chapter 3 rigid pavement - DOT On-Line Publications - Department ...

The type of trdck monitored in this study was semi-nac;or :rai;ers. p~s~e~.~o:
vehicles and smaller single unit treks have considerably less impacr on edge S;ressej
and were not induded in the sample. AS with the Georgia study, no data was taken
on days with a strong cross-wind. Also, the study section was on rural interstate anti
the terrain was fiat;with no hotiontal curvature within 2000 ft (610 m) of the test
sections, in order to further reduce the effect of external factors. Film from 8mm
movie cameras was reviewed by the University of Iilinois staff to obtain the data.
A summary of the lateral encroachments on the edge of the pavement is given
in table 4.“’ A comparison of the average lateral placement of the truck tires in the
control section with the extended PCC pavement slab section leads to the concicsion
that trucks will not significantly move outward in the designated traffic lane. Ct’heel
path locations show that trucks tend to drive approximately 2 in (51 mm) closer to
the edge line stripe on an extended PCC pavement slab. This would tend to ir.dica:e
that with adeauate slab widt.,. b the oavement striue location controls the lareral wkeei
path in which the trucks travel rather than the overall width of the gavemerrt itself.
The trucks stayed an average of 20 to 22 in (508 to 359 mm) away from the
edge Iane stripe, whether on a 12-ft (3.7 m) PCC slab or an extended PCC slab
marked with a 12-ft (3.7 m) driving lane. At first, the 20 to 22 in (508 to 339 mm)
distance may seem adequate, but after evaluating the data it can be seen that
approximately 30 percent of the semi-tractor trailers travel 18 in (457 mm) or less
Table 4. Values of sample size, lateral distance D (fig&es 2 and 3”‘),
standard deviation, and percent shoulder encroachments for
the lateral distribution of truck wheel paths (reference 4).
Distance
Percent Shoulder
Sunpk From Edge Erraoachmencs
size ‘D, in lane Standard (Beyond Lane
Wehide) (Fig. t&3)” smpe, ul Dev.. VI Smpe)
Control Section 536 22.0 22.0 9.0 0.7
18-in Extended Section 691 38.1 20.1 9.1 1.7
to-in Extended Section 613 40.5 20.3 9.1 0.7
3.8.12