Twice the crumple zone divided by two cars is the same as one car and one crumple zone.
Twice the crumple zone divided by two cars is the same as one car and one crumple zone.
The parked car will move away, providing cushion.
When you have two cars in opposite directions, they cant both give way for each other.
The trampoline doesn't deflect, and acts exactly like a concrete wall.
The trampoline cant simultaneously deflect in opposite directions.
Same amount of momentum, two collisions. In one, there is one crumple zone, we will assume the brick wall is completely undamaged, for the sake of simplicity. In the other, there are two crumple zones.
All of the crumpling is dissipated energy. What doesn't get crumpled, goes into the driver's face.
Clearly, the situation with two crumple zones is superior. There's a limit to how much energy can be absorbed by crumpling. With two crumple zones, that limit is 2x, with one, 1x.
Therefore, damage to the driver or drivers is much worse in the brick wall scenario.
For another analogy, picture a go-kart, with a half-meter block of styrofoam, hitting a brick wall. Now, picture the same go-kart, hitting at the same speed, but this time, there's a meter of styrofoam.
That's the one-crumple and two-crumple scenarios.