SCCA defines ProRally as "a flat-out race over closed sections of rural roads by modified production automobiles. It is different than most car races in that:
Competitors race one car at a time against the clock, usually at one minute intervals.
Flat-out racing is done on limited access roads, blocked off from "civilian" traffic, rather than on prepared tracks.
Events can be several hundred miles long, often lasting for several days."
http://www.oregontrailrally.com/
http://www.scca.org/amateur/performa...003/index.html