The term "demand responsive transportation" (DRT) refers to modes of transport that adjust the supply of services to the demand at any one time, including variations in schedule and/or variations in trip route. DRT is an important, but often overlooked, component of public transportation that provides unique opportunities and challenges for accessibility. The success of transportation network companies (TNCs), like Uber and Lyft and other vehicle sharing services, is rapidly changing the DRT scene, creating both opportunities and challenges for accessible transportation. Some sources use DRT as a synonym for special transport services (STSs), or paratransit, as it is called in North America; some exclude STS from their definition, focusing on services available to a wider rider base; some include taxis; some exclude taxis. Mobile phones and crowdsourcing are disruptive technologies that are changing the nature of DRT. These two technologies have enabled the rapid development of vehicle sharing services.