Brandon Jones hit the end of the pit road wall during Saturday’s XFINITY race, prompting a lot of people to ask if sand barrels are the best we can do in terms of safety.
Pit Walls Have Always Been Dangerous
Thankfully, the worst part of Jones’ crash was that he turned the pit entrance into a beach, and it took forever to clean up. In 2012, Mark Martin t-boned the pit road wall at Michigan. Martin’s car hit behind the driver’s seat, or it would have been much more serious. In 1990, Michael Waltrip survived a similar type of crash at Bristol that left nothing but the roll cage intact.
The ends of walls are motorsports’ biggest safety problem. Their danger was highlighted when driver coach Gary Terry died in May of 2015 while teaching on a track that was being run in the wrong direction. While SAFER barriers and safer car have allowed drivers to walk away from scary crashes, the ends of walls remain a danger.
Why Can’t We Put SAFER Barriers on Pit Walls
We could; however, the problem is the end of pit wall (or really, any wall). SAFER barriers spread out the force of impact over a longer time and a bigger area As you can see in the video below from the University of Nebraska, the car moves the barrier several feet ahead and behind the actual impact. Spreading out the impact subjects the driver to less force.
Wall end pose a different problem because the force is concentrated in a very small area. It’s the difference between stabbing yourself with the pointy end of a just-sharpened pencil or the eraser end.
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.
Since SAFER barriers aren’t an option for pit wall ends, most motorsport tracks employ:
- Light plastic barrels full of sand
- Light plastic barrels full of water
Some people were concerned that the barrels broke so easily when Jones impacted them. They’re designed that way. The barrels’ only purpose is containing the sand until it’s needed. Heavier barrels would create more force on the car. Energy is required to move or break anything. When the barrels break, energy from the car dissipates through the barrels — instead of through the driver. Most, or all, of the car’s energy is thus gone if the car reaches the end of the pit wall.
Sand (or water) are good ways of packing easily dispersible mass into relatively small volumes. Each individual grain of sand (or drop of water) isn’t very heavy, but there are a LOT of them there. Each bit of sand that goes flying takes energy with it.
Tire stacks work a little differently. They use energy to deform the tires. The problem is that the tires store that energy like a spring. And, like a spring, they return some of it. Tire barriers can shoot a driver back out into traffic. For NASCAR tracks, tires aren’t a very good choice.
Why Hasn’t Someone Invented a Solution?
People are working on solutions, because this problem doesn’t just exist on the racetrack. The ends of highway guardrails can cause serious injury if they’re not protected. But the solutions that work for a car going 70 mph often won’t work for a car going 180 mph.
So why aren’t we seeing these solutions?
- Rarity of Occurrence: I can only recall a few accidents of this type in the last thirty years. Even Mark Martin said that this was a ‘freak accident’ and he wasn’t sure whether it was possible to protect against these rare occurrences.
- It’s a hard problem. Think about the constraints: The ideal safety device would:
- Take a hit and still be working so that a second hit in the same place is protected.
- Not scatter material all over the track.
- Be quickly repaired or replace
- Can’t interfere with drivers or emergency vehicles
- Must be easy to retrofit
- Can’t cost too much.
Battelle Labs filed a patent in 2006 that was highlighted by Popular Science. Battelle created a special ‘hyperelastic’ foam that can deform to 1/7th its volume during an impact, and then return to its original configuration within minutes. The drawing below, from the patent, shows the foam (which they then called FlexAll) as long, squarish vertical cylinders.
The diagram above also shows some collapsible metal bars, which I believe were being considered for highway applications, but not necessarily racing. The problem seemed to be the cost: At the time, numbers were on the order of $30,000 per wall end. Battelle has developed this barrier for highway applications (as of 2019) and has adapted the foam to use for lightweight armoring. They’re also looking into using it for impact and vibration dampening applications.
NOTE: This blog includes some material from a post that was originally published on 2012-08-19.