A small- to mid-sized trailer. Since most travel trailers do not feature an engine of their own, they require towing from another vehicle. Also referred to as “conventional trailers,” these types of rigs have an A-frame and coupler and are attached to a ball mount on the tow vehicle. Travel trailers are available with one, two or three axles. Depending upon tow ratings, conventional trailers can be towed by trucks, cars or sport-utility vehicles.