Question

It is proposed to widen and strengthen an existing 2-lane NH section as a divided highway. The existing traffic in one direction is 2500 Commercial Vehicles (CV) per day. The construction will take 1 year. The design (CBR) of soil subgrade is found to be 5%. Given, traffic growth rate for CV = 8%, vehicle damage factor = 3.5 (standard axles per CV) design life = 10 yr and traffic distribution factor = 0.75. The cumulative standard axles (msa) computed are

• A. 37
• B. 35
• C. 65
• D. 70

Answer 1

The correct option is A 37

2 lane NH is divided highway
As the highway is divided we will consider traffic in one direction only

Number of commercial vehicle per day
$=2500\times \text{traffic distribution factor}$
$=2500\times 0.75=1875$

Traffic growth rate,
$r=8\%$

Construction will take one year so number of commercial vehicle per day at the end of construction

$A=1875(1+0.08{)}^1=2025$

Cumulative standard axles,
$N_s=\frac{365A[{(1+r)}^n-1]}{r}\times F$
$=\frac{365\times 2025\left[\right(1+0.08{)}^{10}-1]}{0.08}\times 3.5$
$=37.47\times {10}^6$
$=37.47msa$