+ BIG 1.

 

Studies like this are so obvious, and so misleading, that they drive me crazy. The assumption is that all cars get into accidents at equal rates, that accidents will happen equally across the board regardless of what you're driving. So, the bigger the better, right?

Well, in that case, it's an arms race and the winner will be driving an M1 tank. Armor up! It's just insane that no consideration is given to the ability of a car to avoid an accident, to reason that if a car handles well, stops well, and accelerates well it can avoid an accident that will ensnare a fat, heavy, bloated, SUV with crappy brakes and a center of gravity slightly higher than Mt. Everest.

My 16-year-old daughter drives the Cooper and although I worry about her of course, the fact that she's driving a car that has accident-avoidance capabilities makes me feel better than if she were driving a Hummer.

 

If you look at my gallery you will see damage to my mini after a 35MPH rear end wreck. The other car was a Toyota something, cant remember.

 

No its four times. A 40 mph head on collision with an object travelling 40 mph toward you is the same as an 80 mph collision with a stationary object. Hence your total energy in both cases is:

1/2m(80)^2 = 3200m (40 mph head on with object travelling 40mph)
1/2m(40)^2= 800m (40 mph with stationary object)

Your energy is thus 3200m/800m = 4 times larger.

 

No - in the two-car scenario, you don't get to add the two "40 MPH" figures together and call it "80 MPH". Kinetic energy is a property of individual objects, and is not dependent on the object's speed relative to some other object.

You have to add up the individual kinetic energies like I did in my previous post:

So, to use your numbers (even though the units aren't correct):

1/2m(40)^2 + 1/2m(40)^2 = 1600m (two cars, each traveling 40 MPH)
1/2m(40)^2 + zero = 800m (one car at 40MPH hitting a stationary object)

The difference in total energy between the two scenarios is a factor of two, not four.

 

Bottom line - it's not just the "amount of force" that matters... it's also a question of "what does the car do with that force" and "can't we just avoid the force in the first place?".

Don't use the force, Luke.

 

Good point - it's also worth realizing that in a crash, your chances of fatal injury are proportional to your change in velocity (which includes direction as well as speed) during the collision. This also takes into account safety features like crumple zones, since those will reduce your change in velocity during a crash.

Here's the video of the Mercedes/Smart crash:


If you look at the Mercedes, it continued moving forward even after the cars separated, so its change in velocity during the crash was less than 40 MPH.

The Smart, on the other hand, went from traveling 40 MPH forward to being knocked backward at an angle, so its total change in velocity during the collision was actually greater than 40 MPH.

 

My friend Billy drives a big SAFE Ford Explorer. Billy gets 17 MPG TOPS on the freeway. I drive an O7 MCS and I just got 37.7 mpg (4.8 gals over 181 miles) doing open backroad and freeway driving...and a lot of it was at 70+ mph. Even in full time in town heavy stop and go driving I always break 30 mpg I consider the MCS to be a performance car, not an economy car, so by my reckoning, this car is pretty cool. 11k miles on it now, trouble free. Just drive with the attitude of a motorcycle rider...as if you are invisible. Defensive driving beats a lah tee dah attitude while driving an oversized SUV tank, imo.