Carl F. Thelin

BACK WINDOWS

A trial lawyer in Baton Rouge brought me a simple case. I liked doing this one it because the alleged defect was so clean cut. I already had done a bunch like it with more difficult trial circumstances. This would be a chance to focus on the overall design defect that plagued the entire output of the small truck industry.

John Merryweather, the fellow represented by the lawyer, worked in a touring carnival that had been set up in a large grassy field at near Louisiana, near the Gulf coast. Rain fell for most of the night after the carnival closed, as it often does near the gulf. The field turned into a muddy marsh. The next morning the crews packed the rides and displays to move to the next site. None of the trucks had a sleeper cab because the carnival workers slept and ate in their RVs. John was one of the truck drivers. John and others drove trucks like this to transport the carnival rides and displays in several semi-trailers.

            THE INJURY

This case involved a large tractor-truck with one wide glass rear window at the back of the cab. It was like a pickup truck that did not have an extended cab. John’s truck had fairly new tires with good traction. Another truck and trailer were stuck in the mud. The moving manager asked John to use his truck to help pull the other fellow out. John attached a heavy chain to the fifth wheel of his own truck and walked back through the muck to hook the other end to the front frame of the truck that was stuck. John climbed back in and looked out the rear window as he began pulling on the other truck. It was difficult, even with the stuck truck spinning its own wheels. John used his truck to tug, then he relaxed the tension in the chain and tugged again He was inching the other truck out of the muck. Finally, he jerked on the chain too much. It snapped free of the cross member of the other truck. The recoil of the chain caused the hook at the end to spring back toward John’s truck. The heavy, fist-sized hook crashed through the back window and struck John in the forehead. He had a big muddy dent in his forehead and he was severely injured. I thought, after reading that synopsis of the incident that he was permanently brain-damaged. At the trial, I expected to testify as I had done before in similar cases involving truck back windows. I, and the medical expert, would talk about the cause and effect of a closed head injury that is so common in rear end impacts of cars and trucks without adequate head restraints. He would be mentally handicapped and require support for the remainder of his life, I assumed.

            THE OVERALL ISSUE

In those days (we are talking about the 1990s) before most pickup trucks grew extended cabs or crew cabs, a pickup truck was a small version of John’s truck. In a standard pickup, or a big truck without a sleeper cab, the back of the driver’s seat was always located close to the back window unless the driver was short-legged and pulled the seat way forward.

When this type of truck-back-window case was common, only a few models of imported pickup trucks had head restraints on the front seatbacks. Domestic pickup trucks had short seat backs, so if another vehicle hit the truck from behind, the truck would accelerate forward and the rear window glass would slam into the driver’s head.

Tempered glass is strong and difficult to break unless hit with a sharp, hard object like a hammer. The back of the driver’s head is not that hard. Instead, the driver gets a blunt-force head injury from the window. In the case of Mr. Merryweather, I planned to use the same argument as for those rear impacts. I said it should be obvious that the rear window of a truck so close to the driver’s head should be resistant to penetration. Such a window would be made of two thin sheets of glass which are laminated with soft stretchable plastic, like the windshield of every car and truck

That laminated back window should also minimize crash energy by breaking before it cracks the skull since that is the federal requirement for the windshield. The sheet of glass and plastic would absorb crash energy by pocketing and retaining the impacting object, just as the front windshield does.  To save money, the back window of a pickup truck only needs to be two-ply laminated safety glass with the penetration-resistant plastic surface on the inside. The Feds require the three-ply glass for the windshield to provide resistance to scratching on both sides. Such is not needed for a back window - note how many have frost-reducing grids and or tinted film on them.

On a big commercial truck rear window, the penetration resistance could even be the familiar chicken-wire-reinforced glass often seen in warehouse security doors. That glass breaks easily, and the chicken-wire stretches like loosely woven steel net. We all know that window is very resistant to penetration if the window is securely framed. We can live with this cheaper solution because, in most tractor trailer operation, the driver relies upon his big side mirrors.

            THE TRIAL

Whoops! There was a surprise as I sat in the courtroom waiting for the trial to begin. I had never met the plaintiff but had heard of the terrible deep dent that the flying hook had made in his forehead. Imagine my surprise when a nicely dressed young man came down the courtroom aisle. His attorney introduced John Merryweather. On his forehead was a barely visible scar. He looked healthy, bright and middle-class wealthy. His lawyer said, later, that John had had a lot of pain and suffering during his rehabilitation, but now he was fine and making a better living than he had as a truck driver. So, it turned out that the case was just about the amount of money John would get for his pain and suffering - not for beating up the truck maker or the auto industry.

            WINDSHIELDS

Normally, federal and state governments, world wide, require that only the front window of a vehicle to be made of glass laminated with a plastic inner liner. Many years ago, front windows were made of ordinary glass, like in older homes, which would break into shards like jagged daggers. In a frontal collision, an unrestrained rider in the vehicle flew forward into the windshield. The sharp edges and points of the glass severely gashed his face and head when his head broke partly through the glass, making a deep jagged pocket. Then if the head pokes all the way through the hole, and the wider shoulders do not, that person gets a necklace of jagged glass around his throat. That is really nasty, like being bitten on the neck by a shark.

For a while, in Europe, they thought that the obvious solution to shark’s teeth problem was to use tempered glass for the windshield. That kind of glass is thin and heat-tempered so that the surface is very strong and hard but brittle. The Europeans thought that frontal collision forces would distort the car-body window frame and break the glass into granules, which would fall away like coarse sugar crystals. The occupant would fly through the opening to safety, they thought. Of course, soon the statistics were overwhelming that ejection from the vehicle was far more dangerous than staying inside, as was the case of American cars with laminated glass windshields. This conclusion was so dramatic that the US, and finally everyone, standardized on advanced laminated glass called HPR glass – high penetration resistant. The strong elastic glass liner is very resistant to full penetration of a head. The force from an occupant’s head will break the windshield before it breaks the skull. You see many cars on the road with a big spider web on the windshield as evidence of a moderate frontal collision. To be effective at retaining the occupants in a crash, the windshield must remain secured to the car itself, even when the car-body window frame twists and deforms during a crash. Before HPR glass, when a windshield was made of normal (flat or curved but not HPR) glass, car-makers secured the glass to the car with a molded rubber gasket. The supplier made the rubber with grooves that gripped the outside edges of the glass and the inside metal edges of the window opening.

A car body bends front to rear, and twists side to side while running on roads less smooth than a billiard table. A convertible body, without the stiffness of a metal roof, often cracks the front and back windows just by driving normally on rough roads. The softness of the rubber gasket shields the glass from breakage during the normal twisting forces imposed on the car body. You may have assumed the black rubber surrounding the windshield was there only to keep rain from weeping around the edges. No, it was a good solution for a problem in the old days when many roads were poorly paved.

Nowadays, factories glue the HPR windshields in place with a thick strong black adhesive so that retention is optimum. It is almost impossible to tear the windshield free. You have to cut it away from the frame with a hot wire or sharp knife. There is another benefit to using strong adhesive to secure automobile glass. Today, all cars and smaller trucks have windshields and back windows curved like a portion of a cylinder, which makes them much stiffer than being just plain flat glass. Gluing the windshield and back window in place actually uses the stiffness of glass to make the car body more rigid in twisting. 

            FIXED SIDE AND BACK WINDOWS

            Cars once used laminated glass in side or rear windows that were fixed in place by thick, soft-rubber grommets that protected the easily-cracked glass from car-body twisting. This stuff surrounding the window was unattractive, so an expensive car was enhanced with polished metal overlays. The whole package of rubber and metal trim was heavy. Finally, learning from the experience with the front window, designers switched to thin, lightweight tempered glass bonded into the frames of fixed glass side and back windows. 

            MANY CASES LIKE THIS INVOLVED ROLL DOWN SIDE WINDOWS

Once upon a time, carmakers used old-style flat laminated glass for side roll-down or swing-out windows. The inner and outer layers of laminated windshield glass are the like household window glass which will break easily and produce large jagged points and edges. A roll-up window in a door had the top edge exposed to impact. To reduce the hazard for anyone reaching through the open window, the edges were carefully ground to a shallow radius. That solved one problem but exposed another. The upper edge of the glass was also exposed to the elements – not just water but also to heat and sunlight – ultraviolet radiation. After long exposure, the laminate adhesive would turn milky white.

Another drawback: they are heavier, per square foot, than the surrounding sheet metal.

            SWITCHING TO TEMPERED GLASS SIDE GLAZING

Switching to one-ply hard-tempered glass solved that problem. About that time, almost all side windows had a slight curvature when seen from behind, which made them stiffer, that way, too. The safety argument still rages. Now some engineers ask if laminated glass is better, for side and rear windows, despite its greater weight and cost. I see two benefits. Laminated glass breaks easier when hit by a person’s head, thus reducing the forces applied to the head and laminated glass will serve as a retaining net after being broken. Others argue that the difference in breaking force is not so important. The safety net effect is dependent upon secure attachment of the glass all around its perimeter. That is not easy to achieve with a roll-up window. The upper edge of a side window is not retained when partially lowered. Even when the window rolled is rolled up, friction is all that holds the top and sides of the window in the doorframe slots. Once upon a time, especially on convertibles and hardtops, shiny metal frames surrounded the exposed edge of such windows. That meant more weight so that option is gone.

            HOW ABOUT HALF A SOLUTION?

Windshield glass is a three-ply laminate. The inside and outside layers are un-tempered “float” glass like your home windows. The sandwich layer is soft plastic, which is firmly adhered to the inside of each glass layer. There have been some attempts to use four-ply glass windshields. The fourth layer was another layer of plastic on the inside surface. Its purpose was to prevent the occupant’s head from being lacerated by the broken glass from the inside glass layer. That does work well, of course, but has a serious drawback, especially for a front window. Over the lifetime of a car, the owner needs to clean the windows hundreds of times – inside and out. A squeegee or a rag could easily scratch or gouge a soft plastic inner surface. Hard glass is much more resistant to scratches. That is why ice scrapers are plastic and not steel. Forget about four ply windshields - the law pretty much insists on crystal-clear three-ply HPR. A scratched inside plastic surface of a windshield pretty much ruins the purpose.

People fly or fall out of a side-window opening at the front and rear. I suggest using two-ply glass on the side windows and the back window, too.  We compromise with thin hard, tempered, curved glass with a plastic layer on the inside. It is not so critical if you scratch side and back windows when wiping them down, or scrapping frost. Opponents argue that scratches to the inner surface will build up in time to make the side window less that perfectly clear. Well, so what? Is clear vision, even for the driver, that critical to the sides? If so, why do so many people have their side windows covered with dark tinted plastic. Back windows are tinted, too. True, the stuff put on the windows by after-market installers is not well equipped to function as ejection retention but the principle is the same?

Two other factors support the use of two or 3-ply laminated glass for the sides and back. In Europe and Japan, they advertise this stuff as “theft-resistant” glass. Yes, a thief can break that glass, but he can hardly reach through it to grab you or your possessions. Luxury carmakers advertise laminated side glass as a sound-absorbing selling point feature.      

BACK TO TRUCKS

I started this talking about the back windows of trucks. As I said, in some truck cabs, the driver’s head was so close to the back window that it is dangerous. That threat is gone now because trucks must have head restraints on the front seats now, and some do on the back seats as well. That is one reason the extended cab pickup truck became more popular – it makes more room for a decent front seat with a good-sized head restraint. You even see workmen’s pickup trucks with a metallic screen covering the rear window where the framework is attached to the front edge of the load box. 

Pickup trucks were once a cheaper vehicle than a sedan. MPV – Multi Purpose Vehicle was the initial description given by the National Highway Traffic Safety Administration to a pickup truck - really. There were no luxury features. A pickup (light truck in DOT language) was a vehicle designed to carry a few people and a lot of “vocational” equipment. Vocational meant the stuff was for work – a job. It should be obvious that many of the things carried in the back of a pickup could smash through the back window even on a panic braking stop, or worse, during a crash. You can see the need for shielding the back window or using penetration-resistant back window glazing. Now look at big, heavy trucks that are not SUVs. These are the flat bed trucks or stake-side farm trucks. Such a truck is the truck tractors with a fifth wheel used to pull semi trailers. Many of these trucks hare equipped with a sturdy panel covering the entire back of the cab. It is essentially armor against a load shifting ahead. Based on that, don’t you think all pickup trucks should have a laminated glass back window?