Right, the end-handling of blocking the intersection is different by necessity (just imagine beyond the end is a cliff that cars fall off so the exit from the intersection is never blocked!). Anyway, the rules for those scenarios are covered by the spec:

• It is illegal to queue across an intersection. In other words, DO NOT enter an intersection unless you can see there is safe passage through it and out the other side!
• If there is a traffic light at the end of the road then its exit is never blocked

Which rules seem counter-intuitive?

I feel your pain. But it kinda does -- the Description says that it uses x for rows and y for columns. It's messed up, but it is specified.

I would gladly disable gmp library for python but from previous experience this provokes a lot of nagging.

The tests are fine, your function's name is formatDuration instead of format_duration. Rename it so the tests find it.