[skzv]

Consider this: would you rather drive head-on into a parked car at 100mph or a brick wall?

[s1artibartfast]

obviously the parked car, but this is an entirely different question.

The parked car will move away, providing cushion.

When you have two cars in opposite directions, they cant both give way for each other.

[skzv]

You could secure the parked car so that it doesn't move, and its crumple zone will still slow the deceleration.