TABLE OF CONTENTS An interchange ramp is a roadway that connects two legs of an interchange. Ramp cross-section elements are discussed in Art. 2.3, Cross-Section Design. Elements contributing to horizontal and vertical alignments are designed similar to any roadway once the ramp design speed has been determined.
To design horizontal and vertical alignment features, a design speed must be determined for each ramp. Since the driver expects a speed adjustment on a ramp, the design speed may vary within the ramp limits. Table 2.26 includes three ranges of ramp design speeds that vary with the design speed of the mainline roadway. The ramp design speed range is determined by judgment based on several conditions:
| Mainline design speed, mi/h | 30 | 35 | 40 | 45 | 50 | 55 | 60 | 65 | 70 |
|---|---|---|---|---|---|---|---|---|---|
| Ramp design speed, upper range, mi/h | 25 | 30 | 35 | 40 | 45 | 45 | 50 | 55 | 60 |
| Ramp design speed, middle range, mi/h | 20 | 25 | 30 | 30 | 35 | 35 | 40 | 45 | 50 |
| Ramp design speed, lower range, mi/h | 15 | 15 | 20 | 20 | 25 | 25 | 30 | 30 | 35 |
| Source: Location and Design Manual, Vol. 1, Roadway Design, Ohio Department of Transportation, with permission. |
The types of roadways at each end of the ramp and their design speeds
The length of the ramp
The terminal conditions at each end
The type of ramp (diamond, loop, or directional)
Diamond ramps normally have a high-speed condition at one end...
