The Accuracy of Speed Recorded by an SDM and the Effects of Brake, Yaw and Other Factors

Many late model General Motor vehicles include an event data recorder (EDR) that is incorporated into the air bag system sensing and diagnostic module (SDM). Pre-event speed is included in the data collected by the EDR. This study tests the accuracy of the vehicle-reported speed during acceleration, coasting, braking and yaw at speeds between 1 to 90 mph. The accuracy was also tested during heavy acceleration, when an undersized spare tire was mounted on the drive axle and with tires having new and worn tire tread depths. The vehicle-reported speed was compared to the speed measured by a calibrated global positioning system (GPS) speed measuring system. The results showed that the vehicle-reported speed matched well with the GPS speed measuring system during acceleration and coasting, but underestimated the speed during a yaw event and braking. Findings also show that antilock brake system operation will cause the vehicle-reported speed to be underreported. These results indicate that information downloaded from a SDM after an accident can be used in conjunction with conventional methods of accident reconstruction to evaluate the event.

  • Availability:
  • Authors:
    • Reust, Timothy J
    • Morgan, James M
  • Publication Date: 2006-6


  • English

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Filing Info

  • Accession Number: 01044719
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Mar 15 2007 1:04PM