An open car carrier is the familiar car hauler seen on highways: a truck pulling a trailer with ramps, usually on two levels, and no walls or roof. Open carriers are the workhorse of everyday vehicle shipping, including new-car deliveries to dealers and most auction purchases.
Because open trailers carry several vehicles at once and there are many of them on the road, they are the most economical option and usually the easiest to schedule. The tradeoff is exposure. Vehicles ride in open air and can pick up road dust, rain, bugs and, occasionally, small chips from debris. For a typical used car, that is an accepted part of shipping, and a wash at delivery handles most of it.
For dealers, auctions and marketplaces, open transport is the sensible default for daily drivers and most retail inventory. Enclosed transport makes more sense for collector, exotic or freshly painted vehicles. Position on the trailer also matters to some shippers, and a top load spot avoids drips from vehicles above.
In an instant quote, open or enclosed is one of the main inputs, and open is usually the lower price of the two. Compare with an enclosed car carrier and read open vs. enclosed car transport.