Better Roads

August 2013

Better Roads Digital Magazine

Issue link:

Contents of this Issue


Page 9 of 84

RoadScience other, sometimes generating rancor. What is not arguable is that LCCA is a process of selecting the most economical pavement design based on initial construction costs and future maintenance, rehabilitation and reconstruction costs. LCCA is a process for evaluating transportation project expenditures. "LCCA will assist in determining the best – the lowest-cost – way to accomplish the project," says FHWA's Life Cycle Cost Analysis Primer (2002). The five steps to LCCA, according to the primer, are • Establish design alternatives. • Determine activity timing. • Estimate costs (agency and user). • Compute life cycle-costs, and • Analyze the results. Significantly, best-practice LCCA calls for including not only direct agency expenditures (for example, construction or maintenance activities), but also costs to facility users that result from these agency activities. "The predicted schedule of activities and their associated agency and user costs form the projected life-cycle cost (LCC) stream for each design alternative," FHWA says. "Using an economic technique known as 'discounting,' these costs are converted into present dollars and summed for each alternative. The analyst can then determine which alternative is the most cost-effective." FHWA notes the lowest LCC option may not necessarily be implemented when other considerations such as risk, available budgets, and political and environmental concerns are taken into account, adding "LCCA provides critical information to the overall decision-making process, but not the final answer." Although LCCA was only officially mandated in a very limited number of situations, FHWA has always encouraged the use of LCCA in analyzing all major investment decisions where they are likely to increase efficiency and effectiveness. However, the 1998 Transportation Equity Act for the 21st Century (TEA-21) removed the requirement for state highway agencies to conduct LCCA on high-cost NHS useable project segments. But the philosophy lives on. A 2011 National Cooperative Highway Research Program project – NCHRP No. 703: Guide for Pavement Type Selection (Google NCHRP No. 703) – surveyed state transportation agencies and reported that 29 of 35 states that responded use LCCA for new construction or reconstruction projects. Because there is no current requirement that LCCA be conducted or used to select among pavement types used on federally funded highway projects, federal LCCA guidance and assistance to state transportation agencies is advisory. Beginning in August 2012 – in an effort to shine a light on a process that could cause federal funds to be spent more wisely, and to fulfill a mandate of MAP-21 – the Government Accountability Office (GAO) looked closely at use of LCCA among the states. The result is the June 2013 report, Improved Guidance Could Enhance States' Use of Life-Cycle Cost Analysis in Pavement Selection (Google GAO-13-544). GAO visited four states to interview local FHWA, state DOT and asphalt and concrete pavement industry association representatives, and conducted telephone interviews with state transportation agency officials in 12 more states. Selection criteria includes a wide range of LCCA approaches and a wide geographical distribution of states. GAO found a mixed bag, with no great lessons to learn. "Information gathered from these states is not generalizable to all states," GAO reports. "States' life-cycle cost analysis practices vary, though they are often informed by FHWA guidance. Most of the selected states we reviewed use LCCA in some capacity to help ensure the long-term cost-effectiveness of investment decisions. "Thirteen of 16 states included in our review used it in some capacity," GAO says. "State transportation officials in [those] 13 states indicated that the goal of LCCA was to help ensure that the agency makes long-term, cost-effective investment decisions. Some state officials also noted that LCCA could help the state transportation agency communicate to stakeholders – pavement industry representatives, state legislators, and taxpayers – that it is making sound decisions." Mechanistic-Empirical Design Even as LCCA evolves, with a strong shove by AASHTO, the "hands on" mechanistic-empirical design philosophy is taking root in road agencies from coast to coast. The Mechanistic-Empirical Pavement Design Guide, Interim Edition: A Manual of Practice provides more reliable pavement designs for all pavement types, based on in-service conditions, according to ARA, creator of the MEPDG. The guide and associated software – now in various stages of adoption throughout the state DOTs – provide a state-of-practice mechanisticempirical highway pavement design methodology based on actual experience from the real world, translated to a design program (see "To Prevent Failure, Begin with Better Bases," May 2013, pp. 20-27). Pavement ME Design is the next generation of AASHTOWare pavement design software, which builds upon the mechanistic-empirical pavement design guide, and expands and improves the features in the accompanying prototype computational software. Using real-world conditions, the MEPDG represents a major change in the way pavement design will be performed, and in a way, is not unlike of the Superpave system of performance-based mix design specs. Mechanistic-empirical are big words that describe a very simple concept. "Mechanistic" refers to the interaction 8 August 2013 Better Roads RoadScience_BR0813_old.indd 8 8/1/13 10:54 AM

Articles in this issue

Archives of this issue

view archives of Better Roads - August 2013