9.2.11 Vertical Curves

Vertical curves create a gradual transition between different grades which is essential for the safe and efficient operation of a roadway. The lengths of both crest and sag vertical curves are controlled by the available sight distance.
Vertical curves are required for all grade breaks on mobility corridors.
Minimum K-values are calculated using the same equations as in
Chapter 4 , Section 4.8
. Design Ks for both crest and sag vertical curves are shown in
Table 9-8
.
Table 9-8: Minimum Design K Values for Crest and Sag Vertical Curves
Design Speed
(mph)
Stopping Sight Distance
(ft)
Crest Vertical Curves
(K)
Sag Vertical Curves
(K)
85
1,010
473
260
90
1,110
571
288
95
1,220
690
319
100
1,330
820
350
The length of a sag vertical curve that satisfies the driver comfort criteria is 60 percent of the sag vertical curve length required by the sight distance control. Driver comfort control should be reserved for special use and where continuous lighting systems are in place.