Limit the horsepower and top speeds of cars?

This interesting and courageous post was made by "xrunner2" in one of the http://www.edmunds.com/ forums on General Motors this past Monday:

“GM could take the lead in manufacturing and marketing sensible sized and powered cars and suvs. They could pronounce that they are doing their part to help US cut down on use and need for foreign oil by biasing future production of vehicles toward smaller, more efficient designs that need less fuel. They could also claim that they are doing their part as a responsible US company to help cut down on highway crashes (not accidents) by not putting high-powered or fast vehicles into the hands of immature drivers (which could be earth aged 16-80).

“Except for police cars they supply, they could even plan to build all of their vehicles say 5-10 years out that do not exceed 80 MPH and are totally tamper proof from those wanting to increase HP and or speed potential of vehicle. Can anybody justify the need or reason to go faster than 80 MPH? Can anybody justify having a car (3000-4000 lbs as example) with 300, 400, 500, 600 HP? Analogy of needing a 600 HP car is same as a whacko gun owner/collector claiming he needs a machine gun/gattling gun rather than a handgun only to protect his house and family from intruders.

“Now this would truly take great leadership. Does GM high management have the ability to take these steps? I believe that the vast majority of responsible driving Americans would agree with GM for making a commitment to sensible sized and powered vehicles. Other mfrs, Ford, Chrysler, Toyota would then do likewise."

I'd have to say I agree with xrunner2. Why do we need cars with such high-speed capabilities when the highest speed limit in the US is 80 mph? Even on the fabled German autobahn, which has no posted speed limits on certain sections for passenger vehicles, the recommended speed limit is 130 km/h, or 81 mph.

Interestingly, the US government proposed a maximum top speed for cars of 85 mph around 1970-71 (under the Republican Nixon administration). But this trial balloon was quickly shot down by the enthusiast media and their supporters.

Today, such a proposal still wouldn't get very far. But it makes so much sense in my opinion. I realize that making something truly "tamper proof" isn't possible. Still, a lot of high speed "flings" would be avoided with their attendant high risk for death and injury, AND carbon dioxide emissions would be lowered because fuel consumption rapidly increases at very high speeds.