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Publication Number: FHWA-RD-00-055
Date: January 2000
What do you get when you mix a city of more than a half million people with 227 bridges and tunnels and a thriving economy? Traffic--and lots of it. The people who live, work, visit, or do business in Washington, DC, rely heavily on the District's roadway system. Although many components of the roadway infrastructure--which includes a bridge built in 1836--are in need of rehabilitation, the incessant travel demand makes it difficult to close a bridge to conduct a conventional rehabilitation project.
Throughout the United States, contractors and inspectors must contend with less-than-favorable weather conditions for road construction and rehabilitation. If an asphalt mix cools too rapidly, the mix will become stiff, making it difficult to compact to proper density. And a pavement that is not properly compacted will not hold up well to traffic loads.
A new Tech Brief available from the Federal Highway Administration (FHWA) describes some of the results of the most extensive pavement maintenance experiment ever conducted--the Strategic Highway Research Program (SHRP) H-106 project. Begun under SHRP and then continued by FHWA's long-term pavement performance (LTPP) program, the project's focus included better understanding the performance and cost-effectiveness of various cold-mix materials and procedures for repairing potholes in asphalt concrete pavements. Starting in 1991, more than 1,250 cold-mix pothole patches were placed at 8 test sites across the United States and Canada. Four different patching techniques-throw and roll, edge seal, semipermanent, and spray injection-were used at the test sites.
To learn how climate and cumulative traffic loading affect pavements of different compositions and layer thicknesses, State highway agencies across the country constructed specific pavement study (SPS) test sections during the past decade as part of the long-term pavement performance (LTPP) program. Eight of the 23 States with SPS-1 (flexible pavement) and SPS-2 (rigid pavement) test sections gathered in Columbus, Ohio, in November to exchange information on how the pavements are performing to date and to discuss plans for using the data collected.
Work zones on U.S. highways have become increasingly dangerous places for both workers and travelers, with the death rate approaching two per day. With more than 70,000 work zones in place across America on a given day, highway agencies are realizing that it is not enough to focus on improving the devices used in the work zone areas, but that they must also reach out to the public in order to change the behavior of drivers so that crashes can be prevented.
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