The US Government Accessibility Office (GAO) conducted research on the barriers disabled passengers' experience during the airport experience and how airport accessibility can help or hinder it. The paper, 'Passengers with Disabilities: Airport Accessibility Barriers and Practices and DOT's Oversight of Airlines' Disability-Related Training', found that passengers with disabilities face infrastructure, information, and customer service barriers at U.S. airports, according to representatives of selected airports, disability advocacy organizations, as well as a review of relevant literature. The infrastructure barriers can include complex terminal layouts and long distances between gates and can be difficult for some to navigate. A passenger might not receive appropriately sensitive service, such as wheelchair assistance, at the airport, although the service provided is required by the Air Carrier Access Act of 1986 (ACAA) regulations.