Mountain Area Regional Transit Authority, a rural transit agency, was formed December of 1993 under a joint powers authority between the City of Big Bear Lake and San Bernardino County.

Mountain Transit provides Fixed Route, Off-the-Mountain (OTM), and Dial-a-Ride service throughout the rural San Bernardino Mountain communities of the Big Bear Valley, Crestline, Lake Arrowhead, and Running Springs. Off-the-Mountain commuter service connects these communities and the city of San Bernardino, making connections with Omnitrans, Metrolink,  and other various stops. Mountain Transit operates Trolley service providing transportation between local restaurants, hotels, ski resorts, and shopping venues throughout the City of Big Bear Lake.

Mountain Transit transports between 12,000 and 15,000 passengers per month dispersed between the Fixed Routes, Dial-A-Ride, and OTM services within a service area of several hundred miles. Peak transportation times are between December and March due to the holiday season and the winter snow activities on the mountains.