Page 100 - Lecture Notes DCC3113

The magnitude of maximum loading is commonly controlled by legal load limits. Traffic survey and
loadometer studies are often used to establish the relative magnitude and occurrence of the various
loading to which a pavement during its design life is a very difficult but obviously important task.
Most design procedures provide for an increase in traffic volume on the basis of experience by using
some estimate growth rate.

Single Axle Tandem Axle Tridem Axle

Figure 7-3: Traffic Loading

The standard axle load, Ls, is equivalent to 80kN or 8200kg or 18,000 pounds or 8.16 tonne. One
application of a load L, is equivalent in terms of damage to F applications of the standard load Ls where

Load equivalency factor, F = (L/Ls)
4

 Consider only commercial vehicles CV (BTM > 1.5 ton, 3 ton for RN31)

1.5 4 Lorry 9 tonnes
( ) Car 1.5 tonnes 9 4
8.16 ( )
= 0.00114 8.16
= 1.48

18 4
( ) 26 4
8.16 ( )
= 3.67 8.16
= 103.1
Bus 18 tonnes Trailer 26 tonnes

Figure 7-4: Calculation to define load equivalency factor for
different type of vehicles

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