30MPH/20G Testing: It’s Not JustThe Speed, But The Force That Matters

INDUSTRY NEWSMay 2, 2011

At the University of Michigan, an impact sled ‘rebounds’ to create a 30-mph change in velocity to simulate a severe frontal crash. With the Q’Straint Wheelchair Securements intact and still functional at the completion of this test, it’s yet another success to add to our extensive list. And while 30 mph might sound slower than a Sunday drive with the grandparents; the reality is that this 30 mph / 20 G test is more severe than it seems.

Even with vehicles traveling at high speeds, statistics tell us that a 30 mph (48 kph) change in speed during a frontal crash is more severe than 95% of all accidents. A myriad of engineered crumple zones, impact absorbing elements and other vehicle components also lie between the occupant and the incoming object. So forces in a 30 mph crash would therefore be lessened in the real world, especially with larger vehicles. However, the sled and surrogate wheelchair used in this test are made of rigid steel and absorb virtually none of the impact, which is a fancy way of saying that the full effect of the impact is felt on our tiedowns.

The equally important (and often over-looked) measurement of this standard are the G forces. Had most of us paid attention during physics class; we might remember that 1 G is basically the mass of an object at sea level. To comply with the testing standard, the crash test must register 20 G at the sled level, which increases the mass of the rigid surrogate chair and crash-test dummy by more than 20 times. Higher up, away from the platform toward the dummy’s head, more G forces can be registered (50+). Even in serious car crashes, forces such as these are extremely rare.

So, if you happen to hear about a 30 mph / 20 G crash test, don’t think it’s too slow to make you feel good about your wheelchair securement system. Always demand updated crash testing from your wheelchair securement manufacturer. And remember, it’s not just the speed of the 30, it’s also the force of the 20 that can give you peace of mind.