PUZZLE 074 Traffic Jam

Here is a tale of a road plagued by traffic jams.
The road has two lanes, and is quite narrow so two cars can only just drive alongside each other.
If the road is jammed up for an hour, there are 100 cars in the queue, and if it's jammed up for two hours, there are 200.
If the only possible cause of the traffic jam is cars, what would be the minimum number of cars that could cause a three-hour delay?

Hint 1

Read the problem carefully, and make sure you know what the question is.
You're not being asked the number of cars in the jam.

Hint 2

How many cars would it take to cause a jam?
That's what you need to figure out.

Hint 3

The road is narrow, so if the first car was blocking the road, that would cause a jam.

Super Hint

Continuing on from hint three...
It's a two-lane road, but imagine what would happen if the first car was stopped sideways on.

Answer for 'Traffic Jam'

The answer is '1'.