IndyCar's official report into the fatal accident at Las Vegas Motor Speedway in October has been published, concluding that several factors occurring together in the worst possible combination resulted in the death of Dan Wheldon.

"There are multiple factors that are not uncommon to racing that came together in a way that claimed Dan's life," said Brian Barnhart, IndyCar's President of Operations. "It is a tragedy. Our thoughts and support will always be with Dan's family."

While the report did not find that high-banked ovals in themselves are unsuitable for IndyCar racing - "IndyCar and CART/Champ Car have successfully conducted numerous races over numerous years on courses that meet the definition of high-banked ovals," the report said - it was clear that the main factors had been an interplay between the existing Dallara chassis and the current Las Vegas Motor Speedway configuration that had been at the root of the accident.

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"Due in part to the geometry of the track, each track has its own unique routes around the circuit that optimize speed and handling capabilities," the report explained. "These routes are considered 'racing grooves' and create restrictions on where a driver can place the race car on the track to remain competitive. Most tracks have limited numbers of racing grooves. For example, it is not unusual for ovals to have only one or 2 racing grooves, including the Indianapolis Motor Speedway."

But in the case of Las Vegas Motor Motor Speedway, it emerged from analysis of the video playback that the variable-banked, multi-grooved and recently repaved surface offered an almost limitless freedom for drivers in the existing Dallara chassis to manoeuvre at full speed almost anywhere across the track during the race, and still be competitive. Combined with the expected close 'pack racing' seen on race day, this was what led to the instability that produced the first accident, the report by independent forensic crash investigators suggested.

"While this incident could have occurred at any track at any time, the dynamic of the current car and the overall track geometry at Las Vegas Motor Speedway under race conditions appears to have been causal to this incident," the report stated.

"What was evident in the Las Vegas event was that the entire racetrack was useable and the lanes were limitless," added Barnhart. "That was a variable that had not been seen before."

The report added that this hadn't been possible to detect in advance during the standard formal two-day compatibility and performance tests at LVMS on November 15, 2010 conducted by drivers Scott Dixon of Target Chip Ganassi Racing and Ryan Briscoe of Team Penske, or the private testing by IndyCar and Firestone Indy Lights teams that had followed. The multi-groove characteristic only emerged as teams fine-tuned their set-ups during the practice and qualifying sessions during the race weekend and started to race in packs at increasing speeds.

The immediate cause of the accident was contact between the #06 (James Hinchcliffe) and the #17 (Wade Cunningham) as they entered the first turn on lap 11. The right front of the #4 (JR Hildebrand) then made contact with the left rear of the ailing #17 which is what finally triggered the multi-car crash.

"The #4 climbed the left rear of the #17 and became airborne for a brief period of time," continued the report's account. "The #15 (Jay Howard) made contact with the #17 and then the #15 slid up the track and hit the outside wall with the right side of his race car. The #17 made contact with the #22 (Townsend Bell). The #22 spun and hit the wall with his left side. The #4 came back down almost on top of the #17 and both of them hit the outside wall almost as one with their right sides."

Approaching behind them at a maximum speed of 224mph, the #77 of Dan Wheldon stayed low on the race track to try and avoid the unfolding crash. But the #17 of Vitor Meira was spinning toward the infield and collecting the #59 (EJ Viso) and the #83 (Charlie Kimball) directly in front, which effectively blocked the path of the #77 that was two car lengths behind the collisions.

"Approximately 3.8 seconds before impact, the driver of the #77 reduced throttle to about 55%," the report explained. "Approximately one second later, the throttle was reduced even further, down to less than 10% and the throttle remained in this position until contact. The driver of the #77 applied the brakes for approximately 2.4 seconds prior to contact, and had decelerated to a speed of 165 mph as the right front of the #77 made contact with the left rear of the #83."

The #77 was launched airborne with G-forces of 24 longitudinal and negative 23 vertical. It rolled to the right in the air and travelled in a rearward direction in a nose up, semi-airborne state for approximately 325 feet until it made contact with the catchfence "in an inverted posture with the cockpit was open toward the fencing.

"The chassis of the #77 impacted a post along the right side of the tub, created a deep defect in the tub that extended from the pedal bulkhead along the upper border of the tub through the cockpit," the report detailed. "This resulted in angular deformation of the roll hoop that was sheared off the tub from right to left. As the race car passed by, the pole intruded into the cockpit and made contact with the driver's helmeted head.

"This impact produced non-survivable blunt force trauma injuries to Dan's head," stated the report. Despite the fact that the right front pull rod of the #77's suspension had been driven into the driver safety cell, "The suspension did not make contact with the driver, or penetrate his uniform ... Dan's injury was limited to his head injury."

The report went on to describe the next series of collisions between the #57 (Tomas Scheckter), the #8 (Paul Tracy), the #30 (Pippa Mann), and the #19 (Alex Lloyd) that had resulted in Mann being launched into the air for some 240 feet and landing upside down; and then detailed how the nose of the #12 of Will Power impacted Lloyd's left rear tyre and was launched into the air for 315 feet before landing right side up. Mann received burn injuries to her hand which are still receiving treatment, while Power suffered some compression injuries to his back from the impact that have required him to wear a brace during his recovery.

The account finished by stating: "The above analysis of the sequence of dynamic events revealed no extraordinary car-interactions or interactions that were specific to this incident that have not been encountered in other races. The impact with the fence that resulted in Dan's non-survivable injuries involved circumstances of location, direction, and orientation that were the chance result of the previous interactions."

The SAFER barrier and other safety measures that came into play "appear to have functioned as designed during the accident," and were repaired within the hour so that racing could have been resumed if directed by race control, although 13 cars had been written off in the accident.

As a result of the report's findings linking the design of the car with the track configuration as main causes, the report comments that with the introduction of the new DW12 chassis from the start of next season, "Further testing is appropriate to evaluate the dynamic between the new race car and the specific geometry of this track." IndyCar announced last week that next year's scheduled race at Vegas had been cancelled to facilitate exactly this sort of testing.

However, the report disagreed that 1.5-mile ovals as a class should now be dropped. "IndyCar has determined that it would not be appropriate to frame its analysis of the suitability of IndyCar Series race cars to high-banked ovals by looking at all tracks of this classification as a general category," the report said. "Each high-banked oval has unique characteristics, and each should be considered individually."

The report's findings could therefore clear the way for IndyCar to sign a deal to return to another high-banked 1.5 mile oval in 2012, Texas Motor Speedway, without fearing a recurrence of the tragic events of Vegas.

The report went on to discuss other factors that had been suggested as causes. The suggestion that there had been too many cars on the track had not significantly contributed to events, the report found. It calculated that on a 1.5-mile oval, 34 race cars permitted 233 feet per race car which was within acceptable parameters based upon a number of factors such as length and width of the race track, travel considerations, pit space capability and the manoeuvrability of the cars.

The report also pointed out that NASCAR Sprint Cup raced with 43 cars earlier in the year and NASCAR Camping World Truck Series had raced the day before the accident with 34 vehicles on track, with no problems emerging, and therefore concluded that the accident seen on October 16 could have happened with any size starting field.

"However, the previously discussed experience with freedom of movement during the race does create questions of whether an IndyCar starting field of any size is appropriate in the future," the report added. "This will be a topic for further review and investigation based upon the 2012 car dynamics."

The report also assessed and included resum?s of all the drivers racing that day and pointed out that "All drivers had prior experience in the IndyCar Series and/or other racing series. Of particular note, no driver was participating in his/her first IndyCar Series race event at Las Vegas Motor Speedway. In addition, 5 drivers had previously won the Indianapolis 500 Mile Race at least one time."

The report specifically praised the efforts of the Holmatro Safety Team and the Las Vegas fire crew, which were described as "rapid and decisive" in the aftermath of the accident.

"All drivers were out of their race cars in a rapid and controlled manner, and assisted as needed. All of the fires were extinguished rapidly and without incident," said the report. When it came to efforts to save Wheldon himself: "Extrication of the driver of the #77 was temporarily impeded by entrapment of the lower extremities. This situation was dealt with without interruption of life support measures. The Safety Team was on the scene with the #77 within 35 seconds of the initial impact in the multi race car crash, and the driver was extricated from the race car within 4 minutes."

Wheldon was stabilised in the infield care centre and flown to hospital by helicopter, but was declared dead on arrival from the head injuries that he had sustained.

The idea that the $5m challenge had in some way contributed to the accident was also dismissed. While the rules of the challenge had put Wheldon at the back of the grid, the report pointed out that penalties, post-qualification changes and other incidents often see a driver start from the rear without adverse affects.

"No conduct by Dan Wheldon's driving of car #77 during the course of the race including lap 11 was found to have contributed to the cause of the racing incident or its consequences," the report found. "Furthermore, no conduct by any drivers on lap 11 was found to be inconsistent with expected driving during the race."

As a result of the details of the impact, the report commented that with regard to the make and manufacturer of racing helmets for drivers, "There is no current evidence that one type is preferred and should currently be mandated over another. Even given the known nature of the head injury to Dan, the choice of helmet was specifically found not to change the consequences as to this injury."

The report did not directly address the 'open-wheel' nature of the IndyCars and whether this had been a critical factor. The new DW12 chassis includes new features that have been been criticised by some fans and drivers as "bumpers" to protect the cars from wheel-to-wheel direct contact in 2012 that might have prevented some or all of the multiple-car wreck seen at Vegas.

"IndyCar's commitment to safety was enhanced by Dan Wheldon's testing throughout 2011 of the new car to be used by IndyCar in 2012," said the CEO of IndyCar, Randy Bernard. "We are thankful for his efforts and commitment to racing."

The report concluded:

The accident was significant due to the number of race cars damaged, but more importantly due to the non-survivable injuries to Dan Wheldon. While several factors coincided to produce a 'perfect storm,' none of them can be singled out as the sole cause of the accident. For this reason, 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.

IndyCar is committed to safety. This report is an interim step to IndyCar's on-going efforts to improve motorsports safety. IndyCar will continue its efforts to reduce the risks of racing to all.

The 2012 racing season ushers in an era of a new IndyCar Series race car and the opportunity for unprecedented safety advancements. Dan Wheldon was instrumental in the testing and development of this new car and the safety innovations that it represents.

The thoughts, prayers and deepest condolences of IndyCar and the open wheel racing community go out to Dan's family.

The full report can currently be downloaded from related links on the article on the Indianapolis Star website.