High-floor describes the interior flooring of commuter vehicles primarily used in public transport such as trains, light rail cars and other rail vehicles, along with buses and trolleybuses. Interior floor height is generally measured above the street surface or above the top of the rail. High-floor designs usually result from packaging requirements: mechanical items such as axles, motors, crankshafts, and/or transmissions, or luggage storage spaces are traditionally placed under the interior floor of these vehicles. The term is used in contrast with low-floor designs, which offer a decreased floor and entry height above the street surface. Since low-floor designs generally were developed after high-floor vehicles, the older high-floor design is sometimes also known as conventional or the “traditional” design. Rail Heavy rail A rail vehicle of conventional or high-floor design usually has a flat floor ranging between above the top of the railhead (ATOR). To enhance accessibility and optimize dwell times, railway platform heights at stations are standard to allow level boarding for commuters on high platforms. According to one definition, level boarding means the gap between the platform and the floor of the track varies by no more than horizontally and vertically. Level boarding is also known as stepless entry since passengers do not have to negotiate a staircase to board the passenger car. For newly constructed routes, routes primarily located in tunnels, or routes with a dedicated right of way and enough space, high platforms are usually preferred, since high-floor vehicles are cheaper to manufacture, and have better operating characteristics. High platforms do have significant advantages beyond level boarding for wheelchair accessibility. Physically disabled passengers (e.g. those using wheelchairs or who have difficulties climbing stairs) also benefit, as do travelers pulling wheeled luggage or small folding shopping carts. Even physically non-disabled passengers can board a railcar more rapidly if they do not have to climb stairs to enter, reducing dwell time at a stop, and reducing overall travel time. In addition, high-platform railcars have more floor space for passengers if space is not required for stairways, and wheelwells needed to accommodate train bogies. Because bilevel rail cars have two passenger levels within a standard height rail car, the lower level, where passengers board, is generally lower than a conventional high-floor car. Hence level boarding with a bilevel car is accomplished using a lower platform, as low as ATOR. Light rail Because tram/light-rail/streetcar vehicles often share loading gauge sizes