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The timing and associated levels of braking between initial brake pedal application and actual maximum braking at the wheels for a tractor-semitrailer are important parameters in understanding vehicle performance and response. This paper presents detailed brake timing information obtained from full scale instrumented testing of a tractor-semitrailer under various conditions of load and speed. Brake timing at steer, drive and semitrailer brake positions is analyzed for each of the tested conditions. The study further seeks to compare the full scale test data to predicted response from detailed heavy truck computer vehicle dynamics simulation models available in commercial software packages in order to validate the model's brake timing parameters. The brake timing data was collected during several days of full scale instrumented testing of a tractor-semitrailer performed at the Transportation Research Center, in East Liberty, Ohio.

Vehicle dynamics models employed in heavy truck simulation often treat the semitrailer as a torsionally rigid member, assuming zero deflection along its longitudinal axis as a moment is applied to its frame. Experimental testing, however, reveals that semitrailers do twist, sometimes enough to precipitate rollover when a rigid trailer may have remained upright. Improving the model by incorporating realistic trailer roll stiffness values can improve assessment of heavy truck dynamics, as well as an increased understanding of the effectiveness of stability control systems in limit handling maneuvers. Torsional stiffness measurements were conducted by the National Highway Traffic Safety Administration (NHTSA) for eight semitrailers of different types, including different length box vans, traditional and spread axle flat beds, and a tanker.

The ability of a simulation model to accurately predict vehicle response is investigated in this paper. This study seeks to compare full-scale tractor-semitrailer straight-line braking test data to predicted response from a detailed heavy truck computer vehicle dynamics simulation model. The model, Simulation MOdel Non-linear (SIMON), is a vehicle dynamic simulation model within the Human Vehicle Environment (HVE) software environment. This computer program includes a vehicle dynamic model capable of simulating vehicle motion in 3-dimensional environments and includes Brake Designer and ABS Simulation Models. The results of several days of full scale instrumented testing of a tractor-semitrailer performed at the Transportation Research Center, in East Liberty, Ohio are presented.

This paper presents and analyzes braking test data and braking marks for a sport, sport-touring, and cruiser type motorcycle. The best-effort braking tests were performed using three motorcycles, three riders, and three initial speeds. All tests were performed on dry asphalt, with the exception of one set of runs for a sport touring motorcycle on wet asphalt. Three braking strategies were used; front-brake-only, rear-brake-only, and front-and-rear brakes used together. From these data, engineers can evaluate the following effects on braking performance: rider, speed, pavement condition, braking strategy, and motorcycle type. This paper should also serve to assist the vehicle accident reconstructionist in complementing the existing data on motorcycle braking performance.