9.4.2 Design Speed

Similar to facilities with design speeds of 80-mph or less, ramps on these facilities must have a relationship between the ramp design speed and the mainlane design speed. All ramps and direct connectors must be designed to enable vehicles to leave and enter the travel way of the highway at 85 percent (desirable) to 70 percent (usual minimum) of the highway design speed, rounded up to the nearest 5- mph increment, and limiting the speed differential to 10-mph on the upper range and 20-mph for the mid-range.
Every effort should be made to meet the upper range ramp/connector design speed.
Table 9-11
shows the values for ramp/connector design speeds.
Table 9-11: Guide Values for Ramp/Connector Design Speed as Related to Highway Design Speed
1
Ramp/Connector Design Speed
2
 (mph)
Highway Design Speed (mph)
85
90
95
100
Upper Range (85%)
75
80
85
90
Mid-Range (70%)
65
70
75
80
Lower Range (50%)
55
60
65
70
Notes:
  1. Values determined by the percentage of the highway design speed or the max difference between highway and ramp design speed (10 mph for upper, 20 mph for mid, 30 mph for lower), whichever is higher.
  2. For corresponding minimum radius for applicable ramp speed and superelevation rate e-max, see Table 4-6, Table 4-7, Table 9-5 and Table 9-6.