31
Table 4.5: Total VDF for Each Type of Heavy Vehicle Used in This Study
As seen in Table 4.5, the total VDF of Demak – Trengguli direction is higher than the
opposite direction. The deviation of VDF is mainly contributed by VDF of classes 6B, 7C1 and 7C3.
4.3 Calculation of Traffic Load
The calculation of traffic load W
18
in equivalent standard axle load ESAL should be based on the actual VDF and ADT. AASHTO Design Guide gives the following formula to
determine the traffic load for design lane W
18
.
365 x
G x
x
Ri 18
i i
i
E ADT
W 2.2a
W
18
= D
D
x D
L
x
18
W
2.3
where: ADT
i
= average daily traffic for axle load i; E
i
= axle load equivalency factor or vehicle damage factor VDF for axle load i; G
Ri
= annual growth rate depends on traffic growth rate, g, in percent; and service life, n, in year axle load i;
D
D
= directional distribution factor; D
L
= lane distribution factor;
18
W
= cumulative standard axle load for two directional 18-kip ESAL units predicted for a specific section of highway during the analysis period from the planning group.
Direction VDF for heavy vehicles
Class 6B 2 axle
Class 7A 3axle
Class 7C1 4 axle
Class 7C2 5 axle
Class 7C3 6 axle
Demak – Trengguli
10.91 5.36
22.01 13.5
24.3 Trengguli
– Demak 2.432
3.15 10.57
12.72 8.18
32
Road section Demak – Trengguli or Trengguli - Demak is a four-lane two- direction divided 42
D road, therefore, in this case, D
D
and D
L
equal to 1 and 0.8, respectively. The traffic load on Demak
– Trengguli or Trengguli – Demak road section was assumed to increase 6 per anuum and the road could serve traffic load for the next 10 years. Based on this assumption, the traffic
load W
18
on Demak – Trengguli and Trengguli – Demak in two conditions, i.e. standard as
designed and overloaded conditions, are depicted in the following table.
Table 4.6: Traffic load as designed and overloaded condition
Direction W
18
in million ESAL As Designed
Overloaded
Demak – Trengguli
19.542 100.850
Trengguli – Demak
20.715 40.380
Table 4.6 shows that there is no different on traffic load for both directions in standard condition, but in overloaded condition, traffic load of Demak -Trengguli direction is 2.5 higher than
opposite direction. This is because the significant deviation of the VDF in Demak-Trengguli direction see table 4.5, although the ADT of Demak-Trengguli was lower than the opposite
direction.
4.4 Reduction of Pavement Service Life
