Race driver Dan Wheldon was killed when his head hit a fence post at the Las Vegas Motor Speedway - contact that created a "non-survivable injury" to the double Indianapolis 500 winner.The cause of death was revealed at the weekend when IndyCar presented the findings of an investigation into the October 2011 multiple crash at the track that involved 15 cars, including Wheldon's, after he came from behind the initial contact, launched over spinning cars, and flew about 325 feet into the catch fence that protects the audience from flying debris.SEVERAL FACTORS - 'PERFECT STORM'Although contact with the post killed Wheldon, the investigation determined that several factors contributed to what became "a "perfect storm"."The accident was significant due to the number of race cars damaged but more importantly due to the non-survivable injuries to Dan Wheldon," the report said. "While several factors coincided to produce a 'perfect storm' none can be singled out as the sole cause."So, it is impossible to determine with certainty that the result would have been any different if one or more of the factors did not exist."The race had a season-high 34 starters but IndyCar CEO Randy Bernard said the field could have had 37 based on the size of both the track and the pits lane. The season finale was held on Vegas' high-banked, 2.4km oval with multiple racing lines, which IndyCar president Brian Barnhart said created "nearly unlimited movement on the track under race conditions".That, not the construction of the fencing, played a larger role in Wheldon's death.VARIABLE BANKINGBarnhart admitted IndyCar was not prepared for the drivers to have free rein a wide-open race track. Most ovals have only one or two racing lines which, the report said, restricted drivers' naturally aggressive racing behaviour (and) made the location of other competitors' cars on the race track predictable.As this was IndyCar's first visit to Las Vegas circuit since 2000 few of the drivers had experienced on the variable banking or wide surface - but drivers did predict racing at Las Vegas could be hairy as early as pre-season testing. Marco Andretti was one of the first drivers to publicly question the track, which would "be easily wide open, which is going to create a big pack"."It's going to be fun for the fans. I like those races, but it'll be dangerous," he added.That view was repeated in the build-up to Las Vegas by many top-name drivers and all weekend as speeds got closer to 350km/h during practice yet IndyCar was surprised when the race began. Barnhart said: "I don't think we were expecting it to be any different from what we'd experienced in the last decade at (other tracks), places where while there is the ability to run flat and there's multiple grooves, you couldn't run from the top of the race track to the bottom."We were never expecting to be able to run from the top to the bottom (at Las Vegas)."GUIDELINES VITALBarnhart stressed IndyCar never had a chance to duplicate race conditions, so no amount of testing or practice would have prepared anyone for what happened when the race began.Barnhart said it was imperative for IndyCar to establish guidelines for the drivers on tracks such as Las Vegas and the series needed to look at aerodynamic changes "to make the cars more challenging to drive"."We need to create a limit," he said. "Drivers have to understand there is a line they can't cross."IndyCar also addressed the $5-million prize promotion that featured Wheldon. He was making only his third start of the season and chasing the incentive offered by Bernard to any non-IndyCar regular who could drive from the back of the field to win the race.Wheldon would have split the money with a fan selected in a random drawing.IN-CAR COMMENTATORAllowing Wheldon to take the challenge was a stretch - he'd won 14 races on ovals, including the Indy 500 - but because he sat out the season he technically qualified for the bonus - but Wheldon felt he was up for the challenge. He was the in-race reporter for ABC during the event and spoke with the announcers during the warm-up laps. In a brief interview, Wheldon defended his participation and the entire IndyCar Series."I wouldn't be doing this if I didn't think that I can win," he said from his car. "Certainly I am not underestimating the talent of the other drivers in the field. I think IndyCar has got a phenomenal field right now."Wheldon was killed minutes later when the crash began ahead of him at the start of lap 12th. He had picked his way through the field and gained at least 10 places when he came upon the accident and had nowhere to go to avoid the spinning cars and flying debris.The report found that although Wheldon stayed low on the race track and appeared to be attempting to avoid the cluster of cars spinning toward the top - he had slowed from 350km/h to around 260km/h - his path was blocked by other cars. His first contact with another car launched him into the air.NO RACE IF IT ISN'T SAFEQuestions remain about Las Vegas' future on the IndyCar schedule. Bernard had a three-year lease agreement with the track to stage the season finale at Las Vegas through to 2013 but came to an agreement with SMI last week to buy out next year's portion of the contract."I think Las Vegas is a great city, a resort destination, and our fans and sponsors - everyone loves the city," Bernard said. "But I don't want to go back there if the conditions aren't right, it isn't safe, for our race cars."IndyCar plans on judging all high-banked ovals individually in future but said the Wheldon accident could not be blamed on the banking. That left room for a deal to be worked out with the Texas Motor Speedway, one of the most popular venues on the IndyCar calendar.No sanctioning agreement between Texas and IndyCar has been agreed.