49 CFR §37.189

1. (a)This section applies to private entities primarily in the business of transporting people, whose operations affect commerce, and that provide demand-responsive OTRB service. Except as needed to meet the other requirements of this section, these entities are not required to purchase or lease accessible buses in connection with providing demand-responsive service.
2. (b)Demand-responsive operators shall ensure that, beginning one year from the date on which the requirements of this subpart begin to apply to the entity, any individual with a disability who requests service in an accessible OTRB receives such service. This requirement applies to both large and small operators.
3. (c)The operator may require up to 48 hours' advance notice to provide this service.
4. (d)If the individual with a disability does not provide the advance notice the operator requires under paragraph (a) of this section, the operator shall nevertheless provide the service if it can do so by making a reasonable effort.
5. (e)To meet this requirement, an operator is not required to fundamentally alter its normal reservation policies or to displace another passenger who has reserved a seat on the bus. The following examples illustrate the provisions of this paragraph (e):