42. (3 pts) What is the time savings from an intersection Assume standard defaul

Question

42. (3 pts) What is the time savings from an intersection Assume standard default walking speed of 3.5 ft/sec 43. (3 pts) What is the Structural Number of a pavement neckdown that reduces a 50 ft crossing by 20 percent? section with al, a2 ?? --0.44, 0.14, and 0.10 respectively if the depths are 5, 10 and 10 inches. 44. (3 pts) A road leading to a quarry is traveled by 50 trucks, with each truck making an avcrage of 20 trips per day. When fully loaded, cach truck consists of a front single axis transmitting a force of 10,000 lbf and a rear tandem axle transmitting a force of 20,000 lbf. The 18,000 lbf equivalent single axle load (ESAL) for the truck traffic in a given year is?

Explanation / Answer

Question 42:

Original Length of the crossing: 50 ft

Default walking speed: 3.5 ft/sec

Original time taken: 50/3.5 sec

Reduction is crossing is 20 percent.

New length of the crossing thus = 50 - 20/100 X 50 = 40 ft

New time taken to cross the crossing = 40/3.5 sec

reduction in time taken = 50/3.5 - 40/3.5 = 10/3.5 = 2.85 seconds.

Question 43:

Structural number (SN) of a pavement is given by, SN = a1D1M1 + a2D2M2 + a3D3M3 + ....

where, a is a layer coefficient that represents the relative strength of the material

D is layer thickness in inches

and M is a drainage coefficient

Subscript in the formula represents different layers.

M can be assumed to be 1.0 for each layer which indicates normal drainage characteristics.

Therefore, SN = 0.44 X 5 + 0.14 X 10 + 0.10 X 10 = 4.6

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