Evaluation of traffic control procedures for construction work zones containing pavement edge drop-offs
Date
1998
Authors
Root, Vicki Sue
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Kannel, Edward J.
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Abstract
Pavement edge drop-offs commonly occur in construction work zones as the result of pavement overlays, pavement replacement, or shoulder replacement. The depth of the drop-offs can range from one inch when a flexible pavement overlay is applied up to two feet when a full-depth rigid pavement or shoulder is being replaced. The degrees of safety associated with pavement edge drop-offs depend on several factors including: (1) the height of the edge drop-off, (2) the shape of the pavement edge, (3) and the speed of the vehicles. This research attempted to find out how these, and other factors of a construction work zone, affect the way a pavement edge drop-off is mitigated. Considerable variation from one state to another in the procedures used for handling edge differentials in construction zones.
Some states base their traffic control plans on only one factor, the depth of the edge drop-off. Other states use additional factors such as the expected duration of the project, the posted speed limit, the average annual daily traffic (AADT), and the lateral distance between the travel lane and the edge drop-off. All of the states surveyed indicated that they treat the drop-off before it exceeds a depth of three inches. The depth of drop-off requiring the use of portable concrete barriers varies anywhere from two inches to two feet, depending on the individual state policy. Accidents that are related to construction zone pavement edge drop-offs appear to be very sparse in the State of Iowa. No major problems were detected in the current traffic control plans used by the Iowa DOT for construction zones that contain pavement edge differentials.
Motorists seemed to drive through the construction zones with out much difficulty and without significantly reducing their travel speeds. A specific strategy on how to select the safest and most cost-effective traffic control plan to be used in construction work zones which contain pavement edge drop-offs could not be developed. Even though the benefit-cost analysis was inconclusive, this research could be used asthe base for future studies.
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