A tunnel at level grade has a design speed of 120 km/h and curves of 1000 m radius. The tunnel has one lane in each direction. Each lane is 4 m wide and the sidewalk is 2 m wide. (3 decimal places) a. Determine an appropriate superelevation rate for the circular curve. b. Check if the available sight distance exceeds the SSD. c. If the answer is no in part b, determine what the posted speed limit should be to ensure safe stopping.