When were seatbelts legally required in back seats?

[Battlewagon3]

Hello.  I'm working on a short blurb about an older car with advanced safety features for its day, and I'm trying to determine when backseat seatbelts were required in the United States.  I'm not talking about "seatbelt laws" requiring people to wear them, but the requirement that they be included on new cars as OEM.  I know that they were required in the front seat from 1968 (according to AAA's website, although I thought it was longer ago), but I know that by the 1970's most American cars (and foreign cars sold in the United States) had backseat seatbelts.  Some of the information I've found online has been incomplete or arguably wrong, but the main problem seems to be that every web search turns up information on "seatbelt laws" rather than requirements for manufacturers.  Does anyone know when backseat seltbelts became required OEM in the United States?  Thanks. 

[rocketraider]

January 1, 1968.

 

That's when USC Title 49, Chapter 301 MVSS took effect. One requirement was seat belts in ALL designated passenger seating positions except on buses, and outboard front seat shoulder belts.

 

Starting around 1963 most American carmakers included front seat belts with rear belts optional, and the cars came with provision to install them. Meaning the anchor points were engineered into the car bodies. Most makes also offered a choice of standard or deluxe trim belts.

 

Starting 1966 General Motors offered shoulder belts as extra-cost optional equipment. The vehicle's body data plate had a punchout that indicated whether the car had anchor plates along the roofrail to attach the belts.

 

I'm leery of installing belts in an older car that doesn't have belt anchor points engineered into the floor pan or body. Unless the anchor points are reinforced to prevent the belt attaching hardware from pulling thru the sheetmetal (or worse, wooden floor) in a crash, belts are for all practical purposes useless in such a situation. Just as bad as no restraint at all.

[Frank DuVal]

1966 was the year GM put rear seat belts in cars as standard equipment. Also back up lamps and outside rear view mirrors.  Maybe in response to knowing the National Traffic and Motor Vehicle Safety Act was in the making, passed in June 1966 (almost a year after the 66 models were first assembled and sold).

 

Virginia State Safety Inspection Rules agree with Glenn:

 

Reject if:

 

4. Any passenger car manufactured on or after January 1, 1968, is not equipped with lap/shoulder or harness seat belt assemblies located at the front outboard designated seating positions (except in convertibles) and lap seat belt assemblies located at all other designated seating positions.

 

[Leif in Calif]

On 12/10/2023 at 10:22 AM, rocketraider said:

January 1, 1968.

 

That's when USC Title 49, Chapter 301 MVSS took effect. One requirement was seat belts in ALL designated passenger seating positions except on buses, and outboard front seat shoulder belts.

 

Starting around 1963 most American carmakers included front seat belts with rear belts optional, and the cars came with provision to install them. Meaning the anchor points were engineered into the car bodies. Most makes also offered a choice of standard or deluxe trim belts.

 

Starting 1966 General Motors offered shoulder belts as extra-cost optional equipment. The vehicle's body data plate had a punchout that indicated whether the car had anchor plates along the roofrail to attach the belts.

 

I'm leery of installing belts in an older car that doesn't have belt anchor points engineered into the floor pan or body. Unless the anchor points are reinforced to prevent the belt attaching hardware from pulling thru the sheetmetal (or worse, wooden floor) in a crash, belts are for all practical purposes useless in such a situation. Just as bad as no restraint at all.

You really need to do a little heavy duty engineering on the belt anchor points.  The stress on them in a collision is several thousand pounds. 

[joe_padavano]

19 hours ago, Leif in Calif said:

You really need to do a little heavy duty engineering on the belt anchor points.  The stress on them in a collision is several thousand pounds. 

This is not rocket science (and yes I am a rocket scientist - or more accurately an aerospace engineer). Seat belt bolts are typically 5/8" or 3/4" grade 8 bolts. Even the crappiest grade 2 1/4-20 bolt has a minimum tensile strength of 2350 lbs. A 5/8-18 grade 8 bolt has over 38,000 lbs minimum tensile load. Factory seat belt hard points are typically mounted through the floorpan reinforcements, which provide plenty of bearing strength in the floorpan. While this is preferable, if mounting through existing reinforcements is not possible, there are commercially available reinforcing plates that perform the same function. And yes, if the load is high enough, the floorpan will yield locally around the reinforcing plate. That's a GOOD thing, since yielding the floorpan absorbs some of the load, reducing the shock to your body when you hit the belt.

 

[Su8overdrive]

Joe, good points and explanation.  We did much of what you outline above in various '40s Packards, 1936-37 Cords, '41 Cad conv., '41 Lincoln Continental, etc.   As we see, some guys would rather parse and equivocate than buckle up.  My uncle raced an Allard J2, '53 XK-120, big Healey and Alva Courier formula car back in the '50s, early '60s.  All had belts, as did his regular car during the "run what you brung" days.    Thank you, sir.   BTW, my late uncle was a Grumman Aerospace rocket tech (Thor, Atlas Agena, Titan I, II, III, Saturn I, IB, V at the Cape whose young artist wife, two small boys and day job prevented him from turning pro racer.  Jake had a sea of trophies.

Edited Monday at 07:03 PM by Su8overdrive (see edit history)