## Question

Problem 1

A rural collector highway located in a mountainous terrain is designed to carry a design volume of 800 vehicles per day (vpd). Determine the following:

a) Recommended design speed

Referring to Table 15.1 for mountainous terrain the minimum design speed is 30mi/h

b) Recommended lane width; Lane width = 12 ft,

c) Recommended shoulder width; usable shoulder width = 10 ft

d) Recommended grade From Table 15.3; maximum desirable grade = 10%

Problem 2

An urban freeway located in rolling terrain is designed to carry a design volume of 800 vehicles per day (vpd). Determine the following:

a) Recommended design speed

b) Recommended lane width

c) Recommended shoulder width

d) Recommended grade

(a) From Table 15.2, for urban freeway

minimum design speed = 50 mi/h

Problem 3

A rural collector is to be constructed in an area of rolling terrain where the ADT is 650 vehicles per day. For this situation, determine the following design values:

a) Recommended design speed

b) Recommended lane width

c) Recommended shoulder width

d) Recommended grade

Problem 4

A horizontal curve is designed for a two-lane road in mountainous terrain. The following data are known.

- Intersection angle: 40 degrees

- Tangent length: 436.76 feet

- Station of PI: 2700 + 10.65

- fs = 0.12

- e = 0.08

Determine the following:

a) Design speed

b) Station of the PC

c) Station of the PT

(a) From the given horizontal curve data, the radius can be calculated, from which

design speed for the curve can be derived.

The radius can be found by rearranging Equation 15.22,

R = T / (tan Δ/2) = 436.76 / tan (40Åã/2) = 436.76 / 0.3640 = 1200 ft

The design speed can then be found:

R = u2 / [15(e + fs)]

(1200) = u2 / [ 15 (0.08+0.12) ]

u2 = 3600

u = 60 mi/h

(b) Station of the PC can be found by subtracting the tangent length from the

station of the PI.

PC = (2700+10.65) – (4+36.76) = 2695+73.89

(c) The length of the curve can be found using Equation 15.26,

L = πRΔ/180 = (3.1415926)(1200)(40)/180 = 837.76 ft

Station of the PT can be found by adding the length of the curve to the

station of the PC.

PT = (2695+73.89) + (8+37.76) = 2704+11.65

(d) Deflection angle and chord length to the first full station

To find the deflection angle to the first full station, use Equation 15.27,

δ1/2 = 180 l1 / 2πR = (180)(100–73.89)/(2)(3.1415926)(1200) = 0.6233°

The chord to the first full station can be found using Equation 15.28,

C1 = 2R sin (δ1/2) = (2)(1200) sin (1.24666/2) = 26.11 ft

Problem 5

A simple circular curve exists with a degree of curve D = 12° and e = 0.08

A structure is proposed on land on the inside of curve. Assume the road is on level grade. Determine the following:

a) The radius of the curve (to the nearest foot)

b) The current maximum safe speed of the curve

c) The minimum distance (to the nearest foot) allowable between the proposed structure and the centerline of the curve such that the current maximum safe speed of the curve would not need to be reduced.

## Solution Preview

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Problem 1a) For a rural collector highway in a mountainous terrain, recommended design speed is 30 mi/h ( as per table 15.1 titled Minimum Design Speeds for Rural collector Roads).

b) Recommended lane width is 12 ft.

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