FLH PDDM Chapter 9 - Eastern Federal Lands Highway Division

9.4.A. Geometric Design. (continued)Table 9-3Example Listing of a Determination of Superelevation RatesTangent / Curve Safe Speed Adjusted "e" for Adj. Run OffLeft/Right emax8% Design Speed Design Speed Length(meters)/(radius) (km/h) (km/h) (percent) (meters)190 m Tangent100 100600 m Radius 120 100 6.9 56Curve Right98 m Tangent300 m Radius 90 80 7.6 55Curve Left84 m Tangent200 m Radius 75 70 7.9 52Curve Right73 m Tangent150 m Radius 67 60 7.8 47Curve Left80 m Tangent300 m Radius 90 80 7.6 55Curve Right93 m Tangent900 m Radius 145 100 5.2 56Curve Left97 m TangentNOTE: Enter tangent length in meters and the curve radii in the first column. From Figure III-10 through Figure III-14,Design SuperelevationRates in the 1994 “Green Book”, determine the maximum safe speed at a superelevation rate of 8% for each curve and record in column 2. Nowadjust each curves design speed for the maximum 20 km/h differential between curves. Start with the sharpest curve (the 150 and 200 m radiuscurves) and continue by increasing the design speeds accordingly on the adjacent curves. Leaving a long tangent, the process is reversed. Startwith an estimated driving speed for the tangent and reduce the speed by 20 km/h for the adjacent curve. Record the runoff or spiral length actuallyused in the last column. These are helpful for future checking. Include the analysis in the design study.9 - 23