A low-floor bus is a bus that has no steps between one or more entrances and part or all of the passenger cabin. Being low floor improves the accessibility of the bus for the public, particularly the elderly or infirm, or those with push chairs, and increasingly, those in wheelchairs.
In the modern context, “low floor bus” refers to a bus that is accessible from a certain minimum height of step from ground level, to distinguish it from some historical bus designs that did feature a level interior floor throughout but with a relatively high floor height.
Many low-floor buses are low-floor over only a part of the bus, with the rear section raised to accommodate powertrain equipment. Van Hool has a series of “side-engine rear-drive” buses that puts the engine off to one side of the cabin longitudinally, to maximize usable cabin space.
Most bus manufacturers achieve a low floor height by making rear-engined rear-wheel drive buses with independent front wheels, so that no axle is needed to pass under the floor of the passenger compartment.
For smaller buses, such as midibuses, the low-floor capability is achieved by placing the front wheels ahead of the entrance. One of the last types of buses to gain low-floor accessibility as standard was the minibus, where a similar front-wheel arrangement allows around 12 seats and a wheelchair space to be accommodated in very small low-floor minibuses, such as the Optare Alero and Hino Poncho.
Accessibility was previously achieved in paratransit type applications, which use small vehicles with the fitment of special lifts. The inception of small low-floor buses has allowed the development of several accessible demand-responsive transport schemes using standard ‘off-the-shelf’ buses.
Low-floor buses usually include an area without seating (or seating that folds up) next to at least one of the doors, where wheelchairs and perambulators can be parked. This is sometimes not the only purpose of this area, though, as many operators employ larger standee areas for high occupancy at peak times. Despite the space existing, operators may also insist that only one or two wheelchairs or pushchairs can be accommodated unfolded, due to space/safety concerns.
An interesting implementation of the low floor design exists in Australia, where Custom Coaches makes a “Hybrid” variant of its CB6O bodywork. These buses combine a smaller low floor area with a small underfloor bin for some luggage. Whilst these buses do not provide a full amount of luggage space, they can be used to house more luggage than what can be held inside the bus itself. Another drawback is the arrangement means the section of the bus that is at kerb height is very short-consisting of enough space to house the wheelchair area and then rising up, to accommodate the luggage bin. These buses also lack the ability to have a centre door.
A disadvantage of the low floor is accommodating the bus’s own wheels. With the low floor, the wheels protrude into the passenger cabin, and need to be contained in wheel pockets of waist height, and this occupies space which would otherwise be used for seating. Seating layout for a low-floor bus therefore requires careful design
Low floors can be complemented by a hydraulic or pneumatic ‘kneeling device’, which can be used when the bus is not in motion, tilting it or lowering it at the front axle even further, often down to normal kerb height. Though such technology has been available and in use on high-floor buses since the 1970s, it is of significant utility on low-floor vehicles only where it enables less-mobile passengers to board and leave the vehicle without help from others. Many vehicles are also equipped with wheel-chair lifts, or ramps which, when combined with a low floor, can provide a nearly level entry.
