The agreement is a result of recommendations made in the new national Road Death Investigation Manual, which Thames Valley Police has just adopted, designed to ensure a consistent standard of investigation into police-related road deaths.

The agreement allows for direct 24-hour consultation access with a TRL expert, who will then determine whether the immediate attendance at the scene by a TRL investigative team is required.

Inspector Malcolm Collis, head of roads policing at Thames Valley Police, said: "TRL will provide a truly independent and neutral investigation.

"This is an opportunity for us to work more closely with them and gain from their expertise. They may well be asking us difficult questions but it is only right and proper that we are held to account for our own actions."

He said that most forces had independent investigations carried out by officers from other areas, but added: "The drawback with having reciprocal arrangements with other forces is that we would have an obligation to investigate similar incidents in other force areas, which could take a team of officers away from their duties in Thames Valley.

"Although we will have to pay for TRL investigations, the cost represents very good value when compared to the potential costs involved in losing officers for considerable amounts of time out of the force.

"This agreement will provide expert knowledge in the investigation of collisions and satisfy the need to be open and transparent when investigating our own serious collisions.

"Although we have drawn up a very sound set of procedures and protocols with TRL our sincere wish is that we do not have to implement them very often.

"But when unfortunately we do, we know the public can be confident that we are taking it seriously."

TRL is one of the world's leading centres of excellence in the field of transport research. It covers a wide range of topics including setting standards for highway design and management, undertaking vehicle impact testing, and studying the effects of alcohol and fatigue on drivers.

TRL also attends and investigates traffic collisions for a wide range of organisations and as part of its research programme for the Department for Transport.

Paul Forman, TRL's head of Investigation and Risk Management, said: "We are delighted to be working with Thames Valley Police and being able to use our scientific expertise in this way. Obviously, we hope that such incidences will be few and far between, but the police can be confident that the service we provide will be truly impartial and comprehensive."