We saw a very scary incident during the Cup race Sunday when Mark Martin was T-boned by the edge of the pit road wall. Luckily, the car hit the wall behind the driver’s seat — otherwise, that could have been very serious. (The link has the video).
The ends of walls are probably the biggest safety problem NASCAR has right now. The SAFER barriers have radically improved the ability of drivers to walk away from standard crashes, but there are still some vulnerable areas.
When a car comes to a stop by hitting a wall, it experiences some force. The SAFER barriers spread that force out over a longer time, so the peak force is less. The end of a wall poses a different types of problem. Pressure is the force the car experiences divided by the area over which the force is applied. When a car hits a wall broadside, the force is spread out over the entire area of the car’s side. The end of the wall presents a very small area. Given the same force, the narrow end of the wall creates a very large pressure – which is why we saw the wall intrude a good foot into the car.
The doors on both sides of the car are heavily reinforced with horizontal bars. The topmost bar sticks out further beyond the next bar down and so on, with the idea being that when the car hits the wall, the bars will successively give. Again, the idea is to spread out the force over time. There is also a sheet of Tegris (the material used in the splitter) in the door to protect against cockpit intrusions by something narrow enough to fit between the bars. The material also gives you an additional layer of reinforcement.
There are a lot of edges on the racetrack. The end of Pit Road is probably the most likely to create a hazard, but anywhere there is an opening in the wall, there is an edge.
If the edges of walls are known to be dangerous, why haven’t they been fixed? A couple reasons:
1. The chances of having a serious accident involving the end of a wall are small. NASCAR has to balance the cost of developing, testing and installing new safety devices with the likelihood that they will be called upon during a race. They’ve tried to anticipate the locations on the track where accidents happen the most and protect those first. Drivers hit inside walls far less frequently than they hit outside walls, so outside walls were the first to be addressed. Over the years, we’ve seen drivers hitting the inside walls at particular tracks and they’ve installed SAFER barriers there. Even Mark Martin said (in an article by Bob Pockrass) that this was a ‘freak accident’ and he wasn’t sure whether it was possible to protect against these rare occurrences.
2. This is a tough problem to solve. Think about the constraints: The safety device has to absorb a hit and not scatter material all over the track. It has to be able to be ready for a second hit almost immediately, so any solution that requires repair of the wall when there is a routine hit is going to be nixed. It can’t interfere with drivers getting where they need to go, or with emergency vehicles having access to the track. It has to be easy to retrofit and can’t cost too much.
A couple people suggested rounding the wall, so that it’s a semicircular profile instead of flat. Unfortunately, that decreases the area of contact. Making it a right angle so that there isn’t a wall end is a possibility, as long as you keep the corners rounded; however, a large round surface will either decrease the opening size or decrease the adjacent pit box.
One suggestion a lot of people had was to make movable gates that would cover the openings until they were needed. The big problem becomes: what if the car manages to hit the hinge (or other opening mechanism) and jams the gate so that you can’t open it? If we’re talking about one of the openings where you see emergency vehicles and people waiting so that they can respond quickly, you are delaying the time it takes for a potentially injured driver to receive aid. I know that research is ongoing as to how to adapt SAFER barriers to these openings. If they had a feasible solution, we’d be hearing about it already.
Another interesting solution NASCAR is considering was discussed in a Popular Science article from 2006: It’s a very special foam that can deform to 1/7th its volume during an impact, and then return to its original configuration within minutes. Called FlexAll, it was developed by Battelle and is currently being adapted for applications in the military and on the highways you and I drive — where the ends of safety barriers represent a major safety hazard as well. The problem with FlexAll is the cost: I’m seeing numbers on the order of $30,000 per wall end. That makes it suitable for the military, but difficult to justify for highways… or perhaps NASCAR.