Approaching the last corner on the final lap of the inaugural Formula E race in Beijing, Venturi’s Nick Heidfeld was edging ever closer to the rear wing of Nicolas Prost’s e.dams-Renault. Both vying to become the winner of the first fully-electric single-seater race.

Heidfeld pulled out of the slipstream to make a move for the lead but Prost steered across track to defend his position. As they touched wheels Heidfeld’s front-right suspension broke, sending his car out of control.

Unable to slow down, Heidfeld hit a kerb and launched into the air before violently smashing into the barrier on the outside of the final corner, eventually coming to a halt upside down. Prost would subsequently be handed a 10-place grid penalty at the following race in Putrajaya for causing an avoidable collision.

As Lucas di Grassi snatched an unlikely victory, Heidfeld crawled unharmed from the wreckage and sprinted across the track to confront Prost, although the two drivers – who are team-mates at Rebellion in the WEC - have since made their peace. So how can a driver walk away from such an accident and what procedures are in place to ensure safety is a top priority for everyone involved?

FIA crash test

As with the cars you drive on the road every day, the Spark-Renault SRT_01E had to undergo rigorous mandatory crash tests to simulate various accident scenarios. Introduced in 1985 and supervised by the FIA, all crash tests are designed to minimise risk, check loadings and evaluate vehicles prior to them being certified safe to race.

As is the case with most other single-seater series, the Formula E car is built around an aluminium and carbon-fibre monocoque. This acts as a survival cell for the driver and also the principal component for the chassis design, which incorporates the powertrain and front suspension mounting.

In the event of an accident the surrounding parts of the car are specifically designed to break away and absorb energy on impact leaving the tub intact.

Carbon-fibre has been used in motorsport for over 30 years and has been critical in the development of both safety and on-track performance. Expertly woven, the carbon-fibre layers create a honeycomb effect that is not only incredibly strong but also lightweight. The process to make each part, whether it’s the front wing or crash structures, is long and painstaking.

The Formula E chassis is produced by Dallara whose staff have to carefully craft a pattern mould to precise dimensions before cutting the carbon-fibre into shape. Each layer is then formed around the cast to match the original design. This process can be repeated to produce over 50 layers if necessary. Once ready, the component is then transferred into an autoclave and exposed to high temperatures and various atmospheric pressure levels to cure the resin embedded in the carbon-fibre cloth.

After the precise manufacturing stage the Formula E car is subjected to a number of impact tests, which include roll structure and static load tests.

How do the tests work?

The format for crash testing is very simple. The impact tests are dynamic tests where the chassis is driven at solid objects. The monocoque is bolted to a sled and equipped with a crash-test dummy. To measure impact force the sled is pulled by cables into the object at a predetermined speed.

Following impact the damage is assessed to examine whether the car can stand up to high loads at the front-end where the driver’s feet are most exposed. The actual speed of the sled on impact is relatively slow but it is representative of a much faster accident. Despite the Formula E car being capable of in excess of 150mph, the test is only conducted at 38mph. However, because the impact is with a solid immovable object as opposed to the deformable barriers around the race track, it is representative of the forces encountered in accidents that are experienced at racing tracks.

Additional calculations are taken from static load tests where the Formula E car is subjected to numerous loads at selected points around the roll structure and chassis. These check the strength and integrity of the tub and allow for minimal levels of damage. One such test is on the roll hoop above the driver’s head, which in the case of Nick Heidfeld, played a key part in protecting his head when the car landed upside down. A nine-tonne vertical force is applied to the roll hoop, with the car failing the test if the construction is deformed by any more than 25mm.

Subsequent tests apply loads to the rear crash structure, cockpit sidepods and floor. As the Formula E car is the first fully electric single-seater extra care had to be taken to ensure the safety requirements were tailor made for the powertrain and battery-housing.

The battery

Williams Advanced Engineering, part of the Williams group of companies that includes the world famous Williams F1 Team, supply the Formula E lithium-ion batteries.

Speaking after Beijing, Williams explains the safety measures in place surrounding the battery.

“We have designed the battery according to the FIA's rules and regulations, car specifications from SRT, UN airfreight transport specifications, and our own expertise in designing high performance batteries. Working together with Dallara, SRT and RSF1, we have designed the battery safety cell based on patented Williams battery case technology. After manufacturing, Dallara fulfilled the stress test levels defined by the FIA.

“Whilst working on the battery case, we were running CAE analysis on the internal fitting and fixing for the impact levels expected by FIA crash tests and the UN38.3 test regime. It has been the first battery to pass FIA crash tests as a fully live battery, and did so at the first attempt. Then it achieved UN38.3 test specification vibration and shock profiles.”

Williams has enormous experience of developing batteries through the work it did on KERS in F1 and with the Jaguar CX75 supercar prototype. To ensure maximum safety, it monitors each cell voltage and temperature and ensures the battery stays within safe operating limits.

Although the battery in Heidfeld’s car was still functional after the crash, because there was some damage to the casing, it will not be raced again.

Williams said: “Once we receive the battery back at Grove, we will do further inspections. As the battery case is mechanically damaged we will not be using the battery as it is. Based on this further analysis we may decide to use some of the parts of the battery in future.”

The quest to make motorsport as safe as possible is one without end, and Formula E and the FIA will always be evaluating the crash testing procedure. However, it is a credit to the work that was done by the governing body, the series and its partners, that despite the ferocity of the impact, Heidfeld suffered nothing worse than a bruised shin.