Mr. Chris Davies:

Car manufacturers today rely more on glass as a structural part of a vehicle. That glass, and not only bigger pieces of glass, is one of the main drivers in terms of safety and the environment. From a safety point of view, bigger pieces of glass give better visibility for the driver. From an environmental point of view, using glass, which is a strong material, allows for less metal or steel in the vehicle and brings down weight. Manufacturers rely on the glass to give some level of roof crash resistance in the event of a roll-over, for example, but also it imparts some torsional rigidity; without the glass the vehicle does not drive straight. The wheels are not necessarily parallel and do not necessarily sit flat on the road, and the glass, with the bond and adhesive used, ensures that the stiffness of the vehicle is retained.

The other opportunity glass provides is that it allows for the airbag to inflate properly, particularly for the passenger side, because the steering wheel is in front of the driver and when the airbag inflates it closes a gap. In the event of an accident, the driver is moving forward, the air bag fills that space and provides a cushioning to slow down the acceleration experienced by the body. The passenger does not have close proximity to anything, so he or she relies on a very big airbag to fill the space, and to inflate properly that airbag relies on the windscreen being bonded properly into the vehicle. If the glass is not bonded properly it does not allow the occupant to strike the airbag in the correct position, and the acceleration process is modified greatly.

The final point about the importance of a windscreen in keeping the occupants within the vehicle is that there is a good deal of historic research which shows that if someone is ejected from the vehicle in the event of an accident, his or her risk of significant injury or fatality is increased three- or fourfold. Seat belts help to keep occupants within the vehicle but the airbag has a part to play. If a person is not wearing a seat belt and the windscreen is not there, occupants are not kept within the vehicle. I will show the members some images of what a correctly fitted screen should do in an accident.

One can see the airbag has inflated within the vehicle, thus restraining the occupant, or, rather, controlling the acceleration from full speed down to zero over a controlled period. The airbag relies on the windscreen to allow it to inflate properly. When the passenger strikes the airbag, the cushioning effect is the result of a combination of the positioning of the airbag and the windscreen.

We did some crash tests some time ago to consider the effects of an incorrectly bonded windscreen. We used two Ford Focus vehicles in order that they would behave in the same way. One had correct bonding and the other did not. In the test the vehicles were both travelling at the same speed. One may think of the process as symmetrical; in other words, both vehicles should behave in exactly the same way. One can see the correctly bonded windscreen bulged out because the airbag was doing its job by pushing against it. The energy of the occupant was arrested by the airbag-glass combination. In the other vehicle the incorrectly bonded windscreen became detached and the airbag, the great volume of which should be contained within the vehicle, was partially pushed out of the vehicle. Thus, the occupant could not experience acceleration in the same way. Not only would the occupant hit the airbag in the wrong position but he or she would be subject to a different level of travel. There is a risk that his or her acceleration would be affected more by the seatbelt, which is dangerous, than by the airbag. An airbag acts a cushion, whereas a seatbelt exerts a restrictive force whcih is relayed to internal organs and the bone structure of the occupant.

There is a hidden problem, an invisible problem. The adhesives used in the fitting of windscreens are very sticky. When the job is first done, it looks normal and perfect. However, as the polyurethane adhesive cures, it becomes hard. Since the chemistry of polyurethane is different from that of typical paints on cars and glass, the adhesive comes away from the glass or body work over time. This leads to two scenarios. Either we notice a damaged windscreen is not stuck in properly when we go to replace it or, worse, we notice the windscreen actually comes out in an accident, potentially resulting in greater injury. The chemistry of the adhesives is complex. There are primers and the adhesive. They are designed to ensure the windscreen remains in the vehicle during a severe accident. As members will have seen in the image of the crash test, when a windscreen behaves properly, although the glass fractures, it remains entirely in the car and allows the airbag to work properly.

Our technicians get very concerned about windscreen bonding when removing windscreens. The image shows that adhesive that should be intimately bonded to the vehicle can be pulled away by hand. This should never happen. In the image of the Garda van, one can see that the windscreen is capable of being pushed out by hand. The image of the customer vehicle implies that the windscreen should be intimately bonded to the vehicle such that it should stay in place in an accident. This is clearly not the case with the vehicles in question.