Bus rapid transit

Bus rapid transit (BRT) is a term applied to a variety of public transportation systems using buses to provide faster, more efficient service than an ordinary bus line. Often this is achieved by making improvements to existing infrastructure, vehicles and scheduling. The goal of these systems is to approach the service quality of rail transit while still enjoying the cost savings and flexibility of bus transit.^[1] The expression BRT is mainly used in North America; in Europe and Australia, it is often called a busway, while elsewhere, it may be called a quality bus.

Etymology

Bus rapid transit takes part of its name from rail rapid transit, which describes a high-capacity urban public-transit system with its own right-of-way, multiple-car trains at short headways, and longer stop spacing than traditional streetcars and buses. BRT, however, uses buses on a wide variety of rights-of-way, including mixed traffic, dedicated lanes on surface streets, and busways completely separated from traffic.

Typical transit speeds of BRT systems range from 17 to 30 miles per hour, which can compare with surface running light rail.^[2]

Main features

BRT systems come in a variety of forms, such as dedicated busways with their own rights-of-way (e.g., the Ottawa Transitway or the Pittsburgh MLK East Busway), bus services using HOV lanes, dedicated freeway lanes (e.g., Honolulu's CityExpress) and limited-stop buses on pre-existing routes.

Separated line for TransJakarta buses in Jakarta, Indonesia

An ideal bus rapid transit service would be expected to include most of the following features:

Bus only, grade-separated (or at-grade exclusive) right-of-way : A dedicated bus lane allows the bus to operate separately, without interference from other modes of traffic. Although buses have a long turning radius, busways can be engineered to tighter standards than an open roadway, reducing construction costs while still assuring safe operation.
- A bus-only right-of-way may be elevated or may even be modified rail right-of-way.
- A transit mall or bus street can be created in an urban center by dedicating all lanes of a city street to the exclusive use of buses.
- Low-cost infrastructure elements that can increase the speed and reliability of bus service include bus turnouts, boarding islands, and curb realignments.
Comprehensive coverage: BRT systems can also share existing roadways with other traffic or use bus lanes that restrict other traffic from a portion of the roadway. Service along public roadways can be improved by taking advantage of bus priority methods.
Serves a diverse market with high-frequency all day service : A BRT network with comprehensive coverage can serve a diverse market (all income ranges) by moving large numbers of people between locations quickly and reliably throughout the day, while maintaining a comfortable riding experience.^[1] These characteristics are essential to satisfying the demands of a diverse market or offering high-frequency service without heavy subsidy.
Bus priority: 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 bus streets, because general-purpose traffic does not intervene between buses and traffic signals.
Vehicles with tram-like characteristics
Recent technological developments such as bi-articulated buses and guided buses have benefited the set-up of BRT systems. The main developments are:
- Improved riding quality (Use of guided bus and powertrain control technologies for smoother operation),
- Increased capacity (articulated and double-decker),
- Reduced operating costs (hybrid electric powertrain).
A specific image with a brand name (Viva, Max, TransMilenio, Select) marking stops and stations as well as the buses.^[3] The system's brand identity contributes to its attractiveness as an alternative to driving cars.^[4]
Off-bus fare collection: Conventional on-board fare collection slows the boarding process, particularly when different fares are collected for different destinations and/or classes of passengers. Some systems collect fares upon entering an enclosed bus station or shelter area prior to bus arrivals (similar to fare collection at a kiosk prior to entering a subway system). This allows passengers to board quickly through all doors of a stopped bus.
Level boarding: Many BRT systems also use low-floor buses (or high-level platforms with high-floor buses) to speed passenger boardings and enhance accessibility.
Stations: High-quality BRT systems often feature significant investment in enclosed stations which may incorporate attractive sliding glass doors, staffed ticket booths, information booths, and other more standard features listed above. This style of station is seen in Bogotá's TransMilenio and some other cities in Latin America that have adopted BRT systems. Most North American systems use open platform stops, or shelter-style platform stops.

All of the above characteristics were noted as features of Bogotá's TransMilenio, described as a "model BRT system" in the National Bus Rapid Transit Institute's May 2006 report. TransMilenio serves Bogotá with high-capacity articulated buses, which passengers can board through three doors. A smart card system is used for off-board fare collection.^[5]

In cities and large towns, such as Amsterdam, Essen (Germany), Pittsburgh and Seattle, it is common for a right of way exclusive to public transport to be used by both light rail and buses, and in some cases taxis.

Comparison with other forms of mass transit

File:Estacionelevada.jpg

TransMilenio BRT system in Bogotá, Colombia, holds a record 40,000 passengers per hour.

BRT attempts to combine the advantages of a metro system (noticeably right-of-way, which improves punctuality and frequency) with the advantages of a bus system (low construction and maintenance costs, low vehicle costs, right-of-way not required for entire length, and for the ability of feeder bus services to join a trunk busway).

Comparison with conventional bus routes

The dedicated right-of-way lanes of BRT systems allow them an increased average vehicle speed, to provide more passenger miles with the same number of vehicles and personnel than conventional bus services. A smoother ride can also be expected, because the BRT is not immersed in stop-and-go traffic.

Comparison with light rail

Primary considerations in choosing between light rail and bus rapid transit systems are the differences in construction costs, operating costs, capacity, adaptability and image.

Proponents of light rail point out that the operating costs of BRT are not necessarily lower than light rail. The typically larger light rail vehicles enjoy reduced labor costs and the unit capital cost per passenger can be lower than a BRT system.^[6] In contrast to BRT, light rail and tram systems require the placement of rails for the entire line. The tram usually avoids the high additional costs for engineering structures, such as tunnels, that need to be built for metros. Rail tends to provide a smoother ride, making it more attractive to riders than road-based systems.

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. Theoretically, it should carry 12,000 passengers per hour with two-car trains, and 24,000 per hour with four-car trains. In practice, real-world delays and headway disruptions cause a practical limitation of around 12,000 to 19,000.^[7]

A survey by the UK Transport Research Laboratory reported the following peak passenger flows (passengers per hour) for BRT transitways:^[8]

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
TransMilenio, Bogotá 35,000 - 40,000 ^[9]

Many BRT systems, such as Ottawa's OC Transpo and Brisbane's South-East Busway, 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's passenger capacity is limited by vehicle capacity multiplied by 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. In the NBRTI's May 2006 report, average headways of 13 seconds at busy intersections were observed in the TransMilenio BRT system.^[5]

At the high end, the Lincoln Tunnel XBL bus lane between New Jersey and New York carries 62,000 commuters in the 4-hour morning peak, more than any light rail line. However, this lane has no stops in it. Furthermore, a very large terminal station is required (Port Authority Bus Terminal) to accept and dispatch passengers. Stops increase the headway and limit a BRT lane to about 10,000 passengers per hour, even with passing lanes in the stations. This is still five times the number carried in the automobiles in a congested freeway lane. At its busiest point, Brisbane's South-East Busway currently has the capacity for in excess of 15,000 commuters per hour per direction.^[10]

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.

Environmental Problems

The typical diesel engine on the bus causes noticeable levels of air pollution, noise and vibration. With hybrid vehicles and the 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 many modern rail systems.

A BRT system can use trolley-buses to lower gaseous and noise emissions. The price penalty of installing overhead lines could be offset by the system's environmental benefits potential for savings from centrally generated electricity, especially in cities where electricity is less expensive than other power sources. In addition, most trolleybus applications can be converted to light rail with the only extra expense being the laying and maintenance of tram tracks in the street.

In tunnels or tunnel systems

A 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. Seattle in its Metro Bus Tunnel and Boston in Phase II of its Silver Line are using this method in their 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.^[11]^[12]

The need to provide electric power in these environments brings the capital and maintenance costs of such routes closer to those of light rail, and raises the question of building light rail instead. In Seattle, the downtown transit tunnel was retrofitted for conversion to a shared hybrid-bus and light-rail facility in preparation for Seattle's Central Link Light Rail line, which opened in July 2009.

Aesthetics of Bus Rapid Transit

Bus rapid transit vehicles, station stops, and collateral elements are typically free of advertising (which is common to many public transit systems). This is not always the case, however: Los Angeles County Metropolitan Transportation Authority (Metro) has video advertising on board the buses.

Think Tanks and Blogs

In the USA there are at least three think-tanks directly involved in lobbying for BRT systems: 1) The National Bus Rapid Transit Institute was established by the US Federal Government in January 1991, and is housed at the Center for Urban Transportation Research (CUTR) at the University of South Florida, and 2) the Bus Rapid Transit Policy Center promotes BRT technology over light rail, and 3) the Institute for Transportation and Development Policy.

The objectivity of the work of CUTR and at least one of its employees has been questioned.^[13]

The World Resources Institute and the CityFix series of blogs, funded by EMBARQ (whose funders include the Shell Foundation), also issue frequent reports that support BRT.

The Streetsblog.org series of blogs and Streetfilms.org videoblog also are frequent proponents of BRT.