An intersection is being designed for two roads that intersect at approximately 60 degrees. For an SU-30 design vehicle, recommend a design for pavement edge for the right turn movement for the 60-degree turns and the 120-degree turns.

Question

What will be an ideal response?

Answer 1

1. 60º turn angle:
To accommodate the SU-30 design vehicle, a simple curve can be designed for a 60º angle of turn. According to Table 2, the simple curve does not require a taper and the radius should be at least 60 ft.
Table 3 shows that a compound curve is not indicated for the 60º turn angle if only a SU-30 design vehicle should be accommodated.
2. 120º turn angle:
A simple curve can also be designed to accommodate the SU-30 design vehicle at the intersection with a 120º turn angle, and Table 2 indicates that it requires a 10:1 taper, with 3.0 ft offset, and the radius of the curve should be at least 30 ft.
For the 120º turn angle, a symmetric 3-centered compound curve can also be designed. Table 3 shows that the radii should be 100-30-100 ft, with symmetric offset of 3.0 ft, to accommodate the SU-30 design vehicle. An asymmetric 3-centered compound curve is not indicated for this intersection.