I investigated the new style crash barriers in the summer and learned that they had replaced this type. These ones have the end bent down into the ground to stop the end piercing the body of the car in the collision. The problem with this design turned out to be that it added a vertical component to the force applied to the car because the normal contact force is pointing up an angle 90 degrees to the inclined surface of the barrier. This will cause a vertical component to the resultant force on the car, thus an upward acceleration and it will make a car flip if the car hits at the wrong angle.
