Description & Facts: Casper is the second largest city in Wyoming, after Cheyenne. Casper Area Transportation Coalition - closest Natrona county has to a bus system. The cost for elderly and disabled is $2.00 per one way trip, $5.00 for general public and $1.00 for children 12 and under when accompanied by an adult traveling to the same destination. Passengers are required to register the first time they use the service and purchase trip tickets.