10.4 Factors Affecting Acceptable Gap Distances Many factors influence acceptable gap distance. When making assumptions about acceptable gap distance, it is important for designers to keep in mind issues summarized in Table 10.2 Table 10.2 Factors that Influence...
9.2 Perceptual and Physical Elements to Support Rural-Urban Transitions When motorists driving at a high speed enter an area with lower speed limits, they tend to underestimate their speed and not adjust it downward enough. The design of transition zones needs to...
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...
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...
5.8 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...
5.6 Determining Intersection Sight Distance Drivers must have a clear view of an entire intersection so they can see traffic control devices and see far enough upstream or downstream along an intersecting road to identify acceptable gaps in cross traffic before...
