In the USA during the 1920s, concerns were expressed that large lifts were being overloaded owing to the lift attendants in the cars pushing passengers into their cars. On group systems this was aggravated by the human despatchers forcing passengers into the cars. The result was the density of the passenger load increased as the cars got bigger. Non-domestic buildings were designed in the USA for a uniformly distributed load of 60 pound per square foot (psf) on open areas of building floors and this was used for lift car floors. To ensure passenger safety the load bearing was increased to 100psf for lifts carrying 10,000lb (A17.1:1925), and in 1937 to 127.5psf (A17.1:1937) for lifts carrying 37,500lb. This resulted in a nonlinear relationship between passenger load and the available car area on which they stand. This can be seen in Table 6 of BS EN81-20:2020/BS ISO8100-1:2019.