I asked a very similar question a couple of days ago.
The answer is ,like Bunji said, that in most cases they actually do race. So Jeremy probably was flying down the autobahn.
After the race the crew go back and fill in the gaps with footage of them driving the car from the outside and with scenery.
I was a bit sceptical for a while as well, but this info resolved that for me. Hopefully it does for you too.
"Oh I'm sorry, were you addressing me? Because your authority is not recognised in ... Fort Kickass"