On track at the Indy 500.

After years of potentially deadly smash-ups, a redesigned track keeps drivers in the race.

At the Indianapolis 500, tradition reigns supreme. The race is always on Memorial Day weekend. It's always preceded by a stirring rendition of "Back Home Again in Indiana." And before the checkered flag comes down, at least one driver has a horrifying brush with death.

Like the time Rick Mear's car smashed into the wall, spun 3-1/2 times, flipped over, and slid upside down for 220 meters (see photo, below). That was during a practice run for the 1992 race.

Amazingly, Mears escaped with nothing worse than a fractured foot and a sprained wrist. Other 1992 drivers weren't as lucky. Jovy Marcelo died from a blow to the head when his car skidded into the wall. Nelson Piquet's left foot was almost severed, pulverized beyond recognition, according to one doctor, when his car struck the wall head on. Jeff Andretti suffered a concussion and severe fractures of his feet and ankles in a similar crash.

But this year something was different. Aside from a few minor burns, "the only injury we had was a bruised knee," says Kevin Forbes, the Indy's director of engineering and construction. The reason? Changes in the track, Forbes says.

'ROUND THE BEND

After the brutal 1992 Indy--with 27 accidents in all--Forbes and his team investigated how they could make the track safer. They decided to add a grassy area inside each corner. Their aim was not to provide a "cushion," but to keep racers from driving in a warmup lane that used to run alongside the track (see diagram, p. 14).

The change makes the track more challenging, because drivers who used to cut across the warm-up lane now have to make tighter, sharper turns. That may sound more dangerous. But if you study the physics, you'll see how it makes drivers--usually concerned with nothing but speed--take the turns at a slower pace.

If you've ever taken a turn on a bike, you already know that the faster you go and/or the sharper the turn, the greater the chance that you'll crash. Same goes for Indy cars.

The problem is that the laws of physics have more control over moving objects like bicycles and Indy cars than their drivers do.

One of those laws, Newton's first law of motion (also known as the law of inertia), says that when an object is moving in one direction, it will tend to keep moving in that direction. To make the object change direction--to turn--you have to overcome its inertia by applying a force, a push or pull.

At the Indy, "you spend 60 percent of your time turning," says driver Lyn St. James. There are 800 left-hand turns in the race. That means constantly fighting inertia to keep the car from flying into the wall.

Where do drivers get the force for all that turning? It comes from the friction between their tires and the road. Track designers help out by banking the turns--angling the roadway inward so that a car's weight helps pull it through the turn, just as leaning into a turn helps you on your bike. Together, the friction and the tilt make up what scientists call a centripetal force--a force that pushes an object toward the center of a curve.

DANGEROUS CURVES

The thing is, the faster you try to take a turn and/or the sharper you try to make it--the more rapid or great the change in direction--the more centripetal force you need. But the amount of centripetal force a driver can call on is out of his or her hands, says racing engineer Forbes. Of all the fancy controls in an Indy car, not one button says "Increase Centripetal Force."

And no amount of skill can help. Without enough inward push, not even Isaac Newton himself could make it through a turn. He and his Indy car would fly off the road (in a straight line from the point where traction was lost) and go SMACK! into the wall . . . as ambulances raced to the scene.

To avoid such smash-ups, racers on the new Indy track must adjust their driving, says Forbes. Since the new tighter turns require more centripetal force, drivers have to compensate, he says. They reduce the need for force by slowing down. That ensures that the friction they have will be enough to overcome the car's inertia and carry them safely through the turns.

The changes seem to have been a success. Though slightly slower than the accident-ridden 1992 race, this year's was no snoozer. In fact, many people felt it was more competitive. "We had ten cars on the final lap, all on the same lap at the end of the race," says Indy spokesperson Bob Walters, who adds that it's normal to have only three. And more than half of the 33 cars that had started were still racing.

Maybe the new track made the drivers more aware of an old racing proverb: "To finish first, first you must finish."