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Indy 500: Energy Dissipating Wall Installed at Speedway

20 May 1998

INDIANAPOLIS - Safety for drivers in this Sunday's Indianapolis 500 was enhanced even further this week as a newly designed energy-absorbent and resilient barrier was installed on the inside of Turn 4 of the Indianapolis Motor Speedway.

This will be the first time in the history of the track, opened in 1909, that something to soften crashes has been attached to the walls of the storied Brickyard.

"I feel it is incumbent on us to be the leader in the forefront of safety development," Speedway President Tony George said. "I lend my complete support to this project."

On May 18, workmen began installing the new wall facing, made of black high density polyethylene material. The 5-foot-long, overlapping impact plates will stretch 550 feet north on the wall, starting on the inside of the racing surface just beyond the pit entrance. The official name for the wall barrier is Polyethylene Energy Dissipating System or PEDS Barrier for short.

Each module contains two 16-inch-diameter cylinders of the same polyethylene material that are bolted to the impact plates. The upper portion of the impact plate is folded over the top of the cylinders. Every module is anchored to the concrete wall with steel cables that will secure it firmly if the wall is struck by a spinning car.

When a race car strikes the impact plate, the cylinders compress, reducing the impact against the unmovable wall behind it. The flexible polyethylene material then returns nearly to the original configuration.

"It compresses and then slowly returns to the original shape," said designer John Pierce, retired engineer from GM Motorsports who serves as a safety consultant to the Pep Boys Indy Racing League.

The barrier system is being installed only on the inside of the Turn 4 wall for initial testing. The inside wall is considered a low risk area, Pierce said.

Dr. Henry Bock, Speedway director of medical services, said the Speedway began serious talks about building protective barriers when the new walls were reconstructed around the track before the first Brickyard 400 in 1994.

There have been many proposals for padding the walls, but none seemed optimal for open-wheel, high-speed racing.

"Safety really came to light in the last two or three years, when we had those injuries (from crashes into the walls)," Bock said.

Bock noted that making the car more crash-worthy was the first step. The next was to explore other means of protecting the drivers.

"This last year we went strongly toward safety and aggressively went after this," he said.

Leo Mehl, executive director of the Pep Boys IRL, said everyone realized that league races take place on oval tracks where "brave and fearless race drivers" are going to run into concrete walls.

"And we must be prepared for that," Mehl said. "The current design in our testing has reduced the impact up to as much as 50 G's of energy. We were reluctant to put it on an outside wall, because we needed experience in construction. We know one thing: You are much better off hitting this barrier than you are hitting concrete."

The IRL Safety Committee investigated the feasibility of using polyethylene cylinders as impact energy dissipaters, Bock said. These cylinders, a commercially available petroleum product, are frequently used as barriers on public highways.

The Safety Committee, which includes Kevin Forbes, director of engineering facilities at the Speedway, assigned Pierce to design a feasible, workable wall "shock absorber." Pierce evaluated about 10 designs during the past year before selecting the one now attached to the wall. The system was refined after extensive impact-sled testing at Wayne State University in Detroit.

The impact-plate modules were built in the Speedway construction area located in the northwest corner of the Speedway. Two 5-foot-long sections were tested by driving a front-end loader into them several times. Much innovation was required from the construction crew, headed by Wayne Leminger.

"Nobody had previously worked with this material, so everyone pitched in with ideas," Leminger said. "All the work has been done during the past 10 days."

An especially challenging problem was bending the polyethylene impact plates. This was solved by heating a section of the impact plate, quickly folding it to the proper configuration and holding it during cooling.

The first hint that something was being added to the inside of Turn 4 was when the workmen began drilling 300 holes along the bottom of the wall for the retention cables. The 160 modules were fabricated in an assembly line fashion after the construction problems were resolved.

The PEDS Barrier wall was in place for the two-hour Carburetion Day practice session Thursday and for Sunday's 500-mile race.

"Once we get some experience with this PEDS Barrier, we ultimately would like to put it around all four corners here at the Speedway," Mehl said.

"The beauty of it is the possibility for applications on the outer walls, and that's what we are really looking for, not only at this track but others," George said.