Contraflow transit lanes involve designating a lane for exclu- that can be changed to a bus-only lane only for the time needed sive transit use in the direction opposite that of general for the bus to pass, after which the lane reverts back to a traffic. Contraflow lanes are applied almost exclusively on general-purpose lane until another approaching bus needs the one-way streets, with bus lanes typically being no more than lane for its movement. one to two blocks in length, with longer segments for LRT. With longer segments, lane use control signals need to be applied to properly alert general traffic and transit operators of the direction of use of the lane. Figure 5 illustrates a bus contraflow lane in downtown St. Petersburg, Florida, and Figure 6 illustrates a contraflow LRT lane in downtown Denver. Bi-Directional Lane A bi-directional transit lane is an exclusive lane that allows a transit vehicle (typically a bus or streetcar) to pass in one direction through a constrained section while a transit vehicle waits or dwells at a station or bypass area until it can be given FIGURE 6 Downtown Denver LRT operation in curb lane (southbound on Stout Street) (Source: Denver Regional FIGURE 7 Bi-directional bus lane--EugeneSpringfield, Transportation District). Oregon, BRT (Source: Lane Transit District)