7.6 Preview Sight Distance and Grade Perception at Vertical Curves Preview sight distance measures the motorist sight distance required under the assumption they base their behaviors on a preview of the road surface and other cues that lie downstream. The concept...
7.4 Design Considerations for Turnouts and Grades Truck escape ramps provide a space for out-of-control trucks to slow down and stop away from through traffic. Table 7.2 lists design guidelines for geometrics and signing. Table 7.2 Guidelines for Geometrics and...
7.2 Design Considerations for Turnouts and Grades Turnouts are widened, unobstructed shoulder areas where slow-moving vehicles can turn out of the through lane so quicker vehicles may pass. They are particularly valuable on two-lane highways in mountainous areas....
5.12 Influence of Speed on Sight Distance When operating speeds are much faster than design speed, increasing sight distance to account for higher vehicle speeds can be a good option. Table 5.8 summarizes how different aspects of a road’s design influences operating...
5.10 Determining Passing Sight Distance Passing sight distance is the length of roadway downstream a motorist must be able to see to safely complete a passing maneuver. Safe completion means the motorist does not cut off the vehicles they are passing before they meet...
5.8 Determining When to Use Decision Sight Distance Decision sight distance is longer than stopping sight distance. Its use is appropriate in road environments where motorists (a) make complex or instantaneous decisions, (b) have difficulty perceiving information, or...
