Low-floor bus technology has evolved substantially. European fleets adopted low-floor bus technology in the 1980s. Early models had only a partial section of low-floor access (with a sloped floor or steps to access the rear of the vehicle). Full section, low-floor vehicle designs are now available.
Low-floor buses comply with the requirements of the Americans with Disabilities Act (ADA) of 1990 and concurrently reduce time needed to service persons using mobility aids. Access to the vehicle can either be at raised platforms (providing level boarding) or using an on-vehicle ramp which flips down to bridge the gap between the step and the curb. In contrast, high-floor buses require lifts which are difficult to maintain under all operating conditions. A curb height of at least 150mm (5.85 in) is desirable to permit easy access from curb to the vehicle level.
Low-floor vehicles permit the possibility of level boarding, an effective way of reducing dwell time at stations. A high-level bus with internal steps cannot be docked with a raised station platform (see Stop Location, Design and Spacing).
With low floor buses, one concern is the ability to move the bus close enough to the raised station platform to permit level boarding without damaging the vehicle's tires or structure. One solution to this problem is automatic control of vehicles to provide precision docking. In August 1997, New York City Transit successfully demonstrated low-floor buses with full automatic control. The buses were equipped with vision and radar sensors to control the bus in both lateral and longitudinal directions. Such technology could also be used to steer a bus close to a raised platform (see TCRP Report 41). The use of mechanical systems to guide the vehicle, particularly at stations, is also an option.
Bus manufacturers offering low-floor bus designs for the North American market include: Gillig, Neoplan USA, New Flyer Industries, North American Bus Industries, Nova Bus, and Orion Bus Industries.
Increasing the number of doors from two to three for a 40 foot conventional bus potentially increases the passenger handling capability at stops or stations by 50 percent. Combining additional doors with level boarding and off-vehicle fare collection can reduce dwell time to a minimum. The number and location of doors, however, needs to be carefully integrated with the vehicle's structural support systems to prevent any compromise of crashworthiness.
Location of the doors is also of concern. Some BRT systems may require left-sided doors to access bus lane or busway stations with central platforms without having to engage in complicated and time consuming crossing maneuvers. Two-sided BRT vehicle designs may also be desired to support double loading at side platform stations, emulating light or heavy rail operations.
For an interesting case study of poor internal configuration giving rise to problems which stimulated a search for better alternative configurations, see TCRP Report 41, §188.8.131.52, highlighting the STCUM's deployment of low-floor buses in Montreal.
|Low-floor, compressed natural gas (CNG) bus operating on the Lymmo downtown circulator route in Orlando, Florida. This bus sports a Leonardo DaVinci design.|
Another option is the electric trolley bus, powered by catenary (overhead wires). The wires can be considered unsightly, although they are very similar to catenary for light rail. Electric trolley buses are proven technology, have no emissions from the tailpipe, and are the quietest transit mode of all.
1. There are no doorway clear width requirements set by ADA for buses, except by implication in that a clear space of 30 in (769 mm) by 48 in (1231 mm) needs to be provided for a securement location sited as close as possible to the entryway. There is, however, a clear width requirement of 32 in for passenger doorways on vehicle sides of rail cars (§1192.53 (a), FR Vol. 56, No. 173, Sept. 6, 1991). To the extent that BRT emulates an LRT operation, the use of a 32 in (820 mm) clear width requirement makes sense.