Carl F. Thelin

 WINDOW SHADE TENSION-RELIVER

Back when the auto industry introduced the tension reliever, I was writing for Consumer Reports. GM will always comment that, when I was writing about auto safety, I was not consistent in my criticism of seat belts.

The TENSION RELIEVER system uses retractors that lock only when a vehicle stops abruptly (as in a crash or panic stop) or turns sharply. In addition, a ratchet mechanism relieves the tension of the shoulder belt when the occupant slowly leans forward and back. So far, so good. But occasionally that arrangement can be fooled, creating excessive slack in the shoulder strap when the occupant moves about - the reach the radio, for example. To take up the slack, one must quickly move forward and back (something like tugging on a window shade to raise it).      

April 1976 page 209, I said:

“The new Chevette had the new window shade system:

"Safety Features: Each front safety belt has a single length of webbing that runs through the tang (the male end of the buckle) to form both the shoulder and lap straps. Most such restraint systems let the webbing slip freely through the tang, that could allow dangerous 'submarining ‘‑ in which the occupant slides downward and forward in a crash ‑ if the belt is worn too loosely. In the Chevette's system, the webbing does not move freely through the tang, thus preventing submarining.

That isn’t the major problem with the system. Opening the car door also releases the ratchet and allows the belt to retract, but the retractor often needed help in winding all the webbing back into place, a nuisance that could discourage use of the belts. The lap belts tended to ride a bit high rather than remaining low on the hips, as they should.”

I am unhappy about the “Dick and Jane” way I wrote this, and about the substitution of the word tang for latch plate. That year - 1976 - I wrote other things of interest. No domestic vehicles were in the January issue.

In February, page 89, Mid-Sized Cars:

Chevrolet Chevelle:

“Safety features: The front belts were easy to put on. The shoulder-strap tension was pleasantly low.”

AMC Matador:

“Safety features: ...The tension of the shoulder belts was uncomfortably high. ....”

Ford Torino:

“Safety features: The tension of the shoulder belts was uncomfortably high - a common problem with Fords.”

In February, we had already purchased all the cars for the first five months the autumn before, and knew what other Fords were like.

….

In March, page 160, Economy Compacts

Chevrolet Nova:

“Safety features: The front safety belts were comfortable ...”

Ford Maverick:

“Safety features: Tension of the shoulder belts is uncomfortably high unless one adjusts the comfort clips.”

([Manual comfort clips were outlawed later.)

I already covered the April issue, where we reported on the new Chevette.

May 1976 page 262, Luxury Compacts.

Dodge Aspen SE:

“Safety features: ... The retractor for the upper portion has a ‘window shade’ mechanism to relieve tension on the chest. ...”

Ford Granada Ghia:

“Safety features: The front safety belts appear well designed: the lap portions remain low on the pelvis, where they can give the best protection in a crash. ...” [No window shade]

Pontiac Ventura SJ

“Safety features: The front safety belts were comfortable and convenient, but the lap portions rode too high ...”

AMC Pacer D/L:

“Safety features: ... and the shoulder straps tended to slip off the shoulders of some occupants.”

…

Finally, to jump ahead and end these examples.

August, page 445

Cadillac Seville:

“Safety features: ... there is a feature that automatically relieves the tension of the shoulder belts.”

I said nothing about the Mercedes-Benz 280S seat belts in that story. They did not have the window shade tension reliever. I should have praised MB for that.

In the following years, we noted that some cars had shoulder belts with uncomfortable tension. GM notes that our criticism of the excessive slack was applied more often to cars from Ford. That is true; however, there are more lawsuits that involve GM.     

This well-known document demonstrates, in great detail, the danger of using a lap / shoulder belt where the shoulder belt has excess slack so that the user can slip completely out of the torso restraint.

SAFETY STUDY - PERFORMANCE OF LAP BELTS IN 26 FRONTAL COLLISIONS

NTIS document PB86-917006  July 1986

NATIONAL TRANSPORTATION SAFETY BOARD

NTSB/SS-86/03

In the Overview of Findings from Safety Board Crash Investigations:

“Among the 50 persons using a lap-only belt, the Board determined that at least 32 of them would have fared substantially better if they had been wearing a lap/shoulder belt. In many cases, the lap belts induced severe to fatal injuries that probably would not have occurred if the lap belts had not been worn. . . . The injuries characteristically induced by the lap belt were among the most dangerous types of injuries: those to the head, spine and abdomen. “