Recent Roadway Geometric Design Research for Improved Safety and Operations (2012) / Chapter Skim
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Pages 65-72
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From page 65... ...
. • Observation of driving behavior revealed that the strong- est indicator of operating speed was posted speed limit.
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From page 66... ...
Designers should avoid intersections with state highways and high-volume county roads within passing lanes, consider terrain and right-of-way in determining alignment and placement of passing lanes, avoid the termination of passing lanes on uphill grades, and discourage passing lane lengths longer than 4 mi (Brewer et al.
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From page 67... ...
. rumble Strips • Crashes at approximately 210 mi of undivided rural two-lane roads treated with centerline rumble strips were reduced by 14% and injury crashes were reduced by an estimated 15%.
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From page 68... ...
– Provide appropriate sight distance and visibility for driver recognition of the intersection and conflicting users." • Maximum entering design speeds are based on a theoretical fastest path of 20 to 25 mph for single-lane roundabouts and 25 to 30 mph for multilane roundabouts (Rodegerdts et al.
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From page 69... ...
All nonmotorized users who are likely to use the sidewalk regularly, including bicyclists in situations where roundabouts are designed to provide bicycle access to sidewalks, should be considered in the design of the sidewalk width. Recommended designs for single-lane roundabouts encourage bicycle users to merge into the general travel lanes and navigate the roundabout as a vehicle, explaining that the typical vehicle operating speed within the circulatory roadway is in the range of 15 to 25 mph, which is similar to that of a bicycle (Rodegerdts et al.
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From page 70... ...
– Median widths of more than 50 ft generally should be avoided at suburban, unsignalized intersections. • Keep median opening lengths at rural divided highway intersections generally to the minimum possible.
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From page 71... ...
DLT lanes typically cross the opposing through traffic at locations that are approximately 400 to 500 ft upstream of the signalcontrolled ramp terminals. Minimum median widths are preferred for this design (Hughes et al.
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From page 72... ...
More research is needed to quantify how driver yielding behavior is related to travel speed and different roadway characteristics, such as lane widths, pavement conditions, horizontal and vertical shifts, sight distances, lateral clearance, and other factors. This research should be used to create improved guidelines for roadway design and traffic calming practice.
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