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Insufficient PSD can degrade operations and increase risk-taking by drivers. The effects of insufficient PSD may not be evident or significant except where traffic volumes approach the capacity of the two-lane highway, or where the volume of heavy- or slow-moving vehicles is unusually great.
Insufficient PSD can degrade operations and increase risk-taking by drivers. The effects of insufficient PSD may not be evident or significant except where traffic volumes approach the capacity of the two-lane highway, or where the volume of heavy- or slow-moving vehicles is unusually great. Where operational or other evidence suggests lack of PSD is a problem, there are a number of measures designers can employ. These include construction of passing lanes, truck auxiliary lanes on long upgrades, or intermittent turn-outs for use by slower vehicles.
From A Guide for Achieving Flexibility in Highway Design, 2004, by the American Association of State Highway and Transportation Officials, Washington, D.C. Used by permission. AASHTO publications may be purchased from that organization's bookstore at 1-800-231-3475 or online at http://bookstore.transportation.org.
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