How Are The Police Using Gps And Speed Sensors To Help With Collision And Accident Investigations

One of the most important activities of Road Policing occurs when there is a fatal or life-threatening road traffic collision on the network. In such instances, the Police are required to investigate the circumstances to the highest possible standard: a thorough investigation process is necessary to ensure that all the legal obligations are met, and that every last piece of evidence is efficiently gathered for any due criminal process that might follow. Generally the Police will have a limited time-frame in which to gather all the necessary evidence, as it is important to re-open the road network as soon as possible: however, there is a fine line to be drawn between re-opening carriageways for the convenience of the motorists, and ensuring that no piece of evidence is overlooked.

The Police use incident scene surveying equipment during collision investigations to collect comprehensive surveys of the scene, which can then be effectively used in all legal hearings, from Coroners and Criminal Courts to Civil Litigation Hearings. This equipment measures the angles between points using GPS and speed sensors: this data is then downloaded and converted into a scene diagram. GPS enabled equipment is especially useful as it is both quick to use and extremely accurate, thus avoiding the need for extensive road closures. Research has shown that the use of GPS and speed sensors at collision investigations can speed up survey times by as much as 5.6%.

GPS technology is constantly evolving: each innovation only serves to make crash and collision scene investigation ever more accurate. The latest range of GPS-enabled instruments to be adopted by Police Forces makes collision investigation simpler and quicker. These instruments are used for measuring and recording speed, deceleration, co-efficient-of-friction and Skid-to-Stop testing. A total of 18 of the Police Forces in England, Wales and Ireland now use these state-of-the-art instruments and more will no doubt follow.

The latest instruments offer several advantages over more traditional skid testers and decelerometers that have previously been used by Police Collision Investigators (PCIs). Because the next generation speed sensors with advanced GPS technology have Dual and Tri-axis accelerometers built-in, they are able to measure not just the vehicle Skid-to Stop and Road Friction co-efficient, but also vehicle accelerations to set speeds, between set speeds and also over-time and over-distances which are set by the user. The very latest technology incorporates many additional functions like forward and lateral acceleration measurement, instant viewing of the test results and a large data memory.

In addition to the standard braking and acceleration testing, some Police Forces are also using data acquisition models to undertake more complex testing functions, such as Air and Hydraulic Brake pressure recording on HGVs and LGVs to determine the effectiveness of the braking system. Up to 12 additional speed sensors may be connected to the latest models to allow data to be recorded simultaneously with the braking parameters.

Another important feature of the latest speed sensor technology is the Run Duration Protocol (RDP) function. Many deceleration testers measure the deceleration from a typical minus 0.2G falling trigger point, through to a rising minus 0.2G stop point. Unfortunately this will not give wholly accurate test results as the measurement should stop when the vehicle speed is zero, not the minus 0.2G rising point. This can leave a considerable room for error in the calculation of deceleration, speed and distance, because the data used was inaccurate. By using the RDP function, Police Collision Investigators can be confident that their test data is completely accurate, which is vitally important, should the case proceed to court.

By: Jason H Walker