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Wet Pavement Crash Simulations Assist NTSB Study

The HVE White Paper section of the EDC website Library contains numerous examples of real-world crash reconstructions and research studies performed by HVE users from around the world. Each paper highlights the application of HVE to investigate factors that may cause or contribute to a crash.

In this paper, presented by the National Transportation Safety Board (NTSB) at the 2005 HVE Forum, HVE is used to simulate a crash involving an Intercity Bus and an SUV, allowing for a close examination of contributing factors including the wet pavement conditions. Extensive site inspections, physical tests and research were conducted by the NTSB, and friction tests of the bus's tires were conducted at the General Dynamics Tire Research Facility (TIRF). The results of the combined efforts provided a solid foundation for the simulation inputs and supported the final recommendations of the NTSB in Highway Accident Report NTSB/HAR-0502.


HVE-WP-2005-1
HVE Data Inputs Based on Testing for a Wet Pavement Accident Involving an Intercity Bus and an SUV
Lawrence E. Jackson, David Rayburn, Dan Walsh, Jennifer Russert
National Transportation Safety Board

David Gents, George A. Tapia, Vincent M. Paolini
General Dynamics Tire Research Facility

EXCERPT:

On February 14, 2003, at about 10 a.m., a 1996 Dina Viaggio Motor Coach (bus), traveling northbound on Interstate 35, near Hewitt, Texas, lost control as the bus approached the crest of the hill and as the driver approached slowing and/or stopped traffic ahead. The weather conditions at the time of the accident were reported to be overcast with reduced visibility due to fog, haze, and heavy rain. The bus driver stated that the queue of vehicles ahead of the bus in the right-hand lane was longer and closer to him than the queue of vehicles in the left-hand lane and he decided to move into the space available in the left-hand lane. As he did so, the last vehicle in the queue in the right-hand lane also began to move into the left-hand lane. The bus driver braked harder, the rear of the bus skidded, the bus driver was unable to maintain control, and the bus went off of the roadway and into the grassy median. The vehicle crossed the median and entered the southbound lanes of the highway, striking a southbound 2002 Chevrolet Suburban Sport Utility Vehicle (SUV) occupied by a driver and two passengers.



Aerial View of Accident Location (Souce: Texas DPS)


Motorcoach Post-accident Position

This paper will discuss the technique used to simulate a wet pavement accident. It will discuss the weather data, environmental data and the vehicle tire data needed to simulate a loss-ofcontrol using SIMON. Weather data was obtained from the National Weather Service and calculations were made that indicated the surface was flooded based on the rain intensity, pavement texture depth, roadway drainage path length and the cross slope of the pavement.

The surface was documented with an ASTM skid trailer using a treaded and a smooth tire. This data showed that for smooth tires the friction changed both longitudinally every 0.1-mile and laterally between wheel paths, which created a split coefficient of friction. Five of the accident bus's 8 tires were tested at the General Dynamics Tire Research Facility (TIRF), on a smooth surface selected to match the accident site, for cornering and longitudinal friction at different speeds, and with different water depths. The surface used on the TIRF was validated with the ASTM ribbed and smooth tires. The results of these tire tests are presented. Finally, the data inputted for the surface friction factor and the tire in-use factor will be discussed.



Comparison of Physical Evidence to Simulation Tire Marks for the SIMON Bus Approach Simulation


Comparison of Braking with No Steering Simulations at the Accident Site with Various Conditions

To download this publication, visit the HVE White Paper section of the EDC website Library or just click on the images above. For more information about using HVE for your crash investigations, please contact EDC at 888.768.6216.


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