The paper examines the safety provided by bus roofs in accidents. Test results show that static, vertical loads have little to do with actual accident results and that corresponding tests are not indicative of security. A diagonal force of recoil acts upon the roof edge in accidents; the components of this force in the roof plane determine the resulting plastic deformation. Consequently, load-bearing characteristics and energy absorption properties must be tested in an oblique direction. Based on the results of the crash- and laboratory tests cited, suggestions for roof improvements were implemented. Currently, some buses are being factory-equipped with rollbars as a result of this research.
Standard testing procedures were established for accident-safety. Bus models which pass this test offer a certain level of security which is generally higher than that currently afforded. However, many possible influences were not taken into account and the present testing procedure must be further developed.