The eligibility criteria for the scheme are set out in chapter VIII of the GLA Act 1999. They are supplemented by Department for Transport guidance on assessing eligibility for concessionary travel. There is currently no work being undertaken to expand these criteria as they are set out in statute and guidance made elsewhere. Nevertheless, some people with hidden disabilities such as autism may already qualify for the scheme. As there are many types of disabilities, eligibility is determined by the London boroughs on a case-by-case basis against existing criteria.