For both highway and transit modes, private contract services represent the most common form of private sector involvement in surface transportation project and service delivery. For the highway mode this includes contract planning and environmental studies, facility and right-of-way maintenance, and operations, including the operation of transportation management centers and various ITS services. Transit agencies have long contracted for the operation of some or all of its modal services with the private sector, especially paratransit services for senior and persons with disabilities. In addition, many transit agencies contract for maintenance services on some or all of their vehicles, facilities, and infrastructure.