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This paper provides an overview of the current state of knowledge on medium and heavy truck safety and reviews the results of truck safety research sponsored by the Motor Vehicle Manufacturers Association. A number of issues have been raised about the accident experience of trucks, and the injuries and fatalities sustained by occupants. The diverse viewpoints and perceptions which exist on the reasons for these accidents and what countermeasures should be taken are reviewed. The evolutionary nature of truck accident research is presented, pointing out that sufficient detailed accident and injury data are lacking. Corresponding information on truck configuration, size, weight and exposure data remain inadequate. The role of the vehicle, driver, and highway environment in accident causation must be known and methods to achieve this goal are examined. Despite these limitations, there is progress in understanding the causes of truck accidents.

From various sources of information it is clear that truck noise is a definite public nuisance. Early noise control efforts were very productive in that many heavy duty trucks did not have mufflers, and the addition of this device made clear improvements. Further improvement requires treatment of many sources significant to the overall level. It is felt that today's “tight but attainable” 88 dBA for heavy trucks can reduce to 86 dBA by 1975 and 8k dBA by 1978 with a lot of hard work. There is promise for meaningful noise regulation in the “real world” as indicated by “calibratability” of non-standard sites.

The impact of farm and industrial tractors on the total national emissions picture is difficult to assess because the great diversity of uses for these machines results in a wide variation in duty cycles and degrees of utilization. Also, there is a general lack of detailed information on population and population distribution. This paper compares possible farm tractor duty cycle models and concludes that the widely used 13-mode federal heavy-duty diesel engine emissions test cycle can be used to estimate wheel tractor emissions. Estimates then are given for the amount of pollution released by wheeled farm and industrial tractors in 1972, based on the 13-mode cycle and population estimates derived from U.S. Dept. of Commerce, U.S. Dept. of Agriculture, and Farm and Industrial Equipment Institute data. Calculations show wheeled tractor emissions contribute 3.2% or less of the national total, depending upon the pollutant species.

The Vehicle Maintenance Reporting Standards of the American Trucking Associations can be used by manufacturers to improve heavy-duty vehicles. After verifying the accuracy and significance of the data the manufacturing, engineering, technical service and marketing departments can all use the information to improve vehicles and provide better service to the user.

IN the first part of this paper, Mr. Halgren discusses modified 4-square testing of gears in relation to service performance, field tests, and other accelerated laboratory test methods. It contains a short description and photographs of nine different designs of modified 4-square gear testing machines now in use. Description of machines includes comments on mounting rigidity, mass-elastic system, load application, measurement and control, shut-off devices, and lubrication. Mr. Wulpi discusses single-tooth fatigue testing which is used to measure the bending strength of gear teeth. One tooth at a time is tested in the manner of a cantilever beam. By successive testing, many teeth of the same gear may be tested, and endurance limits obtained if desired. Results of these tests show that it is possible to determine clearly the effect of various metallurgical factors, such as material, heat-treatment, or surface-finishing treatment upon the bending-fatigue strength of gear teeth.

A study to define accurately and discover new parameters of productivity for the contractor has resulted in a new design concept in off-highway trucks. This new concept has been first applied in the International Model 180 Payhauler, a rear dump vehicle of 45 ton rated capacity. The function and form criteria are discussed by components and systems in terms of the complete vehicle and on the job applications.

Five geometrically similar bulldozer blades, ranging in width 6.45-77.2 in., were tested in four different soil types. Tests were run at low speed and a constant cutting depth equal to 20% of blade height. Horizontal and vertical soil forces, soil force moments, and travel distances were measured. An analysis of the test data is presented and a method of predicting the draft force of larger blades from tests on smaller scale models is proposed. Test equipment, instrumentation, and test technique are described.

Prior to World War II, most heavy duty highway trucks and tractors were built as Conventionals, i. e., with the cab mounted behind the engine. In the late 1940's cab-over-engine types gained acceptance and in the 1950's the tilt cab COE was developed in its present form including sleeper cabs. The new concept is to combine the best features of conventionals and tilt cab COEs to develop a superior non-sleeper tractor that makes no compromises for sleeper cab types.

THE NEW DIESEL ENGINES developed recently by International Harvester are adaptations of existing carbureted truck engines. The manufacturing economies possible by employing existing machine tools were the governing consideration in their design. This paper discusses solutions found to the many problems presented by this approach to engine design: crankshaft, crankcase, connecting rods, pistons, lubricating system, and the like. Extensive interchangeability of parts was a result of the design concept. The engines have been successfully adapted to farm tractors, crawler tractors, stationary motors, and various automotive applications.*

Splash and spray conditions created by tractor-trailer combinations operating on the Federal highway system have been studied and tested for many years with mixed results. Past events are reviewed briefly in this paper. In additional testing during 1983, using new state-of- the-art splash/spray suppressant devices, some encouragement was provided that these devices could work. The 1984 Motor Vehicle Manufacturers Association (MVMA) test program was designed to develop practicable and reliable test procedures to measure effectiveness of splash and spray reduction methods applied to tractor-trailer combination vehicles. Over 40 different combinations of splash/spray suppression devices on five different tractors and three van trailer types were tested. The spray-cloud densities for some 400 test runs were measured by laser transmissometers and also recorded by still photography, motion pictures, and videotape. On-site observers made subjective ratings of spray density.