Kneeling bus

A low-floor bus is a bus or trolleybus that has no steps between the ground and the floor of the bus at one or more entrances, and low floor for part or all of the passenger cabin. A bus with a partial low floor may also be referred to as a low-entry bus in some locations.

"Low floor" refers to a bus deck that is accessible from the sidewalk with only a single "step" with a small height difference, caused solely by the difference between the bus deck and sidewalk. This is distinct from "high-floor", a bus deck design that requires climbing one or more steps (now known as step entrance) to access the interior floor that is placed at a higher height. Being low-floor improves the accessibility of the bus for the public, particularly the elderly and people with disabilities, including those using wheelchairs and walkers. The first low floor bus (LAZ 360) was created in the USSR at the Lviv Bus Plant (LAZ) in 1965. It was powered by a gasoline V8 engine that was linked to a generator. The generated electricity powered electric motors on all 8 wheels.

Low-floor buses are generally divided into two major types: fully low-floor buses with a low floor throughout the length of the bus (more popular in Europe), and low-entry buses with step-free access to only a part of the bus, most commonly between the front door and the middle door (more popular in North America). In North America, both types are commonly called low-floor, as the majority of the vehicle has a low floor, without steps at the doors.

The main reason for choosing a low-entry configuration is to allow better placement for the powertrain and other technical equipment in the raised floor section, in addition to allowing a more comfortable ride on rough roads. Some manufacturers use the initials LF or L in their model designations for fully low-floor models (or in the case of German manufacturers, NF or N, based on the German word Niederflur, which means low floor), and in North America buses that are partially low-floor are often also designated LF. In some countries, LE, short for Low Entry, is used by some manufacturers in their model designations for low-entry buses.

Most bus manufacturers achieve a low floor height by making rear-engined rear-wheel drive buses with independent front suspension, so that no axle is needed to pass under the floor of the front part of passenger compartment, or a lowered front axle. Some full low-floor buses also have a lowered rear axle, while the rear axle is not an issue on a low-entry bus.

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