Superelevation runoff and tangent runout layout for a highway curve
A 6 percent superelevation transition is laid out around a 1000 ft radius curve: runoff and runout lengths from the relative gradient, the five key stations, and edge-of-pavement elevations for the stakes.
Analyze· about 32 minutes by hand· 5 steps
Given
A two-lane highway curve to the right, R = 1000.00 ft, Δ = 30°00′00″, PI at station 76+80.00.
Travelled way 24.00 ft wide, two 12.00 ft lanes, rotated about the centerline.
Normal crown 2.0 percent each way from the centerline.
Design superelevation e = 6.0 percent.
Maximum relative gradient between the centerline profile and the pavement edge = 0.50 percent for this design speed.
Agency practice places two thirds of the superelevation runoff on the tangent ahead of the PC and one third on the curve.
Centerline profile: a constant +1.20 percent grade, elevation 612.40 ft at station 74+00.00.
All distances in US survey feet; elevations to 0.01 ft.
Required
Stations of the PC and the PT.
The superelevation runoff length and the tangent runout length.
The five key transition stations at the approach end, with the cross slope at each.
Centerline and edge-of-pavement elevations at those stations.
Work it through yourself before reading on - the solution below shows every step, so there is no way to skim it without giving the answer away.
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