Effect of Grades on Superelevation. On long and fairly steep grades, drivers tend to
travel somewhat slower in the upgrade direction and somewhat faster in the downgrade
direction than on level roadways. In the case of divided highways, where each pavement
can be superelevated independently, or on one-way roadways such as ramps, this tendency
should be recognized to see whether some adjustment in the superelevation rate
would be desirable and/or feasible. On grades of 4 percent or greater with a length of
1000 ft (305 m) or more and a superelevation rate of 0.06 or more, the designer may
adjust the superelevation rate by assuming a design speed 5 mi/h (8 km/h) less in the
upgrade direction and 5 mi/h (8 km/h) greater in the downgrade direction, provided
that the assumed design speed is not less than the legal speed. On two-lane, two-way
roadways and on other multilane undivided highways, such adjustments are less feasible,
and should be disregarded.
Effect of Grades on Superelevation. On long and fairly steep grades, drivers tend totravel somewhat slower in the upgrade direction and somewhat faster in the downgradedirection than on level roadways. In the case of divided highways, where each pavementcan be superelevated independently, or on one-way roadways such as ramps, this tendencyshould be recognized to see whether some adjustment in the superelevation ratewould be desirable and/or feasible. On grades of 4 percent or greater with a length of1000 ft (305 m) or more and a superelevation rate of 0.06 or more, the designer mayadjust the superelevation rate by assuming a design speed 5 mi/h (8 km/h) less in theupgrade direction and 5 mi/h (8 km/h) greater in the downgrade direction, providedthat the assumed design speed is not less than the legal speed. On two-lane, two-wayroadways and on other multilane undivided highways, such adjustments are less feasible,and should be disregarded.
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