Lisa Marie Bowen · Prevention of Future Deaths report

I commenced an investigation into the death of Lisa Marie Bowen. The inquest concluded on the 1st August 2025 when I found that the medical cause of death was:

Ia Traumatic Head and Spinal Injuries

and my conclusion as to the death was:

Road Traffic Collision

I subsequently held a hearing, on the 6th November 2025, to receive evidence relating to the prevention of future deaths.

On the morning of the 11th January 2022, Lisa Bowen was driving her Toyota Corolla motor car on the M25 motorway when its rear offside tyre deflated. A tyre deflation warning light probably appeared on the dashboard, but it was not possible to ascertain whether Ms Bowen saw it and, if she did, whether or how she responded. She drove on for at least several miles, as a result of which the tyre was damaged and its tread and parts of its sidewalls detached.

Following the tyre detachment, Ms Bowen braked, indicated, and moved on to the hard shoulder. Once on the hard shoulder, she pressed the brake pedal a further five times, with increasing force, but this did not result in any significant reduction in the Toyota’s speed. In consequence, the vehicle did not stop prior to colliding into, and under-running, the rear of a lorry which was present and stationary on the hard shoulder. The Toyota’s speed at the time of the collision was 37.9 miles per hour. The collision occurred 17 seconds after the tyre detachment and ten seconds after the Toyota moved on to the hard shoulder. The collision caused catastrophic damage to the Toyota and, as a result, Ms Bowen suffered fatal injuries and died instantaneously.

If the brakes had worked effectively, there would have been time and distance for the Toyota to have stopped before the collision. The brakes did not work effectively because, when the brake pedal was pressed, the vehicle’s anti-locking braking system was activated, and it operated to reduce the braking effect almost entirely.

The anti-locking braking system was working in accordance with its design.

The outcome was an unintended effect of the system’s design which arose because the specific scenario, of tyre detachment occurring whilst the vehicle was being driven, which was thought to be a rare occurrence, had not been taken into account in the design process.

My full findings are set out in the Findings and Conclusion document which is sent with this report.

Concern 1

As stated above, the brakes on the Deceased’s Toyota Corolla did not work effectively because, when the brake pedal was pressed, the vehicle’s anti-locking braking system was activated, and it operated to reduce the braking effect almost entirely. At the inquest I heard evidence that:

(i) Following the tyre detachment, the speed of the wheel with a detached tyre was much higher than the speed of the three other wheels with undamaged tyres.
(ii) The anti-locking braking system recognised this differential in speed, but perceived that the problem lay with the three slower wheels and assumed that they had locked or were at risk of doing so.
(iii) Consequently, each time the brake was applied, the anti-locking braking system immediately released the braking pressure to the three slower wheels in order to avoid them locking, thereby prioritising the preservation stability and steerability over braking.
(iv) In this way, the anti-locking braking system was working in accordance with its design.
(v) The system was unable to recognise that the problem in fact lay with the fourth wheel which was rotating much more quickly than the other wheels because its tyre had detached.
(vi) The outcome was an unintended effect of the system’s design which arose because the specific scenario, of tyre detachment occurring whilst the vehicle was being driven, which was thought to be a rare occurrence, had not been taken into account in the design process.
(vii) Testing of anti-locking braking systems and braking performance, following a tyre detachment, is not undertaken by the industry as a whole and, therefore, relevant data is not collated.

At the inquest and PFD hearing I was informed that –

(i) A large number Toyota Corolla motor cars continue to be driven on the roads of the UK with the same anti-locking braking system as was in Ms Bowen’s vehicle.

(ii) Anti-locking braking systems are developed by a small number of specialist companies and it may well be that other vehicles currently on the roads of the UK have systems similar to that in Ms Bowen’s car.

(iii) The company which developed the anti-locking braking system used in Ms Bowen’s car (Advics) has since developed and improved its system so that it is better able to recognise if one wheel speed is so different from the others that the data from that wheel should be ignored as unreliable. However, the improvements are not foolproof, not least because acceleration or deceleration of the vehicle affects this function.

(iv) The anti-locking braking system now used in Toyota Corolla motor cars has been developed by a different company (Bosch) and it is not known by Toyota precisely how it would respond following a tyre detachment whilst the vehicle is being driven.

(v) It seems that relevant regulations concerning anti-locking braking systems do not address or specify requirements relating to the scenario faced by Ms Bowen.

Although the detachment of a tyre whilst a vehicle is being driven is thought to be a rare occurrence, I am concerned that that may not be the case and that if it were to happen again, in the same or similar circumstances, the risk of future death continues.

Concern 2

This concern relates to the catastrophic failure of the under-run protection bar (“the Device”) that was in place on the piece of the lorry with which Ms Bowen collided. At the inquest I heard and accepted expert evidence which established that:
(i) The Device was compliant with all relevant regulations and legal requirements, save only that fixing bolts of an incorrect strength had been used to attach it to the lorry’s chassis.
(ii) The strength of the Device was grossly insufficient, either to have prevented any underrun, or even to have reduced the extent of the Toyota’s under-run.
(iii) The Device would not have been strong enough to do so even if the correct fixing bolts had been used.

One expert stated that he was aware that some under-run protection devices are capable of providing protection against much greater forces than is currently required under the law and he expressed disappointment that the relevant legislation and regulations are not more robustly framed, so as to require the use of these much stronger devices.

I am concerned that, in the absence of more stringent requirements in relation to the degree of force that an under-run protection device should be capable of withstanding, a risk of future death arises.