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44 kinematics of a typical 2000P vehicle traversing different For both scenarios, the truck impacted a 12-m-long instal- types of AASHTO curbs at higher speeds. Due to the physi- lation of AASHTO curbs. The tests were conducted using cal limitations of the testing site, only the low end of the curb types B, C, D, and NY. speed range of interest (60 to 100 km/h) could be tested safely. During these tests, data were collected about the dis- placements and accelerations experienced by the vehicle. Full-Scale Crash Tests of CurbGuardrail The tests were performed using the 1995 Chevrolet C2500 Combinations Cheyenne pickup truck shown in Figure 26. The truck was modified by removing the bed and installing a roll bar, anti- Several full-scale tests were conducted of 2500P trucks rollover outriggers and ballast weights. The final mass of the impacting curbguardrail combinations. The test reports are vehicle, ready to be tested and refueled, was 2,165.90 kg; the included in Appendix I of this report. The impact conditions final mass with fuel and driver was 2,248.00 kg. were similar to NCHRP Report 350 Test 3-11. The follow- The truck was driven toward a 12-m-long curb installation ing articles were tested: at angles of 15 and 25 degrees. Since the test vehicle was controlled by a driver, it was difficult to obtain precise, repeat- · AASHTO Type B curb directly beneath modified G4(1S) able impact conditions. The driver was instructed to follow a guardrail, · AASHTO Type B curb positioned 2.5 m in front of mod- painted line on the testing area and to hit the curbs at 35 mph (15.65 m/s). Due to the runway length available and the vari- ified G4(1S) guardrail, and · New York Type T100 curb positioned 4.5 m in front of ability due to human and vehicle performance, the actual modified G4(1S) guardrail. impact speed varied. After each test, the driver reported the impact speed. Brakes were applied by the driver only after The test vehicles were a 1998 GMC 3/4-ton pickup (test iner- the vehicle had crossed the curb. tial mass of 1,993 kg), 1994 Chevrolet 3/4-ton pickup (test iner- tial mass of 2,002 kg), and a 1989 GMC 3/4-ton pickup (test inertial mass of 2,014 kg). The guardrails tested were 53.34-m Moderate-Speed Live-Driver Nontracking Tests installations of AASHTO SGR04a guardrail with a SEW02a of AASHTO Mountable Curbs End Terminal and Re-Block recycled plastic blockouts made of 50% high-density polyethylene and 50% polypropylene. Nontracking full-scale curb traversal tests were also per- They were installed in dry NCHRP Report 350 Strong Soil. formed at moderate speeds (i.e., approximately 56 km/h) with Figure 28 shows the test vehicle and configuration for the a live driver. The purpose of these tests was to evaluate the curb directly beneath the guardrail. vehicle trajectory and kinematics of a typical 2000P vehicle In each test, the vehicle impacted the curb at approxi- traversing different types of AASHTO curbs in nontracking mately 85 km/h and 25 degrees. The critical impact point mode in order to investigate the extent to which the curbs act was near the midpoint of the guardrail installation, 0.6 m as a tripping mechanism for vehicle rollover. upstream of Post 14 and 2.5 m upstream of a connection These tests were performed using the same 1995 Chevro- splice respectively. let C2500 Cheyenne pickup truck with the same modifica- tions as for the tracking tests. The driver executed two dif- ferent maneuvers resulting in a nontracking impact with the SUMMARY curb. These maneuvers were intended to reproduce two typ- ical scenarios of vehicles running off the roadway, over- Real-world crash data were used to better characterize steering and understeering. safety problems associated with curb and curbbarrier com- In scenario 1, oversteering, the vehicle was accelerated to binations on higher-speed roadways and to provide leads to a constant velocity of 35 mph (56 km/h) in a straight-line tra- the crash testing and simulation efforts conducted in this proj- jectory at a 55 ± 10( angle with respect to the curb line. At a ect. The analyses conducted with crash data included the fol- marked point 6 m before the curb line, the driver turned the lowing: assessment of the extent of the U.S. curb-related steering wheel approximately 45 degrees and immediately safety problem; examination of curb-related rollover risk and activated the emergency brake (i.e., rear brakes only) to nature given a crash; comparison of crash, injury, and roll- break loose the rear end of the vehicle. over rates per passing vehicle for guardrail sections with and In scenario 2, understeering, the vehicle was accelerated to without curbs; curb-crash severity modeling; and examina- a constant velocity of 35 mph (56 km/h) in a straight-line tra- tion of the nature of curb impacts, using crash reconstruction jectory at a 55 ± 10( angle with respect to the curb line. At a data and comparing extreme and nonextreme crashes. marked point 6 m before the curb line, the driver turned the FEA was also used to study the effects of vehicle inter- steering wheel to approximately 60 degrees without applying action with curbs and curbguardrail combinations. The advan- the brakes. tage of computer simulation is that once a model is developed,
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45 Figure 28. Test vehicle and setup for Type B curb beneath guardrail. the impact conditions and the basic geometry of the installa- Full-scale crash tests were used to validate the computer tion can be varied easily. The finite element program LS- models. Live-driver curb traversal tests were performed at DYNA was used in a parametric study to investigate the low and moderate speeds in tracking and nontracking modes. response of vehicles crossing various types of curbs. LS- Several full-scale tests of curbguardrail combinations were DYNA was also used to investigate the effects of installing also performed at higher speeds. curbs in conjunction with guardrail, regarding the ability of the The results of these analyses are discussed in Chapter 5 of barrier to safely contain and redirect an impacting vehicle. this report.