An existing intersection consists of a turning movement of 75 degrees, and the radius of the edge of pavement is 60 ft. The turning radius has no entry taper. What is the largest design vehicle that is accommodated at the intersection? What improvements would you recommend be made if this movement is to accommodate a WB-67 design vehicle?

Question

What will be an ideal response?

Answer 1

Table 7.2 shows the minimum edge of pavement design for turns at
intersections for simple curves and simple curves with tapers. It can be observed
that for an angle of turn of 75º and simple curve radius of 60 ft, the largest design
vehicle that can be accommodated at the intersection is a SU-30. Table 7.2 also
indicates that it is not feasible to have simple curves for large trucks when the
angle of turn is 75 degrees or greater. One option to accommodate a WB-67
design vehicle at this intersection is to add a 20:1 taper, with offset of 4.5 ft, and
the simple curve radius should be increased to at least 145 ft.
Table 7.3 shows the minimum edge of pavement design for turns at
intersections for symmetric and asymmetric 3-centered compound curves.
Another option to accommodate the WB-67 design vehicle is to change the simple
curve to a 3-centered compound curve, which will require curve radii of 420-75-
420 ft with 10ft offset for symmetric curves, or 200-80-600 ft with 1.0 and 10.0
offsets for asymmetric curves.