NASCAR, Formula One and IndyCar are all lumped together under the heading of auto racing, but the world's three most well-known series have some major differences in speed, style of racing, types of cars and tracks. Here's a rundown:
IndyCar: It's an open-wheel circuit like Formula One, but the ethanol-burning cars are bigger and tend to race at higher speeds despite having less horsepower. IndyCars race on similar tracks as NASCAR, but with more of an even split between ovals and street courses. Top speeds can reach close to 225 mph at big tracks with long straightaways such as Indianapolis Motor Speedway or Las Vegas Motor Speedway, where Dan Wheldon was killed Sunday during a 15-car pileup. The series will switch to a new chassis and allow for a variety of engine platforms in 2012.
Formula One: The cars are much more technical and expensive than IndyCar, along with being smaller and more agile. Races start from a dead stop, unlike IndyCar and NASCAR, and are run on race and street courses -- never ovals -- throughout Europe, Asia and the Middle East. The cars have between 750-800 horsepower, but speeds rarely reach 210 mph because of the twisting and turning of the courses on the circuit. Races usually involve a lot of passing, and drivers tend to keep from getting bunched up, like in the other two circuits.
NASCAR: The top-level Sprint Cup series has stock cars designed to look like those driven by everyday people, though far more powerful. A purely American sport, NASCAR's roots come from bootleggers running alcohol in souped-up cars. Because the cars are heavier and covered in rolled sheet metal, drivers can bang into each other -- "trading paint" in the parlance of the sport -- without causing too much damage. Cars rarely approach 210 mph, and big tracks such as Daytona and Talladega require restrictor plates, which keep speeds down.