>Gasoline consumption does, in fact, increase non-linearly with speed at highway speeds. Police departments do have to pay their officers salaries.
Neither of these constitute even a slight approach to a justification for lowering the speed limit to give people more tickets. If someone wants to spend their money on gasoline, that's their prerogative.
Well, in the 70s, it wasn't just their prerogative -- gasoline was in limited supply, so if some jackass burned a gallon extra getting from point A to point B, that's a gallon that someone else couldn't have.
Not that inelastic. The problem was that in the 70s Nixon instituted price controls, so there really wasn't any reduction in gas use as gas became more rare. And there were the sort of huge lines outside gas stations that we're used to thinking only occurred outside Soviet markets.
Nowadays, when the supply of gas goes down a bit the price goes up and people carpool a bit more, don't drive to far away stores when there's a nearby store that's almost as good, and drive a bit more slowley. And it does really bring supply and demand into equilibrium - we didn't see huge lines outside our gas stations when Libya had its civil war.
Demand for gas is indeed fairly inelastic, but that just means that the price swings much farther due to a change in supply than, say, the price of a diamond ring does. It would have to be perfectly inelastic for no adjustment to occur.
Neither of these constitute even a slight approach to a justification for lowering the speed limit to give people more tickets. If someone wants to spend their money on gasoline, that's their prerogative.