One of the best and most frequently used mechanisms for stopping runaway trucks is the truck escape ramp, particularly the gravel arrester bed. To learn more about the energy-absorbing characteristics of the stone and to develop better design criteria, the Pennsylvania Transportation Institute (PTI) conducted full-scale testing of gravel arrester beds. For this study, PTI constructed two 300-ft-long test ramps, one filled with rounded river-bed gravel and the other with more angular crushed gravel. The data taken included entry speed, stopping distance, accelerometer data, cross-section measurements of the ruts left by the truck tires, and distance-versus-time data. River gravel exhibited greater deceleration forces than crushed gravel. The existing Pennsylvania Department of Transportation (PennDOT) beds at Punxsutawney, Pleasant Gap, and Freeport represented the standard of excellence, showing an average deceleration of 0.516 g. However, test results show that a 36-in.-deep bed gave the same results as a bed that sloped to 8 ft deep. Finally, mounds and crash barrels filled with stone were tested and evaluated.
Abstract