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I've heard radio car commercials and other sources state that a vehicle's windshield provides most of a car's structural integrity.

I believe that the company that owns the commercial is Mark's Mobile Glass, but I'm not 100% sure. I'm also not sure on where to look to find the commercial.

Their web-site gives a slightly different claim:

Q: What can be as important to auto safety as seat belts, air bags and anti-lock brakes?

A: A windshield.

A windshield gives you protection from wind, rain and debris. But did you know that auto glass can save lives by preventing the driver and passengers from being thrown out of a vehicle in a collision?

Wikipedia repeats the main claim with insufficient referencing:

Modern, glued-in windshields contribute to the vehicle's rigidity

[...]

If the adhesive bond fails at any point on the glass it can reduce the effectiveness of the air bag and substantially compromise the structural integrity of the roof.

Is there any evidence that proves or disproves that any conventional car uses the windshield for structural integrity?

  • most protection against frontal colliding objects maybe, I thought it was the roof – ratchet freak Sep 1 '11 at 17:14
  • Are you including Jeeps in the set of "cars"? – mmyers Sep 1 '11 at 17:16
  • As @mmyers mentioned, I don't think the old Jeep cj's with the fold-down windshield really fit the bill – Monkey Tuesday Sep 1 '11 at 17:55
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    It seems unlikely in modern unibody cars. The structural integrity comes from the body itself. And the windshield is not under any load or strain. – Daniel Iankov Sep 1 '11 at 18:24
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    Yes, windshields are the primary structural component. This is why you see all those news stories about cars disintegrating at 70mph because a rock cracked the windshield.... oh wait... perhaps not. – Russell Steen Sep 6 '11 at 17:48
8

According to a 2006 Bloomberg article:

Finally, there is the integrity of the passenger compartment. Years ago, most vehicles had steel A-pillars to support the roof. Today, it is the windshield that provides much of the support that prevents the roofs collapse during vehicle roll-overs.

The Complete Guide to Auto Glass Installation also discusses this issue from a litigation point of view, saying that a California woman became quadriplegic in part due to failed bonding of a windshield, causing roof crushing during rollover of her minivan.

This case was Rhyne v. Windshields America.

Transcript of 25 February 2000 20/20 TV show:

ARNOLD DIAZ (VO) Four years ago—Charles Rhyne had the cracked windshield on the family’s minivan replaced at a local glass shop. Seven months later — on a rainy California highway — the minivan slid off the road, his wife Tracy behind the wheel.

CHARLES RHYNE We were rolling. And when the vehicle stopped, I couldn’t move.

ARNOLD DIAZ (VO) The replacement windshield had popped out during the rollover allowing the roof to buckle into the passenger compartment— breaking Tracy’s neck.

TRACY RHYNE If that windshield had reinforced like it was supposed to-I would have had at least four to six inches clearance.

ARNOLD DIAZ Do you think about that?

TRACY RHYNE All the time.

ARNOLD DIAZ (VO) At first this mother of three didn’t want to believe it when doctors told her the accident had left her a quadriplegic.

TRACY RHYNE When I heard it from Charles, I knew for sure that — that it was true. And I wasn’t going to be able to be the same kind of mommy or wife. My life had totally changed in a matter of a day.

ARNOLD DIAZ (VO) The Rhynes sued the company that had installed the replacement windshield and settled for 2 million dollars.

CHARLES RHYNE They forgot to put a secondary primer in the installation of the windshield. So that the hardening material when they put on the windshield — it didn’t harden.

ARNOLD DIAZ (VO) Experts tell us windshields are often improperly replaced because many technicians are either sloppy or haven’t been trained well enough. So we decided to see for ourselves. We had windshields replaced in three different cities.

...

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    I would like to see a scientific/engineering answer to this, vs glass industry or litigation (they didn't glue it in properly but nothing to say would have made difference, except claims by the glass industry). Similar question on Motor Vehicle Maintenance & Repair : Is it safe to drive with a crack in the windshield?, Answer accepted based on unsupported claim "fact the windscreen is an integral part of the structural strength of the car". C'mon folks, we're supposed to be skeptics here. – Keith McClary Mar 10 '17 at 6:09
  • Assessing engineering or scientific facts from the conclusions of legal cases is extraordinarily dangerous as the legal judgements are, too often, based not on the facts but on the whims of juries and judges. – matt_black Nov 11 '17 at 17:04

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