From asmartcar.com
Can the smart be towed behind an RV?
When towing behind another vehicle, for example, an RV, the manufacturer strongly recommends all four wheels be off the ground and the car well secured on a trailer. This will not only save your tires and eliminate possible damage to your transmission, your odometer will not unnecessarily increase.
The smart is rear-wheel drive. In the event a tow truck is necessary, the smart can be towed from the front, rear wheels on the ground, for a short distance (suggested 30 miles maximum). Be sure the vehicle is in N (Neutral) and the parking brake OFF.