If they're going the speed limit or even less depending on conditions, you have no grounds to complain. Besides, it won't be long before self driving cars are on the street in which case, more and more cars will drive the speed limit. The going 5 to 7 mph above the speed limit will eventually fall by the wayside and quite frankly, even with just cruise control, it should. If someone does the racing thing to block the lanes on you, that's because they think you're driving like an *sshole and they want to p*ss you off.

Of course - California doesn't need ANY of the revenue produced by fuel powered cars and the drivers thereof- they can make fisical ends meet through karma, and crystal therapy and other forms of natural financial profits.

Taxes - can you spell taxes - Fueled cars will be taxed into oblivion by obliviots.

At 30 mph, the first mile takes 2 minutes.
At 60 mph, the second mile takes 1 minute.
The total 2 miles took 3 minutes averaged together.
To convert minutes to hours you multiply the 3 by 20 to get 60 minutes in an hour.
So the average is 2 times 20, or 40 mph.

If you wonder why it is not half way between 30 and 60, which would be 45, that is because you did not spend as much time at 60 mph as you did at 30 mph, so the average is lower than what one might first guess.

Whereabouts in Kent exactly?

Dungeness is in Kent. So is Ramsgate. And Dartford. The traffic going into London on a Saturday morning (or any other time of day / week) will be totally different from each location. Especially when you consider that Dartford is actually inside the M25 anyway...