EARTH-BERM VEHICLE DEFLECTOR

In an attempt (limited) to provide factual information that could be of assistance toward rationalizing the selection of earth-berm configurations as safety elements in the highway system, a modified version of the Highway Vehicle Object Simulation Model (HVOSM) was used to investigate vehicle behavior on earth-berm slopes. Rigid-body mechanical equations were also used to predict vehicle paths. Details are noted of the initially assumed operating conditions for the computer simulations as well as of additional simulations. The results of computer simulation analysis led to the selection of a berm with a slope of 1.2:1, a height of 12.5 ft, and a length of 250 ft for construction and full-scale testing. Two criteria were used to judge the capability of the earth-berm slopes to safely restrain or redirect traversing vehicles: vehicle rollover and vehicle accelerations tolerable to humans. Five full-scale lists were conducted using a 1963 Ford Galaxie similar to the vehicle used in the computer program. The results showed that the peak and average accelerations (g's) that occurred when full-scale vehicle impacted 1.2:1 earth-berm slope and the length of berm traversal were in good agreement with those predicted by the HVOSM computer simulation. The vertical height of vehicle climb was about twice that which was predicted by computer; two unpredicted rollovers also occurred. Relatively simple rigid-body equations that neglected friction between the vehicle and the slope surface and assumed the vehicle mass to be concentrated at a point showed promise as a means for estimating the height of the vehicle climb and the length of the slope traversal. It was concluded that although very steep slopes (1.2:1 and steeper) are not appropriate for earth berms it is recommended that this research approach be applied to further studies in the field.

• Record URL:
  • http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rrd_77.pdf
• Supplemental Notes:
  • Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved.
• Corporate Authors:

  Transportation Research Board

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  Washington, DC  United States  20001
• Publication Date: 1975-8

Media Info

• Media Type: Digital/other
• Pagination: 3 p.
• Serial:
  • NCHRP Research Results Digest
  • Issue Number: 77
  • Publisher: Transportation Research Board

Subject/Index Terms

• TRT Terms: Berms; Computer programs; Constraints; Deflection; Earth; Equations; Forecasting; Highway design; Highway safety; Mechanical acceleration; Rollover crashes; Simulation; Testing; Vehicle dynamics; Vehicles
• Uncontrolled Terms: Vehicle path
• Old TRIS Terms: Constraining; Traverse computations
• Subject Areas: Design; Highways; Marine Transportation; Operations and Traffic Management; Safety and Human Factors; Vehicles and Equipment;

Filing Info

• Accession Number: 00127883
• Record Type: Publication
• Contract Numbers: 20-7, Task 3
• Files: TRIS, TRB
• Created Date: Apr 21 1976 12:00AM