When is EDR data useful? - Expert Witness & Investigations Services

Seatbelt determination

EDR data can assist with cases where it is important to determine if a seatbelt was being worn at the time of a collision. Historically, this type of investigation involves a physical examination of the seatbelt to identify the presence of the tell-tale signs of seatbelt wear, or to help a biomechanics investigation looking at injury causation. The introduction of EDR data will add another important data source to determine if the seatbelt was worn.

The EDR will capture the following information which can be helpful in seatbelt determination cases; seatbelt status for the driver and front seat passengers and whether the pretensioners were deployed. Using the information relating to the seatbelt status can help understand whether the seatbelt was plugged in, although this will not confirm whether the seatbelt was being worn correctly. This is where physical forensic evidence and occupant injury information can help.

Being aware of the existence of this data and its potential benefits in seatbelt determination cases will be invaluable as more and more vehicles on the UK roads record EDR data.

Reaction times and braking

Understanding how quickly a driver reacted to an event is key in many investigations. Often, investigators rely on published research and/or hypothesise about the likely reaction time of a driver. Having access to EDR data can sometimes help in determining a more accurate reaction time for the driver. In cases where a pedestrian steps out from behind a parked car, for example, the time in view is often calculated. Using this, investigators can “start the clock” for the driver’s perception response time; and, through the use of EDR data, determine the point at which the brakes were applied, thereby “stopping the clock”. This may help the Court in determining whether a driver was slow to react to an unfolding event, or whether they reacted appropriately.

Low-velocity impacts

The evidence in low-speed impacts can be subtle and variable, meaning that it is sometimes difficult to determine impact speeds, and resultant changes in velocities experienced by the occupants. Conventional collision reconstruction methods work well above 20mph. In higher speed events tyre marks may form on the road, should the drivers have performed emergency braking. When documented, the tyre marks assist in calculating pre-impact travel speeds. However, in low-velocity collisions, tyre marks are rarely identified, and even then, they tend not to be recorded or measured.

EDR data will add another important data source for determining velocities in low-speed collisions. In cases where the vehicle has experienced only small changes in speed, EDR data may not be captured, this can be valuable information in helping to determine that the impact must have occurred at less than the minimum activation threshold of 5mph.

Multi vehicle collisions

In slow moving traffic, rear-end collisions are inevitable. It is sometimes the case that a driver will allege they were struck from behind by another vehicle which caused them to collide with the car in front. This presents a conflicting picture when determining liability; thankfully EDR data can help. From the crash data captured when the device records an incident, it is possible to determine the direction from which the original collision occurred. This is achievable through a detailed analysis of the acceleration data and allows investigators to determine, with a good degree of accuracy, whether a frontal or rear impact occurred first.

There are many more incidents where EDR data can be useful, but the best approach is to contact our Investigations Team for advice regarding the likelihood that EDR data could assist your case.

This is the third bulletin in a series of information notes about EDR. The others in the series cover