Issues In Bus Rapid Transit (PDF)
(427 KB) (Requires Adobe Acrobat Reader, available for free).
Bus systems provide a versatile form of public transportation with the flexibility to serve a variety of access needs and an unlimited range of locations throughout a metropolitan area. Because buses travel on urban roadways, infrastructure investments needed to support bus service can be substantially lower than the capital costs required for rail systems. As a result, bus service can be implemented cost-effectively on routes where ridership may not be sufficient or where the capital investment may not be available to implement rail systems.
Traffic congestion, urban sprawl, central city decline, and air pollution are all problems associated with excessive dependence on automobiles. Increasing recognition of the need for high-quality transit service to alleviate these conditions has fueled growing demand for new rail services throughout the United States (U.S.). Rail systems have in fact played an essential role in preserving and revitalizing the downtown areas of major American cities, ranging from New York to San Francisco and Washington, D.C. In these and numerous other cities, however, buses also provide an attractive and effective alternative to automobiles, reaching into central cities, local neighborhoods, and the suburbs to meet the mobility needs of millions of people.
A double-articulated bus on one of Curitiba's exclusive bus lanes.
Despite the inherent advantages of bus service in terms of flexibility and low capital cost, the traveling public frequently finds the quality of bus service provided in urban centers to be wanting. Conventional urban bus operations often are characterized by sluggish vehicles inching their way through congested streets, delayed not only by other vehicles and traffic signals, but also by frequent and time-consuming stops to pick up and discharge passengers. Buses travel on average at only around 60 percent of the speeds of automobiles and other private vehicles using the same streets due to the cumulative effects of traffic congestion, traffic signals, and passenger boarding. Moreover, compared to rail systems, the advantageous flexibility and decentralization of bus operations also result in a lack of system visibility and permanence that contributes to public perceptions of unreliability and disorganization.
1.1 What is Bus Rapid Transit?
Low-cost investments in infrastructure, equipment, operational improvements, and technology can provide the foundation for Bus Rapid Transit systems that substantially upgrade bus system performance. Conceived as an integrated, well-defined system, Bus Rapid Transit would provide for significantly faster operating speeds, greater service reliability, and increased convenience, matching the quality of rail transit when implemented in appropriate settings. Improved bus service would give priority treatment to buses on urban roadways and would be expected to include some or all of the following features:
- Bus lanes: A lane on an urban arterial or city street is reserved for the exclusive or near-exclusive use of buses.
- Bus streets and busways: A bus street or transit mall can be created in an urban center by dedicating all lanes of a city street to the exclusive use of buses.
- Bus signal preference and preemption: Preferential treatment of buses at intersections can involve the extension of green time or actuation of the green light at signalized intersections upon detection of an approaching bus. Intersection priority can be particularly helpful when implemented in conjunction with bus lanes or streets, because general-purpose traffic does not intervene between buses and traffic signals.
- Traffic management improvements: Low-cost infrastructure elements that can increase the speed and reliability of bus service include bus turnouts, bus boarding islands, and curb realignments.
- Faster boarding: Conventional on board collection of fares slows the boarding process, particularly when a variety of fares is collected for different destinations and/or classes of passengers. An alternative would be the collection of fares upon entering an enclosed bus station or shelter area prior to bus arrivals. This system would allow passengers to board through all doors of a stopped bus. A self-service or "proof-of-payment" system also would allow for boarding through all doors, but poses significant enforcement challenges. Prepaid "smart" cards providing for automated fare collection would speed fare transactions, but would require that boarding remain restricted to the front door of the bus.
Changes in bus or platform design that could provide for level boarding through the use of low-floor buses, raised platforms, or some combination thereof could make boarding both faster and easier for all passengers.
- Integration of transit development with land use policy: Bus Rapid Transit and compact, pedestrian-oriented land use development are mutually supportive. The clustering of development has the additional benefit of conserving land and promoting the vitality of neighborhoods and urban commercial centers. Bus Rapid Transit can be most effective when integrated within a broader planning framework encompassing land use policies, zoning regulations, and economic and community development.
- Improved facilities and amenities: The operational and travel time benefits resulting from the separation of buses from general-purpose traffic can be augmented with improved amenities such as bus shelters and stations. These facilities provide protection from the elements and can also be equipped to furnish information such as printed routes and schedules or electronically transmitted real time schedule data. Space can also be leased to commercial convenience services.
1.2 Reducing Delay: The Key to Bus Rapid Transit
Bus operations on a typical urban or suburban arterial are subject to several types of delay that reduce bus operating speed to generally only 60 percent of that of other vehicles. Figure 1 is from Transit Cooperative Research Program Report 26, Operational Analysis of Bus Lanes on Arterials. This figure summarizes and graphically displays the several components of bus travel time such as moving, passenger stops, and traffic delay, which consists of traffic signal delay, right turn delay and general congestion delay. Figure 1 also shows how certain types of delay such as congestion delay and passenger stop delay are proportionately greater in more congested areas.
The essence of Bus Rapid Transit is that bus operating speed and reliability on arterial streets can be improved by reducing or eliminating the various types of delay. A discussion of each travel time component and methods for reducing delay follows:
- Uncongested moving or free flow operating time This component can only be reduced if speed limits are raised.
- Delay due to general congestion This component can be reduced if general congestion is reduced and/or if buses are given preferential treatment through creation of a reserved lane. Policies requiring general-purpose traffic to yield to buses re-entering the traffic stream from bus stops could also reduce delays associated with general congestion.
- Delay due to traffic signals Priority treatment of buses at intersections holds the potential to reduce a significant source of delay in bus operations. Today’s traffic signal control systems are tightly interconnected, however, in order to provide progression of general traffic through urban grid networks. Therefore, bus signal priority treatments would have to be constrained to modest variations within the context of maintenance of progression. Bus operating speeds may also improve if traffic signal cycles are coordinated to the time required for passenger service, i.e., the red phase occurs during the time needed for passenger boarding and fare collection.
- Delay due to right turns This type of delay occurs when buses are traveling in the curb lane and a queue of right-turning vehicles blocks the bus from moving forward. This delay may be overcome by relocating bus stops to the far side of the intersection so the bus may be able to bypass the right turning queue in the lane next to the curb lane. Alternately, right turns may be prohibited as they were on Madison Avenue (with two exclusive bus lanes between 45th and 59th Streets) in New York City, significantly reducing bus travel times. This solution, however, may not be viable everywhere.
- Delay due to passenger stops This includes passenger boarding time, collection of fares, etc. Boarding time can be reduced by improvement of the fare collection process, e.g. pre-payment of fares, self-service fare collection (honor system), greater use of passes, smart cards, etc. and by easing the boarding process with low-floor buses together with high platforms so that wheelchair-bound passengers could roll on without lifts. This component can also be reduced if stop spacing is increased and the number of stops are reduced. There is a trade-off between stop spacing and convenience to passengers.