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This article is about high-capacity bus transit systems. For lower-capacity transit systems, see share taxi and bus; for rail transit systems see tram, light rail and rapid transit.
Bus rapid transit (BRT) is a broad term given to a variety of transportation systems that, through improvements to infrastructure, vehicles and scheduling, attempt to use buses to provide a service that is of a higher quality than an ordinary bus line. Each BRT system uses different improvements, although many improvements are shared by many BRT systems. The goal of such systems is to at least approach the service quality of rail transit while still enjoying the cost savings of bus transit. The expression BRT is mainly used in North America; in Europe and Australia, it is often called a busway, while elsewhere, one may speak of quality bus or simply bus service while raising the quality.
EtymologyBus rapid transit takes part of its name from rapid transit which describes a high-capacity rail transport system with its own right-of-way, its alignment often being elevated or running in tunnels, and typically running long trains at short headways of a few minutes. Because of the name similarity one tends to associate the merits of rapid transit also with the newer BRT expression. BRT encompasses a broad variety of modes, including those known or formerly known as express buses, limited busways and rapid busways and even BHNS in France (Bus à Haut Niveau de Service). Ironically, the term bus rapid transit does not refer to the speed of BRT buses. Typical transit speeds of BRT systems range from 12 to 30 miles per hour (19 to 48 km/h) which compares well with surface running LRT.[1] Main featuresThese bus systems can come in a variety of forms, from dedicated busways that have their own rights-of-way (e.g., Ottawa's Transitway or the Pittsburgh MLK East Busway) to bus services that utilize HOV lanes and dedicated freeway lanes (e.g., Honolulu's CityExpress) to limited stop buses on pre-existing routes. An ideal bus rapid transit service would be expected to include most of the following features:
Recent technological developments such as bi-articulated buses and guided buses have benefited the set up of BRT systems. The main developments are:
Acceptance of BRT may increase using trolley-buses, because of the lower gaseous and noise emissions. The price penalty of installing overhead lines can be repaid over a longer period by the savings from centrally generated electricity[citation needed]. Controversies
Opponents[who?] of bus rapid transit initiatives argue that BRT is not an effective replacement for light rail or subway services. They argue that in order for BRT to have greatest effect, it must have its own right-of-way requiring space and often construction costs. A regular bus service would share the road with cars; a BRT service operating in mixed traffic would be subject to the same congestion, delays, and jarring and swaying rides as do ordinary city buses. Furthermore, signal priority systems, which are often the sole factor differentiating BRT from regular limited-stop bus service (most notably in Los Angeles' extensive "Rapid" system), might cause severe disruptions to traffic flow on major cross streets. Opponents[who?] argued that this merely redistributes, rather than reduces, the traffic congestion problems that BRT systems are designed to alleviate. On the other hand, many light rail systems also utilize signal priority system and railroad-style crossing gates (with long cycle times) to speed up service as well, and in the same time both BRT and light rail get more persons across a road junction than car traffic. The widespread belief that the most effective method of solving traffic congestion problems is to discourage private car usage and the preferential treatment of buses in intersections, along with the conversion of some roads to exclusive bus right-of-ways, will help. Also, the original system designed in Curitiba, Brazil, aimed to promote development along the BRT corridor to make better accessbile. Retrofitting such a system in cities that have a different pattern of development may not be adequate to address the issues in those cities, or in most cases may be an aid for politicians to 'eco-wash' their stay in office. The original system is also part of a three street network that does not impede road width or road accessibility for traditional usage. It does not affect the character of the street, and clearly, that is the success story of Curitiba. Having dedicated lanes on narrow roads may adversely affect activity on those roads, and could lead to a situation like Howard St in Baltimore which has dedicated Light Rail lanes, but is increasingly treated like a backyard or a corridor for movement, and its distinct lack of character undermines its neighborhood. Another prime example of a disastrous effect of BRT has been in New Delhi due to segregation of existing ROW from 3-mixed traffic lanes to 2:1 Mixed traffic and BRT lanes. One of its most prime, widest main roads started having huge traffic pileups ever since the BRT was inaugurated in April, 2008. Due to Level of Service came down and delays at the intersections increased. Then some of the mixed vehicle lane traffic has been diverted to the secondary network of the corridor. However, it should be noted that much of the controversy arises from the wide range of definitions of BRT. Comparison with other forms of mass transitBRT attempts to combine the advantages of a metro system (exclusive right-of-way to improve punctuality and frequency) with the advantages of a bus system (low construction and maintenance costs, does not require exclusive right-of-way for entire length, at least at the beginning). Compared to standard bus service BRT systems with dedicated right-of-way and thus an increased average transport speed can provide more passenger-miles with the same number of rolling stock and personnel. They also offer the prospect of a more fluent ride than a normal bus immersed in stop-and-go traffic. It is simplistic to use calculations to predict the capacity of BRT and normal buses and say typical buses are 12 metres (40 feet) long, articulated buses 18 metres (60 feet). The maximum length for a street-running tram consist (in Germany) is 75 metres (about 250 feet). Light rail systems running in-street are limited to one city block in length, unless, as in Sacramento, CA, they are allowed to obstruct intersections when stopped. Metro trains can be 240 m (about 800 feet) long. With similar dwell times in stations the capacity of rail systems would scale with the length of the train. For instance, a light rail system running on two-minute headways with 200-passenger cars operating as single units could carry 6,000 passengers per hour. It should theoretically therefore carry 12,000 passengers per hour with two-car trains, and 24,000 per hour with four-car trains. In practice real world delays multiply and headways become disrupted causing a practical limitation of around 12 to 19,000[2] Comparison with light railThe best source of information capacity comes from a study that actually stood at the side of the road and counted passengers. As quoted in.[3] a survey by the UK Transport Research Laboratory revealed: Exhibit 3-22: Maximum Observed Peak Hour Bus Flows, Capacities, and Passenger Flows at Peak Load Points on Transitways Measured Peak Hour Passenger Flow (Passengers / Hour) Designated Lane: Ankara, Istanbul, Abidjan 7,300 – 19,500 Designated Lanes with Feeders Curitiba, Brazil 13,900 – 24,100 Designated Lanes with Bus Ordering (Travelling in Clusters) Porto Alegre 17,500 – 18,300 Designated Lanes with Overlapping Routes, Passing at Stations and Express Routes Belo Horizonte, São Paulo 15,800-20,300 Bogotá 35,000-40,000 However, many BRT systems such as OC Transpo Transitway, Ottawa and South-East Busway, Brisbane are based on multiple bus routes sharing a common dedicated busway to bypass congestion, especially to/from a central business district. In this form, the BRT system passenger capacity is limited by vehicle capacity times vehicle headway of the busway. As buses can operate at headways as low as 10 seconds between vehicles (compared to at least one minute headways for rail vehicles), actual busway capacity can reach passenger rail capacities. At the high end, the Lincoln Tunnel XBL bus lane carries 62,000 commuters in the 4 hour morning peak, more than any Light Rail Line. However, this lane has no stops in it. Stops increase the headway and limit a BRT lane to about 10,000 passengers per hour, even with passing lanes in the stations. Note that this is still five times the number carried in the automobiles in a congested freeway lane. At it's busiest point, Brisbane's South-East Busway currently carries in excess of 15,000 commuters per hour per direction, and is not yet considered at capacity. Many agencies make a clear distinction between a pure BRT, which is in exclusive lanes, and a more compromised form in mixed traffic. For example, the Los Angeles Orange Line runs entirely in an exclusive lane and therefore achieves speed and reliability comparable to rail. Because it is functionally equivalent to rail, the Los Angeles County Metropolitan Transportation Authority presents this line as part of its rail transit system, distinct from its "Rapid" lines, which run in mixed traffic. The typical diesel engine on the bus causes noticeable levels of air pollution, noise and vibrations. Through developing buses as hybrid vehicles and the use of new forms of trolleybus BRT designers hope to increase ride quality and decrease pollution. As the energy use for acceleration is proportional to the vehicle mass, electric traction allows lighter vehicles, faster acceleration and energy that can be fed back into batteries or the grid through regenerative brakes. Regenerative braking is standard on modern rail systems. In contrast to BRT, both Light Rail and rapid transit require the placement of rails for the whole line. The tram usually avoids the high additional costs for the engineering structures like tunnels that need to be built for metros. Rail tends to provide a smoother ride and is known to attract significantly higher passenger numbers than road-based systems. Many BRT designers have used the need to construct power conduit systems as an argument against Light Rail, but a new proposal, known as ultra light rail, would have trams carry their own power, much like a bus, at a significant energy savings due to lack of rolling resistance. In larger towns and cities, such as Essen, Germany and Pittsburgh, USA, it is common for a right of way exclusive to public transport to be used by both light rail and buses. In tunnels or tunnel systemsA special issue arises in the use of bus vehicles in metro structures. Since the areas where the demand for an exclusive bus right-of-way is apt to be in dense downtown areas where an above-ground structure may be unacceptable on historic, logistic, or environmental grounds, use of BRT in fully underground tunnels may not be avoidable. Since buses are usually powered by internal combustion engines, bus metros raise ventilation issues similar to those of tunnels. In the case of tunnels, powerful fans typically exchange air through ventilation structures on the surface, but are usually placed in a location as remote as possible from occupied areas to minimize the effects of noise and concentrated pollution. A straightforward way to deal with this is to use electrical propulsion in tunnels and, in fact, Seattle in its Metro Bus Tunnel and Boston in Phase II of its Silver Line are using this method in their respective BRTs. In the case of Seattle, dual-mode (electric/diesel electric) buses manufactured by Breda were used until 2004, with the center axle driven by electric motors obtaining power from a trolley wire through a trolley pole in the subway, and with the rear axle driven by a conventional diesel powertrain on freeways and streets. Boston is using a similar approach, after initially using electric trolleybuses to provide service pending delivery of the dual mode vehicles in 2005. In 2004, Seattle replaced its "Transit Tunnel" fleet with diesel-electric hybrid buses, which operate similarly to hybrid cars outside the tunnel and in a low-noise, low-emissions "hush mode" (in which the diesel engine operates but does not exceed idle speed) when underground. The necessity for providing electric power in these environments brings the capital and maintenance costs of such routes closer to light rail and raises the question of building light rail instead. In Seattle, the downtown transit tunnel retrofitted for conversion to a shared hybrid-bus and light-rail facility in preparation for Seattle's Central Link Light Rail line to be operating in 2009. List of systemsImplementation by countrySee also
References
Developing Cities, Transport and Road Research Laboratory Research Report 329, Department of Transport, Crowthorne, Berkshire, United Kingdom, 1991 External links
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