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Windshield cracks and occupant safety

Windshield cracks and occupant safety — is driving with a cracked windshield a safety risk?

The windshield is a structural component of your vehicle

Many glass companies state that the windshield provides up to 60% of the strength of your roof and pillars in a rollover. I haven’t been able to find any scientific data to support that claim. However, there are scientific studies to support the fact that the windshield is indeed a structural component. Here just a few citations.

The Federal Motor Vehicle Safety Standards (FMVSS) are U.S. federal vehicle regulations specifying design, construction, performance, and durability requirements for motor vehicles and regulated automobile safety-related components, systems, and design features.

FMVSS 216 covers Federal roof crush standards

PROTECTION by Donald Friedman MCR/LRI, Inc. and Carl E. Nash, Ph.D
The George Washington University United States Paper No. 01-S12-W-94, the authors state the following:

” Almost all light motor vehicles on Americanroads meet FMVSS 216. It requires that a roof withstand a force of up to 1½ times the weight of the vehicle. For passenger cars, this force is limited to 5,000 pounds. The force is applied at a 5° pitch and 25° roll angle over where the A-pillar meets the roof panel. The vehicle passes if the roof deforms less than 5 inches when the maximum force is applied.

The steel structure of most modern vehicle roofs and supporting pillars, weighs less than 3 percent of a vehicle’s curb weight (the steel in a car roof typically weighs less than 100 pounds). When tested under FMVSS 216, more than 30% of a roof’s static strength may come from its bonded windshield. That is, many modern vehicles could not meet FMVSS 216, if their windshields were removed.

Dynamic roof loading in rollover almost always fractures or separates the windshield from its frame when the roof first contacts the ground. Without the
strength provided by its windshield, the roof is much more likely to deform and buckle upon its subsequent impact with the ground.”

Another scientific paper: International Conference on Industrial Engineering, ICIE 2016 Car Windshield Protection A.S. Pereverzev*, B.A. Semenikhin South-west State University, 50 years of October Str., 305040, Kursk, Russia states:

The windshield is an integral part of the vehicle structure. Due to its design and location, the windshield is exposed to a wide variety of loads: wind load, load due to the elastic deformation of the car body, as well as the impact load by roadside stones

The windshield is a critical component in the safe operation or your airbags

Airbags, especially passengers airbags are designed to deflect off the windshield during deployment and inflate toward the passenger. If the windshield is compromised by cracks, it can shatter during deployment, in which case the airbag would not properly deflect toward the passenger, negating is ability to protect the passenger. In fact, the passenger airbag can inflate outward, through the open windshield providing no crash protection whatsoever.

The windshield is a critical component for the proper operation of Advanced Driver Assistance systems (ADAS)

The windshield mounted ADAS cameras rely on a distortion free windshield to provide proper collision avoidance operation. Cracks in the windshield, even if they’re not directly in front of the camera, can cause optical distortion to the cameras.

Windshield cracks in the exterior portion of the laminate can allow the windshield to flex slightly in turns and with wind velocity. That can cause the collision avoidance systems to fail to deploy, deploy too early, or too late.

Fixing a cracked windshield is critical to passenger safety

A cracked windshield will fail to provide the designed roof support in a roll-over event.

A cracked windshield will fail to assist in the safe deployment of the passenger airbag.

A cracked windshield degrades the effectiveness of ADAS collision avoidance systems.

©, Rick Muscoplat


Posted on by Rick Muscoplat


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