Here at AutoblogGreen we get plenty of questions from readers about all kinds of topics related to alternative transportation. Reader James asks: "Reportedly, there is a federal law which limits the size/speed of autos on all roads. This, in effect restricts electric alternative vehicles that must exceed 35 mph speed. I haven't got the whole story correct, I'm sure. That's why I'm trying to get the straight story. Specifically, determine whether such a Federal law exists, and if so, what exactly does it restrict?" So what exactly is the story?

In the electric "car" ranks there are basically three classes of vehicle. There are three wheelers like the Zap Xebra or Aptera which are classed as motorcycles and therefore not subject to crash safety standards. These vehicles are allowed to operate at any speed. Then there are full-speed vehicles which have at least four wheels, are capable of exceeding 25 mph and have a gross vehicle weight rating of less than 8,500 lbs. These vehicles are subject to all of the same safety regulations as any other car on the road today. That means the bumpers must withstand 2.5 mph impacts, there must be seatbelts and airbags and all sorts of other rules regarding lighting and impact safety are enforced. The only series production EV currently available in the U.S. today that meets this classification is the Tesla Roadster. Then there are low-speed vehicles. Read on after the jump to find out more.

The rules governing low speed vehicles are not specific to electric or any other type of drivetrain. You could have a gas- or diesel-powered low speed vehicle and it would have to meet the same requirements. To qualify in this category, a vehicle must have a top speed greater than 20 mph but not more than 25 mph. Anything that can only go less than 20 mph is not covered. Battery powered low-speed vehicles are also often referred to as neighborhood electric vehicles. It's important to note that these rules are based purely on vehicle capability and do not in anyway discriminate based on the type of powertrain.

The National Highway Traffic Safety Administration had this to say about low-speed vehicles: "The agency notes that the growing on-road use of golf cars has already resulted in some deaths and serious injuries, and believes that the new standard is needed to address the effects in crashes of the higher speed of low-speed vehicles. The standard requires low-speed vehicles to be equipped with headlamps, stop lamps, turn signal lamps, taillamps, reflex reflectors, parking brakes, rearview mirrors, windshields, seat belts, and vehicle identification numbers. The agency believes that these requirements appropriately address the safety of low-speed vehicle occupants and other roadway users, given the sub-25 mph speed capability of these vehicles and the controlled environments in which they operate."

Essentially, if someone wants to operate what is basically a golf cart on public roads, it must have some basic safety equipment in place as defined by Federal Motor Vehicle Safety Standard 500. Generally, these 25 mph vehicles are allowed to run on public roads with speed limits up to 35 mph. On roads with speed limits greater than that, they would pose too much of a safety hazard both in terms of holding up traffic and, since they don't have the structure required to withstand impacts at those speeds, to the occupants.

Full-speed vehicles are subject to dozens of federal and state regulations and, again, the rules apply regardless of the powertrain type. Full-speed EVs are, at this point, much more expensive than NEVs due to battery costs and other issues. Low-speed vehicles have far fewer requirements and thus can be built at much lower cost. They are certainly useful for certain limited applications, but won't meet most drivers needs.

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