AITrucks Brake Efficiency

 AITrucks Brake Efficiency Module was the first commercial computer program to provide the collision analyst with an objective method of calculating the braking efficiency and stopping distance of vehicles fitted with S-cam air brakes.

The program will evaluate the performance of each brake with straight forward and simple measurements.

The program can also predict the braking performance of the vehicle subject to conditions different than those found at the time of the inspection. The analyst can assess the potential braking performance of the rig, for example, with hot brakes, under different weight conditions, with different brake components fitted, or with the brakes in different adjustment. See AITrucks Brake Efficiency Sample Screens.

Click here to view a Brake Efficiency sample report.


The calculation model enhances research performed by Mr. Ronald B. Heusser, formerly of the National Transportation Safety Board and now an independent consultant. Mr. Heusser expanded the work done by the National Highway Traffic Safety Administration's Vehicle Research and Test Center and consolidated it into a procedure to compute deceleration rates.

The calculation model takes the measured or assumed stroke and air pressure and the brake chamber size and calculates the pushrod force. This pushrod force is used with other vehicle data including the brake drum radius, tire rolling radius and lining friction coefficient in a modified brake sizing formula to predict the brake force. This calculated braking force can then be compared with the braking force required to lock the wheel. The model considers dynamic stroke and temperature effects on the air brake system.

The model is fully developed and explained in the User's Manual to allow the user to duplicate the results by hand.


Data entry into the program is easy. Defaults are provided for all data, so only differences need to be explicitly entered. A sample brake data table is shown for reference. The following information is required for each wheel of the vehicle:

  •  Brake in use?
  •  Rolling radius of tire
  •  Brake chamber size
  •  Brake drum radius
  •  Slack adjuster length
  •  Brake lining friction coefficient
  •  Measured stroke
  •  Weight on wheel
  •  Air pressure to chamber
  • Support for the most common clamp type chamber sizes in use today.
  • Support for rigs with from two to twelve axles.
  • Define defaults for air pressure, lining friction, and S-cam radius to speed data entry.
  • Weights can be entered by axle or individual wheel.
  • Any brake can be specified as non-functional.
  • Pushrod force is calculated and displayed.
  • Results include overall braking efficiency and effective drag factor.
  • Automatically calculates the stopping distance and time based on a user-specified road drag factor and initial speed, and the calculated braking efficiency.
  • Braking force on each axle set is displayed on the graphic image of the rig to show imbalances and potential for control problems.
  • Calculates forces at each break group with display of rotational tendency.
  • Comprehensive User's Manual contains the formulas used by the program to enable the reconstructionist to calculate the same results by hand to prove the results for court.
  • Software developed and supported by experienced professional engineers who are practicing collision analysts.

The requirements to run ARSoftware programs are limited but important. The software requires a computer running a 32-bit version of Windows. In addition, you will need a mouse or other pointing device. The software is compact enough that there are no practical memory or storage requirements. The software can be operated in a network environment but is licensed to an individual.

Additional Information