This weekend marked the death of Dan Wheldon, the 33-year-old English race-car driver who went careening to his death after a 15-car pile up at the 2011 IZOD IndyCar World Championship at the Las Vegas Motor Speedway on Saturday. Wheldon had won the Indianapolis 500 in 2005 and 2011.

Wheldon's tragic death has raised questions about the safety and regulations of the motor sport races. The seven-time champion's death is the subject of intense scrutiny, and IndyCar officials are facing many questions. One major issue is the oval-shaped arenas with high banking and the effects this shape has on the speed levels of the drivers. Another major issue is pack racing, which leads to multi-car pile ups and collisions. Major racers have suggested changes to the shape of the cars and more protection on the wheels. 

Despite the need for changes and regulations, the unfortunate fact is that the dangerous sport often leads to the death of even the best drivers. We take a look at five top drivers, besides Dan Wheldon, who were killed in the Indianapolis 500 over the years.

5. Dave MacDonald (1964) 

In 1964, Dave MacDonald's brilliant career ended abruptly when he was one of two drivers that was killed in a fiery inferno in the 164 Indianapolis 500. He died at the age of 27.

Dubbed the Master of Oversteer, MacDonald had competed in 101 races, having 44 victories and 65 top three finishes. He was most well-known for driving Chevrolet Corvettes.

I think Dave had more raw talent probably than any race driver I ever saw, Carroll Shelby told Hot Rod Magazine in a 2008 interview. 

4. Eddie Sachs (1964)

Eddie Sachs, known as the Clown Prince of Auto Racing, died on May 30, 1964.

His career included 8 USAC Championship Trail wins and 25 top-five finishes in 65 career AAA and USAC starts. He started at the Indianapolis 500 eight times winning the pole position in 1960 and 1961.

He famously said that, I'd sooner finish second than be dead. Unfortunately for Sachs, he was killed alongside Dave MacDonald in the fiery crash that involved seven cars in the second lap of the 1964 Indy 500.

The 1964 Indy 500 crash was the first time in history that the race was stopped because of an accident. Since then, every race has used methanol or ethanol based fuels instead of gasoline-powered cars.

Sachs coined the phrase, If you can't win, be spectacular.

3. Pat O'Connor (1958)

Pat O'Connor was killed in a 15-car pileup after sustaining a major head injury after his car caught fire during the first lap of the 1958 Indianapolis 500.

When Ed Elisian spun out of control and hit Dick Rathmann during the 1958 race, they started the beginnings of a 15-car pile-up. O'Connor's car hit Jimmy Reece's. O'Connor's car then flew fifty feet in the air, landed upside down, and burst into flames. He was incinerated in the flames, but probably died first from a fractured skull.

O'Connor had participated in five World Championship races, but won no World Championship points. He finished 8th twice. 

2. Bill Vukovich (1955)

Bill Vukovich, a Serbian American race car driver, was violently killed in the 1955 Indianapolis 500.

The 36-year-old driver was killed in a chain-reaction crash on the 57th lap of the 1995 Indy 500. When two drivers lost control of their cars, Vukovich hit Johnny Boyd's car, which was in his path. Vukovich's car flew through the air, landed upside down, after numerous somersaults, and burst into flames.

Vukovich was the second defending champion to have died during the race (Floyd Roberts, being the first in 1939) and he was the only former winner to have died while being in the lead.He had numerous nicknames, such as Vuky, The Mad Russian, The Silent Serb, Fresno Flash and Vuke. He is known as one of the greatest drivers in the sport.  He won the 1953 and 1954 Indianapolis 500 and two other AAA National Championship races.

1. Floyd Roberts (1939)

Floyd Roberts was killed in the 1939 Indianapolis 500 after winning the race the year before with the same car with a record speed of 117.2 mph.

During the 109th lap of the race, Bob Swanson lost control of his car and Roberts' car hit him. Swanson's car flipped over, caught fire, and Swanson flew out. Roberts' car, on the other hand, went straight through the outer wall of the arena and into a tree. Deby flew everywhere and another driver was also flipped. Roberts' death was due to brain injuries and he was pronounced dead before the race's end.

Roberts was the first former winner and defending champ of the race to be killed during the competition. It seems that Roberts intended to retire following the 1939 race.