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Construction of a transient model for a Class 8 tractor-trailer negotiating mountain terrain is presented. Four basic brake models for free and forced cooling (GSRS, UMTRI, Limpert, and HVE Brake Designer®) are converted to consistent units. The units have been reduced to those accepted variables in the thermodynamic/heat transfer literature (hc, A, cp, M), thereby facilitating model comparison and coefficient selection from the published literature. The data has been compared to real test published data. The effect of varying the desired vehicle speed, vehicle weight, number of adjusted brakes, and slope magnitude on brake drum temperatures is explored.

Information stored in the electronic control modules (ECM) of modern class 8 tractors is a valuable tool to accident reconstruction, but must be properly interpreted. The stored ECM speed data is driveshaft speed. To determine the road speed, the investigator must determine if braking occurred. The level of braking can be estimated from the data and computation of the road speed from the driveshaft speed can be performed by estimating the tire slip. Failure to determine the road speed can result in substantial error in velocity and travel distance estimates. Using realistic models it is shown that proper numerical integration techniques will produce negligible error in highway speed braking distances.

Cargo load movement in cylindrical tanks is incorporated into the static roll model (SRM) implemented in Microsoft® Excel. A “generalized ellipse” equation allows a variety of cylindrical tank profiles to be analyzed. For a partially filled tank, the locus of the cargo center of gravity (CG) locations is determined as a function of the cargo surface slope. The cargo is then modeled as a single point mass that moves along a curved guide shaped as the obtained CG locus in the vertical plane. The cargo CG location is determined iteratively in a Visual Basic routine that surrounds the current Microsoft® Excel based solution technique thereby creating a transparent solution approach for the user.

This paper describes a practical and efficient approach for determining complete transient, as well as steady state response of tractor-trailer air brake systems by recording pushrod displacement and air brake service line pressure as a function to time. The test hardware utilizes easy to fabricate “clip on” transducers to measure pushrod stroke length. Data acquisition is via LABVIEW‚. All transducers are easy to temporarily affix to any tractor- trailer and require no alteration to the vehicle. A complete system check takes less time than manually measuring pushrod stroke as required under FMCSA. This system with one treadle application and release gives digital timing and displacement history of all brakes. Useful information includes: application and release profiles (pushrod velocity), shoe compliance upon seating and crack pressure release points for both tractor and trailer relay valves.

The transporting of live cattle involves the use of Class 8 tractors and livestock semi-trailers for transportation from farms and feedlots to processing plants. This travel may include unimproved roads, local streets, two lane highways, as well as interstate highways. Typically, cattle are compartmentalized in a “double deck” fashion as it provides utility and comports with size and weight limits for commercial Class 8 vehicles. Concern has been expressed for the effect of cattle movement upon the dynamic performance of the loaded Class 8 tractor-livestock trailer assembly. Loading guidelines exist for cattle that attempt to prevent injury or debilitation during transit, and literature exists on the orientation and some kinematics of loaded cattle. Considerable literature exists on the effect of liquid slosh in tankers and swinging beef carcasses suspended from hooks in refrigerated van trailers on the dynamic response and roll stability of those vehicles.

The flexibility of flat bed trailers is shown to be an important consideration in determining the static roll threshold for a loaded Class 8 tractor trailer. The development of an easy to use static roll threshold model using Microsoft® Excel's nonlinear equation solution capability provides a tool that should be useful to the trailer designer, dock loading manager and the traffic safety manager responsible for the training of drivers. It can be seen for low stiffness flat bed trailers that the trailer torsional stiffness is a more important parameter than typical suspension or tire stiffness. Further, even for “stiff” flat bed trailers the use of the rigid body roll criteria (T/2h) or the 2-D “planar” model can produce significant error in many practical loading configurations.

Air flow through the passages of a Chrysler LH platform ventilated brake rotor is measured. Modifications to the production rotor's vent inlet geometry are prototyped and measured in addition to the production rotor. Vent passage air flow is compared to existing correlations. The inlet modifications show significantly improved vent air flow, over the production rotor. The result improvement in heat transfer and rotor cooling is reported. These benefits in performance should be attainable at very low increases in production cost.

An experimental study was performed in order to determine whether or not ABS equipped automobiles leave skidmark signatures during emergency braking. The purpose of the study was to determine the feasibility of using conventional accident reconstruction methods on ABS equipped cars. Vehicles were braked from 65 mph (105 kph) on both asphalt and brushed concrete surfaces. A 1988 BMW 325 ES, a 1989 Mazda 626, a 1989 Nissan Maxima, a 1989 Oldsmobile Touring Sedan and a 1989 Toyota Supra Turbo were used as test vehicles. A 1987 Dodge Lancer, without ABS, was tested as a control vehicle. Data taken included stopping distance, skid mark lengths and deceleration rate. Vehicle handling and skid mark visibility were also noted. The experimental program showed that ABS equipped automobiles produce no discernable skidmarks under emergency, dry pavement braking conditions.

Several accident reconstruction computer programs provide trajectory simulation information to determine the path of the vehicles from impact to rest. Many of these will even plot the information to the computer screen or printer. What all of these plotting programs seem to lack, however, is a way to include scene data such as the locations of trees, poles, and parked cars. It is possible to merge the superior scene drawing capabilities of commercial CAD/CAM packages with the results of trajectory simulations to produce a time sequence drawing or a real time simulation. This combination of tools results in output that fully depicts the reconstruction in every detail and makes an impressive display in the courtroom should litigation be involved. Techniques are discussed that are general to all brands of reconstruction and CAD/CAM software. Specific examples are given using CRASH3-PC, from the U.S. Department of Transportation and AutoCAD, from Autodesk, Inc.