Open car carriers are open to the elements, such as dust & weather conditions.  However, open transport is the typical type of service offered in the auto transport industry.  If you have ever seen those big rigs on the road with all of the cars on the trailer, those are open carriers.  These carriers range from 8 to 10 cars on average.  Some carriers have F350s with wedge trailers on the back that accommodate 2 to 4 cars (usually for inoperable vehicles, large vehicles, short distances, and freight.)  This method of transportation is cheaper than the enclosed route because there are far more open carriers regularly available.  More people choose open transport because of the availability and cost effectiveness, but enclosed is the way to go when you have an exotic vehicle, show car, race car or a vehicle of extreme sentimental value