Critique of the Transport Canada Tests

Arthur L. Yeager, DDS
Chairman, NCSSB
May, 1985

The January 1985 Transport Canada report of school bus crash tests has been widely publicized as proving that seat belts could not be used on the large (Type 1) school bus and that the so-called "compartmentalized" school bus seat without a seat belt offers better protection for children. Nothing could be further from the truth.

In the Canadian tests a large, a mid-size and a van type bus were subjected to severe 30 mph front end barrier crashes. On each bus there were six 5th percentile adult female anthropometric dummies, three belted and three unrestrained. From previous studies at UCLA and at East Liberty, Ohio it was learned that in such high force front end crashes belted dummies tend to pivot over their seat belts and strike their foreheads on the padded seat backs in front of them. Unbelted dummies on the other hand are thrown forward violently by the crash forces into the seat backs which they face. When measuring devices are placed by the researchers in the head and chest of these dummies, the belted dummies produce higher head readings and the unbelted higher chest readings. Experimentally, Head Injury Criteria (HIC) levels of greater than 1000 and Chest Accelerations of greater than 60g. are generally accepted as sufficient to produce severe injury or death.

The results of the Canadian test of the large bus are below. In this test crash of a 66 passenger bus the only dummy experiencing life threatening forces was dummy no. 1 seated unbelted in the front left hand seat with a chest reading of 60.4g. All belted dummies were well within acceptable limits. The bus met all current federal standards including Standard 222 for school buses.

Since it is well known that the Federal 222 seat offers no protection at all for passengers in side impact and no "whip lash" protection for taller riders in rear-end crashes, and that the seat was developed primarily to protect against injury in front end crashes, the failure to protect dummy no. 1 without a seat belt is of particular concern.

In this type of front end test crash, as explained above, belted dummies will produce somewhat higher HIC levels than the unbelted dummies. In addition, the selection of the 5th percentile female which is just the right height to target the dummie's head to the area of the seat back where the padding narrowly covers the metal bars of the seat and the use of the type 572 dummy which has been widely criticized for excessive HIC readings in crash tests severely prejudices these tests against seat belt use. In spite of all these test induced disadvantages, the dummies with the seat belts on the Bluebird bus did remarkably well. On the other hand, in spite of the large area of the seat back to spread the forces, in spite of the large area of the seat back to spread the forces, the unbelted dummy in the front seat would have experienced serious or fatal injury.

When film of the crash is viewed, dummy no.4, unbelted in the center seat, is seen to fly forward until its throat strikes the top of the seat back. In a high force frontal crash such as this the resulting throat injury would have been severe or fatal. It is conceivable that the HIC and chest readings were lower on this passenger because the throat and neck absorbed so much of the crash energy. Just how much force was so absorbed was not determined because, unfortunately, the researchers decided not to instrument the necks of the dummies.