TransitMobile is a mobile application that provides logistic information to drivers in Oklahoma community-based paratransit operations. Passenger reservation information is transferred from the home agency to in-vehicle mobile devices to notify the drivers as reservations are made in real-time. In this study, user testing and a questionnaire were used to evaluate the usability of the application. Task completion times and subjective measures from the questionnaire pointed to areas of the system design that caused errors. The effects of practice revealed the importance of training for drivers in the field. While TransitMobile is a promising application, the system in which it functions is complex, and users must receive adequate training in order to use the application to its fullest potential.