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Understanding acceleration, braking and cornering in MyGeotab

Published on September 16, 2021 in Driver Safety by Frankie Van Puyenbroeck |  2 minute read

Learn how to make improvements to your harsh acceleration, braking and cornering rules in MyGeotab.

Are you noticing discrepancies in your data? Do you work in the public sector, or haul fragile cargo? If the answer is yes to any of these questions, you probably need to make improvements to your harsh acceleration, braking and cornering (ABC) rules. Read on to learn more about ABC rules and why they are important.

When are ABC rules triggered?

ABC rules are triggered when the gravitational force (g-force) threshold is met. You can view and edit this setting in MyGeotab by going to Rules & Groups > Rules from the main menu. 

Rules & Groups menu

Rules & Groups menu 

Rules menu screenshot

Customisable Harsh Braking, Hard Acceleration and Harsh Cornering exception rules in MyGeotab  


When setting up your database, Geotab recommends starting in the middle of the specific vehicle class and adjusting when needed based on fleet objectives and the unique aspects of your fleet. 


As the slider moves from left to right through all the vehicle classes, the monitoring becomes more sensitive. When the slider is set to the least sensitive setting for passenger vehicles (far left), it is using the most lenient monitoring and only the most aggressive events will trigger driver feedback.

Read Geotab’s product guide to learn more.

Why do I need to set ABC rules for each vehicle type?

Geotab monitors possible ABC events through the Geotab GO device. The amount of g-force registered in the Geotab GO device during an ABC event is associated with the g-force on your vehicle, and uses sharp changes in accelerometer data to infer vehicle events such as harsh cornering. 


You may have discrepancies in your data due to incorrect ABC settings. Symptoms of this in your database may be that you see too many or too few rule violations, in this case you will need to use your ABC sliding scale to create specific rules for each vehicle. It is recommended that after making changes to a rule, collect the data and monitor your new settings for at least one to two weeks before determining if the setting works for you. 

Different types of vehicle classes

In MyGeotab, vehicles are grouped into three classifications for the purposes of driver feedback settings: 

  • Passenger Car refers to passenger vehicles.
  • Truck/Cube Van includes larger delivery vans, and light rigid trucks
  • Heavy-Duty refers to larger rigid trucks and prime movers.

Larger, heavier vehicles should use lower g-force values as they must take slower turns for safety. Since extensive testing has revealed that these different classes of vehicles react to g-forces differently, the sliding scale allows you to customise the feedback precisely for each vehicle in your fleet.

All fleets are different 

Ask yourself the two questions below to help determine what your ABC sensitivity should be.


What sector are you working in? 

Different sectors have different driving objectives. For example, to closely monitor an ambulance carrying a paramedic and patients, you would increase the sensitivity for ABC events than that of a delivery truck carrying paper towels. Think about what speed is appropriate for your vehicles to be driving in and set the rules accordingly.


What type of cargo do you carry? 

If your fleets are hauling fragile cargo, you may want to consider editing your ABC rule sensitivity and turning on driver feedback to prevent breaking the cargo you are moving. That way, if a driver begins to drive corners too quickly or brake/accelerate too harshly, they will be alerted. 

We recommend fleet managers monitor the readings and adjust sensitivity based on their real-world experience.

Analyse driver behaviour

The data collected through proper implementation of your ABC rules will provide insights into your drivers’ behaviour. If you have a safe driver who gives themselves the proper distance to brake, slows down to turn and takes their time during acceleration, you will see this reflected in your driver safety scorecard


Not only is safety a factor when analysing driver behaviour, but hard acceleration, braking and cornering also negatively impacts fuel economy on the highway and wears out your vehicles quickly.  


To learn more, visit the Fleet Success Center on the Geotab Community. 

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Geotab's blog posts are intended to provide information and encourage discussion on topics of interest to the telematics community at large. Geotab is not providing technical, professional or legal advice through these blog posts. While every effort has been made to ensure the information in this blog post is timely and accurate, errors and omissions may occur, and the information presented here may become out-of-date with the passage of time.