The problem sausage kerbs continue to cause

If the 2022 Austrian Grand Prix taught us anything, it's that it is difficult to police track limits. Both the Formula 1 and supporting races were littered with multiple warnings for cars being driven outside of the defined track, to the point where the overall results were in danger of being significantly changed.

Of course, any driver will exploit an available advantage and push the limits of what is acceptable. But, equally, they will not deliberately put potential points at risk. The obvious conclusion is that something wasn't working as intended.

If we accept that lining the circuit with hard barriers is a non-preferred option, then there needs to be a practical system for ensuring a driver stays on the designated circuit while allowing for mistakes or incidents where breaking track limits is unavoidable.

As an FIA spokesperson points out, there's also a safety issue to consider here. All barriers and run-off areas are specified to be suitable for the speed of the car at that location when it is on the circuit. If a car is travelling at race speed nearer to a barrier than intended, then the effectiveness of these measures in the event of an accident will be reduced.

There are a number of ways this problem can be approached beyond active observation and reporting. But one of the most common solutions that's been in use for over 25 years has recently become the subject of renewed criticism after a spate of dramatic incidents.

The Combination Kerb, or ‘sausage kerb’, is a rigid rounded blister, a maximum of 12cm high, that is placed behind a lower 80cm wide kerb that borders the track. Its primary purpose when introduced was specifically to tackle the problem of drivers exceeding track limits and gaining an advantage. Running over one, especially in a hard-sprung single-seater is at best going to be uncomfortable and will risk causing damage to your vehicle.

Track limits penalties were handed out in their droves at the Red Bull Ring

Photo by: Bryn Lennon - Formula 1

Ex-F1 driver and TV pundit Karun Chandhok, when asked, revealed that he disliked them from the start. Today, he thinks they can work in the right location and specifically cites the exit of the Red Bull Ring's Turn 1 as an example of this. But he also leaves no doubt that he would like to see them removed.

What is clear is that the problems with the kerbs go far beyond having to deal with the consequences of their intended effects. If the higher kerb is run up against, or hit with a glanced blow, then it works as a deterrent. But if hit head on, or slid into sideways, then the result can be much more dramatic.

Searching YouTube reveals any number of clips featuring cars crashing catastrophically after hitting these kerbs, but all of them fall into two groups that can be categorised as ‘loss of control’ and ‘launching’. To understand what goes wrong, we need to consider how the energy of a moving vehicle affects its behaviour.

A very rapid change of a large nature due to a fast car or high kerb, will impart a large amount of energy into the car structure and driver - effectively creating a violent, direct impact

Every object in motion has momentum, a force that tries to keep it moving in a straight line at a constant speed. This is the reason that a car allowed to freewheel will coast until air resistance, gradient and friction gradually slows it down. It is also why a car travels in a straight line unless a new force, for example through the steered wheels being turned, makes it change direction.

Critically, momentum increases if the object is made heavier or the speed is increased. When hitting a kerb, the momentum will try to make the car continue in a straight line. But if it cannot, then the car will be deflected instead. This will reduce the speed a little, but the remaining momentum will then try to make it continue travelling in the new direction.

In all cases, the size and rate of change has to be considered. With a low kerb, or slow car, there will only be a slight deflection from the original path in a relatively gentle manner. The opposite of this, a very rapid change of a large nature due to a fast car or high kerb, will impart a large amount of energy into the car structure and driver - effectively creating a violent, direct impact. A fast car hitting a large kerb will have a high momentum, coupled to a large impact and large change in direction.

In most cases, striking the Combination Kerb only creates a momentary problem. But there are a worrying number of cases where it has initiated an accident in a manner unique to this design. One such incident was the Formula Regional European collision between Prema team-mates Dino Beganovic and David Vidales at Monza in 2021. Both cars left the track and cut across the second chicane, but as they were rejoining Vidales ran squarely onto the end of a ‘sausage kerb’.

 

His car underfloor was pushed up with sufficient force to throw the front wheels clear of the track surface for a significant amount of time, before momentarily touching down again just before landing and bouncing into Beganovic. Although Vidales's car did not become airborne in its entirety, it was completely out of control, with the Spaniard unable to steer. The impact when the nose finally returned to Earth cannot have been insignificant either. This is an example of ‘loss of control’.

The more spectacular problem occurs when the speed or angle of impact with the kerb means that the car is launched and becomes completely airborne. Two recent examples evidence this - the crash involving Formula 2 racers Roy Nissany and Dennis Hauger at Silverstone and Henrique Chaves's recent World Endurance Championship crash, again at Monza's second chicane.

Where the F2 clash was caused by Nissany aggressively pushing Hauger onto the grass approaching the Club chicane, at a trajectory which caused the blameless Norwegian's now three-wheeled machine to vault the kerb into his Halo-protected assailant, Chaves's plight was caused by a brake problem.

The tail of his TF Sport Aston Martin came around and the car slid out to strike the kerb side on, deflecting the car upwards away from the ground at a climbing angle. The energy within the impact was sufficient to rip the door off immediately, but the crash was made even more severe by the floor underneath generating lift.

Any rigid flat surface passing through the air, such that its leading edge is higher than its trailing edge, will deflect the air downwards. Due to Newton's laws we know every action has an equal and opposite reaction, so by return the flat surface is pushed upwards.

This effect with cars can be seen more clearly with a problem that hit the headlines at Le Mans in 1999 when, notoriously, the Mercedes CLR took off three times due to its nose lifting. Peter Dumbreck's car managed to climb so high during the race that the barrier running alongside the track was easily cleared.

The initial reason for the cars starting to take off in these two instances may have been different, but once the air has a clear path onto the underside of the car the effect is the same. Chaves flew with little loss of forward speed, then experienced a second impact as he landed before the Aston rolled and slid to a standstill.

 

Cars that are launched can also have their flight time prolonged by ‘riding’ a cushion of air close to the ground. Ironically this is referred to as flying in ‘ground effect’ in aeronautics, where the term was originated. Given the basic safety benefits intended to be brought about by Combination Kerbs – stopping fast moving cars from passing closer to the barrier than intended – it is equally ironic that through this they can cause a vehicle to travel a great distance with little of the normal loss of speed expected during an accident.

Abbie Eaton's 2021 crash in the W Series at the Circuit of The Americas best illustrates how inherently serious a high energy impact can be. Her car ran over a kerb with enough force to fracture two vertebrae, while at the same meeting Christian Weir suffered similar injuries in the F4 race. Sean Geleal was also hurt in an F2 race at Barcelona in 2020.

"The kerbs are put there to try and limit the track limits, but if it comes at the expense of injuries, potential life-changing injuries, then that's unacceptable"George Russell in 2021

Surely, the consideration of this potential consequence alone must be seen as a key argument against the continued use of Combination Kerbs? A piece of standard trackside furniture that can uniquely cause serious, and potentially life-changing, injury cannot have a viable place in 21st Century motorsport.

As GPDA director George Russell put it in Austin last year: “The kerbs are put there to try and limit the track limits, but if it comes at the expense of injuries, potential life-changing injuries, then that's unacceptable.”

The question is, how does the FIA move forwards if both policing of limits and raised kerbs are failing? Its spokesperson confirms that all of these accidents are recorded and reviewed as a part of the FIA's ongoing safety process. Reassuringly, they also state: “The FIA Circuits Commission and its Track Limits Working Group are actively working on a return to natural deterrents such as grass verges and gravel to discourage drivers from exceeding the limits of the track.

“This is a complex problem though, with a need for any solution to be multi-discipline (single-seaters, touring cars, sportscars, etc), appropriate for both cars and bikes, and take circuit maintenance considerations into account.”

With the high-profile accidents, injuries and a growing movement of dissent within the F1 community regarding ‘sausage kerbs’ on one side, and multiple drivers complaining about the Austrian GP's large number of track limits notifications on the other, this is clearly a problem that the FIA needs to tackle sooner rather than later.

Chaves's Aston Martin was launched by kerbs at Monza, resulting in a huge accident and more questions asked of the FIA

Photo by: Eric Le Galliot