Over at the Examiner, Mark Tapscot is warning that the EPA is going to inevitably mandate a national speed limit, as a result of its CO2 endangerment finding.
I don't think the EPA will do it, in part because I am not sure they can. The EPA has a mandate to regulate major emitters of pollution, and in general works on the large scale industrial policy level. The EPA makes rules on smog forming automobile emissions, also known as Tier II, for example.
Speed limits are locally regulated, on a state-by-state basis. The old 55mph national speed limit was enacted by Congress, and was enforced on the states with the threat of withholding road funding. The EPA doesn't have this budgetary power, and I am not sure if it has the legal authority to impose a national speed limit.
The EPA could, however, publish a rule that requires automakers to add speed related equipment to their vehicles. For example, a GPS system with a database of local speed limits could babysit the driver and make it unpleasant or impossible to speed. At the most extreme, the EPA could mandate a speed control system which simply limits the top speed of a vehicle.
I think it would be an excellent national debate if they tried for it. Let's get it out in the open. Do we believe in man-made global warming, as a nation, or do we not? Do we buy the EPA's ruling that CO2 is a poison, not just a plant food?