Under the Transport Act 1985 the Disabled Persons Transport Advisory Committee (DPTAC) (or commonly DiPTAC) was established to provide independent consultation on accessibility issues. In the same year, the first low floor bus specification was drafted by DPTAC. The Disability Discrimination Act 1995 provided for the completion of the Public Service Vehicles Accessibility Regulations 2000, which specified that all new public service vehicles over 22 seats should be low floor from 31 December 2000, with smaller vehicles mandated from 1 January 2005. The 2000 regulations do not require retro-fitting of pre-existing vehicles or the enforced sale of non-compliant existing vehicles, allowing operators to retain a high floor vehicle until "the end of their economic life". In reality, as the prevalence of low floor buses spreads, combined with grants/incentives, it is likely that the prevalence of high floor vehicles in the national fleet will markedly reduce before all buses were de-registered by 27 October 2014. In the past, in times of reduced economic investment, it was not uncommon for service buses to be used for 15 to 20 years.