The history of bus infrastructure in the U.S. is intertwined with the development of high-occupancy vehicle (HOV) lanes. The 1970s inaugurated an era of vigorous development of busways and other HOV facilities. Exclusive busways or bus lanes were implemented on the Shirley Highway in the Washington, D.C. area, the El Monte Freeway in Los Angeles, the I-495 approach to the Lincoln Tunnel in New Jersey, California Highway 101 in the San Francisco metropolitan area, and a separate right-of-way in Pittsburgh. At the same time, HOV lanes open not only to buses, but also to vanpools and carpools, were being created on highways serving New York, Los Angeles, Seattle, San Francisco, Washington, D.C., and Honolulu.
Contraflow HOV lane with buses and carpools.
With the exception of the I-495 lane in New Jersey and the Pittsburgh busway, the early highway exclusive bus lanes have all since been converted to HOV lanes, with carpools being the predominant users. During the 1980s, the number of freeway HOV route miles increased by over 100 percent, although there are several examples of highways -- such as the Santa Monica Freeway in Los Angeles and the Garden State Parkway in New Jersey -- where HOV lanes were discontinued due to insufficient usage or other problems, such as public opposition, which led to a court decision terminating the Santa Monica Freeway HOV treatment. There are now over 80 HOV facilities greater than 3.5 miles in length throughout the U.S.
At the same time that HOV and exclusive bus facilities were being implemented on the nation’s highways, bus lanes and transit malls were introduced in the downtown areas of many cities. The most prominent examples include the Nicollet Mall in Minneapolis, the Portland Transit Mall in Portland, Oregon, and the 16th Street Mall in Denver, all of which are still in operation. Bus lanes were introduced on New York City’s Madison Avenue on May 26, 1981, reducing bus travel times by 34 to 42 percent and increasing ridership by 10 percent. Some downtown and arterial bus lane projects implemented in the 1970s and 1980s have been discontinued or cut back, however, and there are only a few cases in which infrastructure investments have been integrated into a high quality bus transit network.
The premier examples of high quality bus transit facilities in the U.S. are in Pittsburgh, Seattle, and Miami. The Port Authority of Allegheny County operates two 2-lane busways in the Pittsburgh metropolitan area: the 7-mile East Busway, which shares right-of-way with light rail transit, and the 4-mile South Busway. A 5-mile Airport Busway currently is under construction. These facilities serve express buses traveling to the downtown area, where several bus lanes operating on city streets expedite local access and distribution. The opening of the East Busway in 1983 reduced travel times by 15 to 23 percent on the various bus routes served. In Seattle, a regional network of freeway HOV lanes connects buses to a core of underground tunnels in the city center, where grade separation allows buses to operate in a rapid transit mode, bypassing traffic congestion on surface streets. The 8.2-mile South Dade Busway opened on February 3, 1997, connecting to the southernmost stops on Miami’s Metrorail. The 2-lane busway, which parallels U.S. Route 1, is served by 16 stations. Eleven bus routes serving Dade County now operate on or feed the busway.
Extensive development of HOV lanes throughout the U.S. represents a significant effort -- illustrated most clearly in the case of busways -- to improve bus service on the highways connecting suburban and downtown areas. Providing high quality service within the downtown sections of metropolitan areas is key to the Bus Rapid Transit concept, however, and has not been the subject of a comparable effort. While busways and freeway HOV facilities can substantially reduce travel times and improve service, mobility within congested urban centers is essential to support the economic and social functions of cities and to sustain high levels of transit ridership.
In most cities, a number of factors impede the upgrading of right-of-way to provide for exclusive bus lanes on arterial and local city streets. The most basic obstacle to creating a bus lane on a city street is the lack of an adequate cross section to separate buses from general-purpose traffic. At a minimum, bus lanes require an 11-foot cross section per direction. On most major two-way streets, the creation of even a single direction, reversible bus lane will limit at least one direction of general-purpose traffic to a single lane, likely producing serious adverse consequences for general-purpose traffic. There may be more opportunities to dedicate a lane for exclusive bus use on relatively wide one-way streets, although in many cases this too will produce adverse effects on general-purpose traffic flows and losses of scarce on-street parking spaces.
Depending on whether a bus lane is located along the curb or in the median of a two-way street, conflicts are created with right- or left-turning vehicles. The need to allow general-purpose traffic to use a bus lane for turning interferes with bus operations, causing substantial increases in travel time and adding to the problems of enforcing the restriction of the lane to buses under all other circumstances. Curbside parking by delivery and service vehicles also obstructs bus movement and is particularly problematic if the bus lane is restricted to only a single lane width. Dual-width bus lanes are markedly superior to single-width lanes, but obviously require a substantially wider cross section, which typically is not available. In the case of a median lane, another drawback is that passengers must walk across general-purpose traffic lanes to reach the bus stop.
As a practical matter, traffic signal priority or preemption can be implemented effectively only in conjunction with dedicated bus lanes, streets, or where geometry allows, queue bypass lane segments that allow buses to circumvent traffic at an intersection approach. A major limitation on bus signal preference is the adverse effect associated with the reduction of green signal time for general-purpose traffic on the cross streets. Moreover, the constraints imposed by traffic signal progression will limit the effective application of signal preemption in many urban arterial street networks.
From the standpoint of bus service quality, there is a trade-off between the improvement in travel times that can be achieved by reducing the number of stops, as in the case of rapid rail service, versus the convenient access made possible by frequent stops, as in conventional bus service. A number of inherent difficulties also affect efforts to reduce boarding times. An innovation that promises to speed the time required for payment of fares is the use of "smart" card electronic systems. Nevertheless, this improvement will not eliminate the need to restrict boarding to the front door of the bus.
One potential option for alleviating this and other physical constraints on boarding would be greater use of enclosed bus waiting areas or stations where passengers would be required to enter the waiting areas in advance, thus allowing boarding through all doors of the bus. Enclosed boarding areas take up significant sidewalk space, however, which may not be available in many locations. Moreover, capital, operating, and maintenance costs are likely to limit the number of such facilities that can be provided, even in areas where spatial constraints are not a significant problem. Thus, if the convenience of frequent stops is to be maintained, conventional boarding procedures would continue at many or most locations.
System integration is an issue arising from the need to provide for transfers between routes where passengers pay fares upon entering boarding areas and routes with on board payment. Another potential concern is that specialized vehicle boarding features designed to be compatible with platforms in enclosed areas may impose constraints on the deployment of a transit system’s vehicle fleet.
Several U.S. and Canadian cities have introduced or are in the process of implementing elements of Bus Rapid Transit, as illustrated in the following examples.