A two-lane minor road intersects a two-lane major road at 90° forming a four-leg intersection with traffic on the minor road controlled by a yield sign. A building is located 110 ft from the centerline of the outside lane of the major road and 40 ft from the centerline of the nearest lane of the minor road. Determine the maximum speed that can be allowed on the minor road if the speed limit on the major road is 40 mi/hr. Grades are approximately level.

Question

What will be an ideal response?

Answer 1

Given:

a = 110 ft

b = 40 ft

Table 7.9 discusses the different cases when different speed limits are applied on

the minor road.

When vminor = 15 mph, db = 75 ft < a = 110 ft. Hence, there is no restriction on

the speed limit on the major road.

When vminor = 20 mph, db = 100 ft < a = 110 ft. Hence, there is no restriction on

the speed limit on the major road.

When vminor = 25 mph, db = 130 ft > a = 110 ft, and ? g t 6.5 sec. From Equation

7.7, the sight distance along the major road should be



At site, the maximum sight distance along the major road can be computed using

Equation 7.4 :



Hence, the maximum speed that can be allowed on the minor road is 20 mph.