Question

What is the minimum length of taper beyond the physical nose (with offset of 20 ft) of an off- ramp which no rigid obstacle should be placed? Assume the design speed of highway is 60 mph.

a) 800’ b) 700’ c)500’ d) 600’

Answer 1

For freeways, expressways, and other roadways having a speed of 45 mph or greater, the minimum length for merging tapers should be computed by a formula

L = W x S.

  where,

L is the taper length in feet,

W is the lateral shift of traffic due to the partially or fully closed lane (in feet)

   S = Posted speed, off-peak 85th percentile speed prior to work starting, or the anticipated operating speed in mph.

L = 20*60 = 1200 ft

Shifting Taper (L/2) - When there is a lateral shift in the path of the lanes, but there is no reduction in the number of travel lanes.

Taper length = L/2 = 1200/2 = 600 ft