text: Every accident is a little different, but in theory, a few principles apply:\n\n1) The higher the combined speed of the vehicles, the greater the risk.\n2) The greater the "acceleration" (meaning rate of change in velocity, and includes "deceleration") of a vehicle, the more damage.\n3) The heavier vehicle or the one traveling faster will usually have an advantage.\n\nNow, we can analyze those principles further.  Point #1 combines the vehicle speeds (velocities).  If the vehicles are travelling in exactly opposite directions, this will be at the maximum of simply totalling the two vehicles' individual speeds.  If they are at any other tangent to each other, the math is a little trickier, but it won't be at the maximum when combined.  Point #2 shows that it is the _change_ in speed that causes damage.  From this principle, I would far rather not "bounce back," as this means I would have changed speed all the more.  To simply stop, means I have gone from, say, 60 to 0, or changed 60 mph.  To bounce back means I have gone from 60 to -20, or changed 80 mph (not necessarily those numbers, but you get the idea).  Point #3 is true because the heavier and/or faster vehicle will usually keep going, forcing the slower/lighter vehicle to reverse direction.  Therefore, one vehicle might go 60 to 10 mph (change  of 50) while the other went from 55 to -15 (change of 70).  Having said that, it would be pure foolishness to increase your speed before the accident, owing to principles #1 and #2.