- It appears to me (perhaps incorrectly) that if a small sedan hits a parked small sedan at 50mph, each car will incur damage that is roughly equivalent to a small sedan hitting a brick wall at 25mph.
A: If both vehicles are near the same weight, if it is a central collision (not offset) and if no significant other things happen (other parked cars, a wall, etc.) then yes, the vehicle travelling 50 MPH into a similar parked vehicle will bring the parked vehicle up to approx. 25 MPH while reducing its speed to 25 MPH. It would be roughly equivalent to the car simply running into a wall at 25 mph.
Restitution of the vehicle structures, tire forces and other things are why it is only 'roughly' equivalent.
Equations from our book McHenry Accident Reconstruction (which is currently out of print) which govern the impact are as follows:
