Here's the story from AutoBlogGreen.com:
Towing a vehicle, especially one that's powered by batteries and driven by an electric motor, can, if done incorrectly, be destructive. Recently, one of Frito-Lay's electric Smith Newton delivery trucks was towed for a parking violation and, according to Green Car Advisor, was reclaimed by Frito Lay employees who arrived with a flatbed tow truck. Well, as GCA's Robert Calem points out, it's unusual to witness an impounded vehicle towed, rather than driven, off the lot.
This oddity drove GCA to dig deeper and reach out to Bryan Hansel, chief executive officer of Smith Electric Vehicles, for an explanation. The Newton has no transmission connecting its electric motor to the rear drive wheels. Furthermore, the Newton is not equipped with a "neutral" selector to disengage the wheels from the motor. Therefore, towing the Newton with its rear wheels on the ground would force the electric motor to spin. However, since the delivery truck's liquid cooling system is inactive when the vehicle is off, excessive heat could build up and destroy the motor.
Hansel told GCA that the proper way to tow a Newton is to either drop the driveshaft, which connects the electric motor to the rear wheels, or to lift it from behind with the front wheels on the ground. Obviously, tow truck drivers are unlikely to spend half an hour pulling a driveshaft, so Hansel simply advises that Newtons either be hauled away on a flatbed or not towed at all.
Many battery-powered vehicles, including the Nissan Leaf and Ford Transit Connect, are engineered in such a way as to eliminate potential towing issues. However, the use of flatbed tow trucks nearly guarantees that hauling away a plug-in vehicle will not be a motor-destroying event.