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Service roads, or frontage roads, as they are sometimes called, are used to enhance capacity on the mainline, control access, serve adjacent properties, or maintain traffic circulation. They permit development of adjacent properties while preserving the through character of the mainline roadway. Service roads may be either one-way or two-way, depending on where they are […]

Figure 2.47 shows recommended designs for multilane exit ramps and diverging roadways. A diverging roadway is defined as a single roadway that branches or forks into two separate roadways without the use of a speed change lane. Class I and II diverging roadways should be used when either or both the diverging roadways are mainline […]

When two roadways converge or diverge, the less significant roadway should exit or enter on the right. Left-hand exits or entrances are contrary to driver expectancy and should be avoided wherever possible. 2.7.1 Multilane Entrance Ramps and Converging Roadways Figure 2.46 shows recommended designs to be used for multilane entrance ramps and converging roadways. Converging […]

Collector-distributor (C-D) roads are used to minimize weaving problems and reduce the number of conflict points (merging and diverging) on the mainline. C-D roads may be used within a single interchange, through two adjacent interchanges, or continuously through several interchanges. 2.6.1 Design of C-D Roads When a C-D road is provided between interchanges, a minimum […]

Mainline crest vertical curves in the vicinity of ramp terminals should be designed using stopping sight distance values 25 percent higher than the design speed value from Table 2.18. Where a crest vertical curve occurs on an exit ramp at or near the nose, the crest vertical curve should be designed using the “upper-range” design […]

Superelevation at ramp terminals should be developed using the following guidelines. The rate of superelevation at the entrance and exit nose should be selected on the basis of the design speed of the ramp at the nose. All transverse changes or breaks in superelevation should be made at joint lines in concrete pavement. In the […]

A ramp terminal is the portion of a ramp adjacent to the through lane on the mainline. It includes both the taper and the speed-change lane. Ohio has recently revised its ter­minal criteria and uses two basic terminal classifications: High-speed terminals are intended for use on all facilities with a design speed of 50 mi/h […]

An interchange ramp is a roadway that connects two legs of an interchange. Ramp cross­section 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. 2.5.1 Ramp Design Speed To design horizontal and vertical alignment features, […]

An interchange is defined as a system of interconnecting roadways in conjunction with one or more grade separations that provides for the movement of traffic between two or more roadways or highways on different levels. Interchanges are utilized on freeways and expressways, where access control is important. They are used on other types of facilities […]

A two-way left turn lane may be considered a special type of “intersection” design, since its purpose is to provide a separate lane for traffic in both opposing lanes to slow down and turn out of the traffic stream in front of opposing traffic. Rather than concentrate the left turners at a single crossroad intersection, […]