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Urban Freeway Renewal
by David O. Cox Frequently, highway officials are faced with a situation like this: An old pavement on a heavily traveled route in the heart of an urban area has served its useful life - and more. Over the years as traffic loadings have doubled and then doubled again, the road has been patched, refurbished, and overlaid. All in all, highway engineers are very pleased with its performance, but this pavement has finally reached that inevitable point where rehabilitation just won't work any more. This pavement must be replaced! How can it be replaced in an efficient and cost-effective manner and with as little disruption as possible to the economy and to the travel patterns of the hundreds of thousands of people who depend on this route? Sound familiar? It should because as the Interstate Highway System begins to show its age, virtually every large city in the United States has routes with pavements that match this description. Many cities have used costly maintenance-intensive "fixes" that do not fully resolve the problem and that force their citizens to live a bit longer with substandard pavements. The 1997 issue of Highway Statistics presents the scope of this problem. In the United States, more than 34,000 kilometers of urban freeways are currently rated as being in need of replacement now or in the very near future. This is approximately 28 percent of the total length of urban freeways. Another 18,000 kilometers (15 percent) are predicted to reach that condition by the year 2005. The cost of "system preservation" in urban areas is already high and growing at a tremendous rate - from just over 42 percent of the total highway construction dollars spent in 1995 to nearly 50 percent in 1997. This means that together the states and the federal government spent almost $12 billion last year just to replace and repair some urban freeways, and still, the problem persists. Situations like this are complex. Within the overall context of the urban freeway pavement-reconstruction problem, many specific concerns and problems must be addressed. These include problems related to work-zone capacity, materials handling and supply, the safety of both motorists and highway workers, very complicated scheduling, and public relations. Furthermore, these projects can have dramatic economic impacts and can disrupt the plans and schedules of hundreds of thousands of people for the duration of the project. Clearly, finding cost-effective and customer-sensitive methods to reconstruct freeway pavements is an important national issue. Just as clearly, the solution to this problem will involve numerous highway disciplines and does not fit neatly into our current, more compartmentalized methods of research and study. Test Case - I-710 in Los Angeles In mid-1997, the Federal Highway Administration (FHWA), the Transportation Research Board (TRB), and the California Department of Transportation (Caltrans) formed a partnership to determine the best way to replace an urban pavement. The partners agreed to use Interstate 710 in Los Angeles as a test case. The partnership had two basic goals: (1) find a solution for I-710 and, in the process, identify the critical issues and provide a model for solving urban freeway problems, and (2) pioneer a new way of doing business within the highway community. Realizing that this mission cuts across traditional lines of expertise, the partners assembled four multidisciplinary teams with experts from throughout the country and representing the entire highway industry. The typical team was made up of a chief engineer from a state department of transportation (DOT), an FHWA division administrator, a state DOT project engineer, a specialist from the asphalt- or concrete-paving industry, a highway contractor, a pavement designer, a traffic engineer, a maintenance engineer, and a member of the academic community. Two of the teams were charged with producing an asphalt pavement design, and the other two a concrete pavement design. In addition, a team of public relations specialists and a team of life-cycle cost analysts are in the process of refining each of the recommended solutions. I-710 in Los Angeles is an excellent test case for this project. It is a 26-kilometer-long, eight-lane freeway with concrete pavement built in the 1950s. It currently carries more than 200,000 vehicles per day. As the primary access route to the city of Long Beach and to the port of Los Angeles, I-710 is both a heavily traveled truck route and a very important commuter route.
Although the workshop recommendations are still being analyzed and refined by Caltrans (and FHWA), all four teams designed a pavement with a structural life projected to exceed 40 years. It was acknowledged that both asphalt designs would need periodic surface restoration during the 40-year period and that perhaps the concrete designs would as well. In all cases, this was envisioned as a minimal project to correct surface deviations and restore ride quality and/or skid resistance. Such work could be done at a relatively low cost and could be performed at night to minimize the effect on traffic. Preliminary Designs
This table presents a summary of the reconstruction proposals of Caltrans and the four workshop teams. In making comparison be cautioned that the scope of work varies between the different proposals and the life cycle costs and the user costs have yet to be finalized. For example, while the Blue and Brown teams proposals show the lowest initial cost, the yellow team proposal may have a lower life cycle cost and the Green team proposal may result in the lowest user costs.
This table presents a summary of the reconstruction proposals of Caltrans and the four workshop teams. In making comparison be cautioned that the scope of work varies between the different proposals and the life cycle costs and the user costs have yet to be finalized. For example, while the Blue and Brown teams proposals show the lowest initial cost, the yellow team proposal may have a lower life cycle cost and the Green team proposal may result in the lowest user costs. PAVEMENT RENEWAL FOR URBAN FREEWAYS COST ANALYSIS SUMMARY LA-710 (LONG BEACH FREEWAY) by CALTRANS
GREEN: PCC solution 12" doweled PCC pavement over 14" of LCB (existing pavement recycled on site) BROWN: AC solution/Rubblize existing PCC and CTB and overlay with 8" of AC (Polymer) BLUE: Stone Matarix Asphalt (SMA) solution, ( 8 3/4" overlay) over existing PCC (localized repairs needed). YELLOW: PCC solution. Recycle existing 8" PCC and 8" of CTB and stabilize with cement and replace on subgrade (18" to 12"). Then place PCC pavement 12"(inside lanes) to 14" (outside lanes). Lessons Learned While many of the engineering ideas produced by the teams are still being analyzed, some very important "general principles" emerged:
David O. Cox is a senior engineer in FHWA's Office of Engineering. He deals with contract administration and innovative contracting techniques on a nationwide basis. He previously served as assistant division administrator in Tennessee, technical systems development engineer in Florida, and area engineer in Louisiana. Cox has a bachelor's degree in civil engineering from Oregon State University and a master's degree in civil engineering from Louisiana State University. He is a registered professional engineer in Louisiana.
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