Many commercial Telematics and Insurance Telematics solutions capture accelerometer data to calculate Driver Behaviour reports and automatic alerts in the event of a possible collision.

This data is valuable in determining a vehicle’s activity up to a collision point or its driving behaviour on the journey leading to the collision.

In simple terms, the accelerometer is a sensor mounted in the telematics hardware that records the levels of acceleration and deceleration, forward/backward movement (X), lateral (Y), left and right movement, and vertical (Z), up and down, movement, known as XYZ values.

The accelerometer sensor will provide a reasonable indication of the level and direction of any impact in a collision or style of driving behaviour based on acceleration and deceleration. The accuracy depends on the installation of the Telematics unit securely to a vehicle chassis, the quality of the sensors, and the detection rate.

Accelerometer data usually measure force in milliG. G, observed on the earth’s surface and accelerates at 9.81 ms^-2. In telematics and collision investigation terms, braking above 2.5g is considered “harsh.” X and Y accelerometer data can be converted into ms^-2, providing a speed value for detailed analysis.

In any analysis, the aim is to match XYZ value with location data to provide a detailed record of a vehicle movement with acceleration and deceleration, especially where any value would indicate a harsh braking event or possible impact.

The frequency of the X, Y, and Z data records depends on the type of vehicle tracking unit. Some may only record the X, Y, and Z values when a GPS location is recorded, possibly only every 10, 15, or 30 seconds. The exception is if a possible impact of a G force more significant than 2.5G is detected. Not all Telematics units use the same values to decide if a sensor value indicates a “harsh braking” or possible impact event. Some more fully functional Telematics solutions will also provide additional data in a crash file that contains second by second, up to 45 seconds pre-impact and several seconds after impact, allowing a more detailed collision analysis.

XYZ data in collision analysis is vital to an accurate record of what happens when deceleration starts, potentially a driver’s initial reaction to an incident, speed leading up to impact, and the force of impact.

Without XYZ data, it is still possible to estimate the G forces from speed changes ( initial and final velocity )  and time and distance travelled, but the level of accuracy is reduced.