to two-lane roadways only. Among the assumptions that affect the required distance calculations
are (1) the passing vehicle averages 10 mi/h (1.61 km/h) faster than the vehicle
being passed, (2) the vehicle being passed travels at a constant speed and this speed is the
average running speed (which is less than the design speed), and (3) the oncoming vehicle
is traveling at the same speed as the passing vehicle. Table 2.3B contains K values for
designing crest vertical curves to provide passing sight distance. These values assume that
the height of the driver’s eye is 3.5 ft (1.07 m) for both the passing and the oncoming vehicle.
The equations at the bottom of the table provide mathematical solutions for sight distance
on the crest curves.