What happens when a vehicle hits a pothole or rut at high speed?

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MSI
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What happens when a vehicle hits a pothole or rut at high speed?

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Q: Are there formal studies done on what happens when a vehicle hits a pothole or rut at high speed on a wet road? What would happen to steering control, direction and speed of the car? Additionally, rain had washed some sand and soil from the roadside into the pothole.

A: Your question includes 2 components:
  • A vehicle encountering a rut or pothole, where the actual depth of the rut or pothole may be altered by the presence of sand and soil.
  • A vehicle encountering a roadway disturbance with reduced friction (wet roadway)
Some of the HVOSM validation studies and research were on rough roads and in-climate weather.
  • Raymond R McHenry invented the HVOSM during our years in Buffalo, New York, the bad weather capital of the United States
    • Buffalo is not the 'bad weather capital', however i recall during my 21 years there a lot of rain, snow, sleet and POTHOLES! And let me add that I LOVE BUFFALO! It is a great city!
    Some of the HVOSM testing as part of validation were simulations of measured full scale tests on rough roads. In addition to the ability of HVOSM to model any type of terrain a 'rough road' option which was also added as part of the program.
When a vehicle encounters a pothole the wheel or wheels drop into the hole (depending on depth, size, etc.) and then wheel or wheels encounter the back of pothole or rut and pop back up to the roadway level.
  • Some important factors:
    • Measurement of the size and depth of the pothole or rut relative to the wheel size, wheel travel and bumper height.
      • Suspension and tire damage can occur if the pothole or rut is of sufficient size and depth.
    • The pothole or rut may cause a drag on the wheel or wheels which may produce a heading change
      • I say may because the duration of the disturbance is so short it sometimes does not cause any change in heading.
    • Speed and driver attention, perception and response time to steer and brake to counteract the disturbance that the pothole or rut caused is an important factor.
      • Driver response over-reaction to the disturbance (sound, noise, perhaps it made them drop their phone!) may also produce a control loss particularly if high speed and over-reaction is involved.
    • Suspension damage and/or the tire deflation may produce some disturbance to the vehicle.
    • You also mention high speed and wet road:
      • Speed and a wet road may complicate the situation since the wet road reduces the available fiction available for the vehicle to produce side forces to respond to any steering and braking of the driver in response to the pothole/rut disturbance.
    • You also mention the presence of possible sand or dirt in the pothole or rut.
      • That might reduce the depth and disturbance of the pothole and rut and may be hard to quantify depending on how well the situation was documented at the time of any accident.
SUMMARY: So in my long winded (or is it long typed?) response to your question is that there have been many tests of vehicle responses to roadway disturbances:
  • A good starting point is the 1977 report INFLUENCE OF ROADWAY DISTURBANCES ON VEHICLE HANDLING by Klein, Johnson & Szostak, of System Technologies.
  • You also should search the Transportation Research Board site for collections of papers on Roadway disturbances (which that prior paper was also published). The TRB have annual conferences from which collections on topics include summaries of current research on roadway design some of which include documentation of tests of vehicle responses to roadway hazards such as ruts, potholes and wet roadway conditions.

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