Review of Truck Characteristics as Factors in Roadway Design (2003) / Chapter Skim
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Pages 39-60
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From page 39... ...
39 CHAPTER 5 TRUCK CHARACTERISTICS RELATED TO GEOMETRIC DESIGN This chapter reviews the available data on truck characteristics that should be considered in the development of highway design and operational criteria. The review of truck characteristics is based primarily on data from existing sources in published and unpublished literature.
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From page 40... ...
this phenomenon is small for bicycles and automobiles and is usually ignored. For trucks, however, it can be substantial and is an important factor in the design of intersections, ramps, and other highway elements.
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From page 41... ...
the following axle or hinge point relative to the center of its leader. These computed offtracking amounts are additive, except that the sign of the contribution from the center of the drive axles to the kingpin is reversed if the kingpin is moved forward (the usual case)
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From page 42... ...
findings, in reality there is a fair amount of dispersion in the actual paths used. DeCabooter and Solberg obtained actual offtracking paths for a number of intersections in Wisconsin (26)
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TRAILER SWINGOUT The front of a trailer is generally ahead of the front axles that support the trailer. Similarly, the rear of a trailer generally overhangs the rear axles.
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compliance with the IAN criterion if the rear axles are pushed back close to the rear of the trailer, but this design vehicle is substantially out of compliance if the rear axles are pulled forward to obtain a 12.5-m [41-ft] KCRT distance.
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From page 45... ...
value that typically occurs between 10 and 15 percent slip. The coefficient of braking friction then decreases as percent slip increases, reaching a level known as the coefficient of sliding friction at 100 percent slip.
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(5) where BD = braking distance (ft)
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Both References 32 and 33 indicate that the friction coefficients of truck tires decrease slightly with increasing axle load. Tire inflation pressure has very little effect on peak friction coefficient (fp)
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this is a very conservative choice. The best-performance drivers can operate at efficiencies approaching 100%.
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driver can see farther than a passenger car driver on the approach to vertical sight restrictions. The AASHTO Green Book specifies a value of 1,080 mm [3.5 ft]
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8.2-m [27-ft] trailers.
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its speed from 56 to 88 km/h [35 to 55 mph]
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or resisting its forward motion. This figure is for a very low performance truck, by today's standards, that is barely able to achieve 105 km/h [65 mph]
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to-power ratios, the database developed in that study was obtained and reanalyzed in the FHWA Truck Characteristics study (2,3)
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mid-1980s other than the results of a field study by Harwood et al.
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Aerodynamic Drag The aerodynamic drag force is estimated by the following relationship (43)
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SUSPENSION CHARACTERISTICS This section of the report reviews the characteristics of truck suspensions. The review is based primarily on a summary of suspension characteristics from the NHTSA factbook of truck characteristics (18)
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ization is a static quantity; dynamic inter-axle load transfers are discussed in the next section. Typically, most tandem axles are very good at distributing the load evenly between the axles.
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aft. This unintentional steering is created by the suspension and tire forces.
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a rollover; however, this is a very unstable situation and could ultimately lead to a rollover. Earlier research, largely based on modeling, indicated that an extreme rollover threshold as low as 0.24 was possible (50, 54)
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From page 60... ...
about the assumed medium density. No data on cargo density were available, however.
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