Heavy Truck Braking

Topics related to Vehicle Specifications, Vehicle Acceleration Tests, Vehicle Braking Tests
MSI
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Heavy Truck Braking

Post by MSI »

Some reports on Truck braking tests, with, and without ABS:
  • 2010:The Effectiveness of ABS in Heavy Truck Tractors and Trailers
    • Federal Motor Vehicle Safety Standard No. 121 mandates antilock braking systems (ABS) on all new air-
      braked vehicles with a GVWR of 10,000 pounds or greater. ABS is required on tractors manufactured on
      or after March 1, 1997, and air-braked semi-trailers and single-unit trucks manufactured on or after March
      1, 1998.

      The primary findings of this report are the following:
      - The best estimate of a reduction by ABS on the tractor unit in all levels of police-reported crashes for
      air-braked tractor-trailers is 3 percent. This is based on data from seven States and controls for the age of
      the tractor at the time of the crash. This represents a statistically significant 6-percent reduction in the
      crashes where ABS is assumed to be potentially influential, relative to a control group, of about the same
      number of crashes, where ABS is likely to be irrelevant.
      - In fatal crashes, there is a non-significant 2-percent reduction in crash involvement, resulting from a 4-
      percent reduction in crashes where ABS should be potentially influential. The age of the tractor at the
      time of the crash is not important. Rather, external factors of urbanization, road speed, and ambient
      lighting are influential and are accounted for in the final estimate.
      - Among the types of crashes that ABS influences, there is large reduction in jack-knives, off-road over-
      turns, and at-fault involvements in collisions with other vehicles (except front-to-rear collisions).
      Counteracting are an increase in the number of involvements of hitting animals, pedestrians, or bicycles
      and, only in fatal crashes, rear-ending lead vehicles in two-vehicle crashes.
  • 2010: Full-Scale Testing and Analysis of Tractor-Trailer Braking Performance With and Without Trailer Anti-Lock Brakes SAE Paper 2010-01-1891
    • Anti-lock brakes have been implemented on tractor-trailer units for several years. However, a fatal accident involving trailer swing indicated that there is some disagreement within the accident reconstruction industry as to what effects trailer anti-lock brake systems have on the stopping performance, dynamic performance/handling of the trailer, and resultant skid marks left on the roadway. Full-scale testing was conducted on a tractor-trailer unit which was equipped with anti-lock brakes on both the tractor and trailer. Full application braking tests were performed from 65-70 mph concurrent with a lane change. Baseline tests were conducted with all anti-lock systems operational, and the tire marks, amount of trailer swing, and stopping distance were recorded. The test was then repeated with the trailer anti-lock brakes disabled. All tests were videotaped from three positions: a stationary camera at the end of the test run, a stabilized camera mounted on a chase vehicle, and a stabilized camera mounted on the driver's side of the tractor cab facing aft. Results showed the types of marks left by tires both with and without anti-lock brakes. The tests also provided qualitative indications as to the effect of locked trailer tires on trailer swing. The measured stopping distance was also used to calculate an overall deceleration rate for the tractor-trailer, and this deceleration rate was then compared to speed-time data recovered from the tractor's engine control module.

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