DRIVING YOUR OWN VEHICLE
Driving in Mexico is one of the finest ways of seeing and experiencing the country. The pace is your own and spontaneity is guaranteed. The road system is consists of Free and Toll roads.
The Toll roads offer security and quality. The Free roads offer no tolls (often quite expensive) and a much more personal and varied scenery. Toll roads are patrolled by both the police and “green angels,” a government service in Mexico that provides free minor emergency vehicle service to travelers (tire repairs, gas, etc). The Free roads are less patrolled and are sometimes in bad repair with heavy local traffic.
Here is a convenient cost/destination website by the Mexican Government Secretariat of Transportation. It provides exact toll costs and estimated fuel costs for many types of vehicles.
http://aplicaciones4.sct.gob.mx/sibuac_internet/ControllerUI?action=cmdEscogeRuta&eligeIdioma=si
THE BUS SYSTEMS