Electronic Stability Control and its Impact on Speed Analysis from Yaw Marks

Author(s): Wright

Slidedeck Presentation:

8C - Wright.


Since 2012, electronic stability control (ESC) has been a mandatory component of all passenger vehicles sold in Canada. This technology is designed to assist a driver regain control of their vehicle when they lose lateral stability.

Some have called ESC 'Anti-Yaw' technology. This terminology is misleading. The ESC system is not predictive rather the vehicle must recognize a loss of lateral stability before ESC activates to regain control.

Electronic Stability Control changes the characteristics of tire mark evidence traditionally used for critical speed (yaw) analysis.

Since 2014, members of the OPP's Collision Reconstruction program have conducted research to better understand the impact of ESC on traditional critical speed analysis methods. Assess the accuracy of measuring protocols currently used to calculate critical speed from yaw marks.

Identify reliable alternatives to traditional measuring methodology for accurate speed analysis from ESC yaw marks.

Find areas of sensitivity and assess the level of accuracy of measuring methodologies. Numerous yaw tests have been conducted throughout Ontario and at the PMG testing site in Blainville Quebec. Testing has included multiple vehicle makes and models with and without out electronic stability control.

Each vehicle was instrumented with Vericom and Racelogic accelerometers . Each test was captured on multiple video recording and speed measuring devices.

All yaw marks were documented using the traditional measuring techniques. Two chord and middle ordinate measurements were taken in the early portion of the yaw mark and used to determine the radius at different positions along the yaw mark.

The yaw marks were also documented using a Sokkia total station. The data was then imported into a computer aided drawing (CAD) program for analysis. All yaw marks were drawn to scale in the CAD program and different methods were used to determine the radius of each mark.

As testing progressed, different approaches were incorporated into the process of yaw mark measuring to evaluate the most reliable means of speed analysis.

The coefficient of friction was determined from skid tests and measured using a Vericom VC4000DAQ accelerometer. Yaw tire marks created by vehicles equipped with ESC demonstrate discernable characteristics that differ from traditional Yaw marks.

Traditional methods for measuring yaw marks have limitations when measuring tire marks from ESC vehicles for speed analysis.

Modifications to traditional measuring protocol enable the investigator to accurately assess the speed of the vehicle as it entered yaw with ESC. none at this time Motor vehicles equipped with ESC will create identifiable tire mark evidence. The characteristics of ESC yaw marks differ from traditional yaw marks.

Speed can be accurately calculated by adapting measuring techniques used for traditional yaw marks.