A six-lane divided highway is to be designed to replace an existing highway. The present AADT (both directions) of 6000 vehicles is expected to grow at 5% per annum. Assume SN = 4 and pt = 2.5. The percent of traffic on the design lane is 45%. Determine the design ESAL if the design life is 20 years and the vehicle mix is:
Passenger cars (1000 lb/axle) = 60%
2-axle single-unit trucks (5000 lb/axle) = 30%
3-axle single-unit trucks (7000 lb/axle) = 10%
What will be an ideal response?
Use Equation 19.2 to determine ESALs:
ESALi = (fd)(Gjt)(AADTi)(365)(Ni)(FEi)
The design lane use factor, fd, is given as 0.45
From Table 19.6, the growth factor, Gjt is 33.06 for a growth rate of 5% and
design life of 20 yr
From Table 19.5a, by interpolation, the load equivalency factors are:
2 axle SU truck = 0.008
3 axle SU truck = 0.027
ESAL2-axle SU truck= (0.45)(33.06)(6000)(0.3)(365)(2)(0.008)
ESAL2-axle SU truck = 1.56 × 105
ESAL3-axle SU truck = (0.45)(33.06)(6000)(0.1)(365)(3)(0.027)
ESAL3-axle SU truck = 2.64 × 105
Note that the contribution of passenger car traffic to ESALs is negligible and
therefore not considered in the calculations.
Total ESAL = 4.00 × 105
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