Accident data reconstruction is rarely touched upon by many of the market’s fleet management systems. This post will show you how to reconstruct the data from a vehicle accident to learn more about what happened.
The Accelerometer
The Geotab fleet tracking devices have a built-in accelerometer that measures speed readings in a 3-axis format, including forward/back, side, and up and down movement. This data can then be used by accident reconstruction experts in unision with data collected from the accident site as well as GPS data to learn about the accident.
Fleet Tracking Device Data Storage
Geotab fleet tracking devices can usually store up to 3 weeks of data, including the last 102 minutes of driving data. This is very important for accident reconstruction especially if the accident is preceded by a long time of driving. The memory of the device is divided into 2 sections:
1. Logging data section – which may include 39,936 records
2. High resolution data – which may include 6,120 records
The first section above is regularly uploaded to the client database, which also consists of the acceleromter readings and GPS data. The second section will be uploaded automatically if an ‘accident-level’ threshold is reached.
Auto Calibration
A tracking device that can automatically calibrate with the vehicle movement will ensure that the accelerometer data will be logged, regardless of the orientation at time of installation. In the rare case that the tracking device changes orientation, the Geotab device regularly analyzes the accelerometer readings to automatically re-calibrate. Although, Geotab does a very good job of filtering noise, it is very important to secure the installation to avoid false accident level thresholds, particularly if the device is installed in a storage area of the vehicle where the device can be knocked during package loading.
Tip: If the device up/down g force deviates from 9.8 m/s2 by more than ±3 m/s2, this is a good indication that the device is changing orientation.
Automatic Calibration
A Geotab fleet tracking device will automatically calibrate itself with the vehicle’s movement, assuring that the accelerometer data will be uploaded. Although the device is very efficient at re-calibrating itself, it is important to have it securely fastened in the vehcile for accurate ‘accident-level’ threshold readings.
Note: If the tracking device is positioned up or down,the g force can deviate from 9.8 m/s2 by more than ±3 m/s2.
Accident Threshold Tuning
In order to fine-tune the accident threshold, Geotab hired a stunt driver to conduct a controlled collision environment. Several accident scenarios were conducted to ensure that the most valuable data can be captured with the least amount of cellular data usage. The results of the collision are shown in the graph above. The impact triggered an accident level threshold in Geotab’s GPS fleet management software, with a change in acceleration of nearly 38 m/s2.
Note: A Geotab device will report an accident level event if there is a change in acceleration of at least 24.5 m/s2.
Accident Thresholds
Geotab’s research into their devices included testing them in controlled collisions, where the accident thresholds of the devices were fine-tuned. The results of a recent collision test are shown in the above graph, where the impract triggered the accident level threshold in the Geotab fleet managemetn system since it had a change in acceleration of almost 38 m/s2.
Note: Accidents are reported in Geotab fleet management software if change in accelerations are at least 24.5 m/s2.
The graph above is based on a 5 km/h vehicle impact into a median (by a professional stunt driver). The vertical axis is shown in units of 9.8 m/s2, and the horizontal axis is in seconds.
A fleet tracking device will not only improve the safety of your drivers by changing their behavior and habits through vehicle driver feedback, it will also ensure that you have reliable information about the accident quickly.
Happy Tracking,
Russ Salo, President
GPS to GO, now you know
