November/December 2000 - Public Roads Magazine

Work zones may seem to be even more ubiquitous in the future because of a combination of factors. Much of the nation's current transportation infrastructure is reaching the end of its useful life, and after more than 40 years of a great road-building era, including the development of the Interstate Highway System, the focus for the future, according to Federal Highway Administrator Kenneth R. Wykle, will be on maximizing the performance of our surface transportation system by more efficiently maintaining and operating our National Highway System.¹

Despite the increasing frequency of work zones, the effects of work zones on a project are usually not considered until the design phase of the project. Moreover, user costs, such as delay caused by the work zone, are rarely considered during the planning and development of many projects. The consideration of the cost to the user in terms of delay over time in relation to the improvement in life expectancy may affect the project and may improve overall transportation decision-making.

The Strategic Work-Zone Analysis Tools (SWAT) program addresses work-zone factors and stresses the importance of accounting for work-zone influences when making transportation-improvement decisions. This initiative is focused on providing the tools that are necessary to achieve the goal of a more comprehensive analysis to support and enhance strategy development and decision-making in every phase of the project: planning, design, construction, and operations.

A suite of tools are being developed to meet the needs of practitioners. Practitioners throughout the country are helping the Federal Highway Administration (FHWA) to identify their needs and the appropriate tools. The practitioners are participating in data collection, tool development and testing, and delay-measurement development. The timetable for the availability of these tools has not yet been definitively determined.

The tools can be used independently or in combination. The suite of tools can be configured to support the different levels of analysis and the stages of development.

The decision-support analysis levels are represented by simple equations. These levels illustrate where we are with work-zone analysis and where we want to go. (See figure 1.) It is envisioned that the advanced levels (levels 4 through 6), which include work-zone factors, illustrate the levels of analysis that correspond to the decisions that are made during the planning, design, and construction of the project. The desired outcome is the incorporation of work-zone considerations throughout the entire project development cycle.

Figure 2 identifies three different tools, input data, and tool interactions. The basic inputs are data that describe transportation-network characteristics on a macroscopic level.

The first tool is the expert system. It is expected that the expert system will provide the preliminary work-zone strategy and phasing scenarios that will allow a work-zone analysis at the early stages of project development. However, the expert system could be used at any stage of development. The expert system will provide a list of possible strategies and phasing based on the description of a specific improvement. Like most expert systems, this development of the tool would be based on the experiences and practices of experts in work-zone strategy and phasing.

The next tool is the spreadsheet. The spreadsheet can support two analyses: traffic impacts and cost.

The traffic-impact analysis spreadsheet will provide a quick and general analysis. This spreadsheet will support the analysis of the static network capacity and will take into account the strategy to mitigate delays if mitigation factors are included in the spreadsheet data. Using the traffic-impact spreadsheet, practitioners will be able to investigate alternative work-zone strategies and phasing for various improvements. Work-zone factors will be interpolated for an average day and by year for the estimated improvement life cycle. Daily effects will provide information concerning various strategies and phasing effectiveness. Life-cycle delay costs will provide decision-makers with a parameter by which to compare various improvements. The spreadsheet outputs will indicate traffic conditions and effects that users will experience over time and will provide input into the cost analysis.

The cost-analysis spreadsheet will convert traffic-impact parameters into costs. The costs will be adjusted over time and combined with other costs to produce an amount that indicates the total cost of each alternative improvement. Unit costs of each alternative will be identified. Sensitivity analyses between alternative costs can provide insight into possible alternative performances and can support informed improvement selections.

The third tool of this suite responds to the need for detailed modeling or simulation analysis. A model or simulation will be modified to support detailed analysis of a specific work-zone strategy and phasing.

The first function is to provide delay-mitigation factors for the traffic-impact analysis spreadsheet to facilitate the general analysis. The model can supply factors for general mitigation strategies and phasing that cannot be obtained from other analysis methods or guides, such as the Highway Capacity Manual (HCM), and are not readily apparent to analysts.

The second function is to use the model to supply situation-specific mitigation factors. Supplying specific mitigation factors will enable practitioners to obtain precise estimates of effects directly related to their situations.

The last function is to support the development of traffic-impact information to facilitate the operation of work-zone motorist information systems. Work-zone motorist information systems can inform motorists of expected delays and identify less congested alternative routes.

As illustrated in figure 3, combining the decision-support analysis levels and the tools of the suite provides an overall initial picture of work-zone analysis. The spreadsheet alone can be used to support levels 1 through 4, depending on the data available. Up to a level-4 analysis could be used to support decisions during the improvement planning stage. Levels 5 and 6 can be reached by combining the spreadsheet with a model or simulation modified for work-zone analysis. The detailed analysis capabilities of levels 5 and 6 will support the decision-making needs associated with improvements at the design, construction, or operation stages of development. If you combine the spreadsheet or the model or both with the expert system, you enhance the effectiveness of each analysis by supporting the creation of work-zone strategy and phasing options. At any stage, the expert system would support alternative analysis and aid in comparing the proposed strategy with others that may not have been considered.

QuickZone - Work-Zone Delay-Estimation Tool Development
by Karl Wunderlich

The first tool to be developed through the SWAT program is the traffic-impact spreadsheet, called QuickZone. The target release time is March 2001, but interim versions will be available for testing and evaluation. QuickZone will provide a quick, general, and flexible work-zone impact analysis that will enhance decision-making in all phases of project development.

The QuickZone concept provides an easy-to-use, easy-to-learn tool that uses software tools that are familiar to our target users - state and local highway construction, operations, and planning staff and construction contractors. Our current approach is to develop QuickZone as a Microsoft Excel Workbook application. The prospective QuickZone analyst need only have Excel97 or higher running on a Windows-operated computer with minimal memory and processing-speed requirements. Our desired standards to provide rapid results are less than one hour to input and check a QuickZone network and less than three minutes to analyze the data and produce delay profiles over the project duration.

QuickZone will perform the following functions in urban and inter-urban settings:

Quantify corridor delay resulting from capacity decreases in work zones.
Identify delay impacts of alternative project phasing plans.
Support tradeoff analyses between construction costs and delay costs.
Examine impact of construction staging by location along mainline, time-of-day (peak vs, off-peak), and season (summer vs. winter).
Assessment of travel-demand measures and other delay-mitigation strategies.
Support the setting of work-completion incentives.

A prototype Project Delay Summary from QuickZone, featuring: (1) A graph depicting the projected average delay (in vehicle-hours) by time of day. Each line represents the profile for a particular phase of the project. This graph will be helpful in identifying which phases are likely to be the primary generators of delay during the life of the construction project. (2) In the upper right-hand corner, a table showing total average daily delay (vehicle-hours) for each phase. (3) In the lower right-hand corner, a table showing the maximum length (in vehicles) of the mainline queue for each graph. This figure can be used to compute maximum user delay or to determine if the mainline queue grows beyond some key position.
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Dr. Karl Wunderlich is a senior principal analyst at Mitretek Systems Inc., a not-for-profit systems engineering firm based in McLean, Va. Since 1992, he has worked in support of FHWA and the Intelligent Transportation Systems (ITS) Joint Program Office (JPO) on research efforts dealing with the quantitative assessment of ITS impacts through modeling and simulation. He is co-author of Integrating ITS into the Planning Process: Seattle Case Study, nominated for "Best Research Project (2000)" by the Intelligent Transportation Society of America. He holds a bachelor's degree in industrial engineering from Northwestern University and both a masters degree and a doctorate in industrial and operations engineering from the University of Michigan.

Two data-collection efforts are underway to support the development of SWAT. The first effort, which is taking place now, is collecting data that will be used to perform a preliminary delay-measurement analysis and will support the validation and testing of the different tools. The second collection effort will focus on delay measurement and will develop new insights into the measurement of travel delay and will support development of delay measures and performance guidelines. The second, more detailed effort will be conducted in the summer or fall of 2001.

The first data-collection effort is being conducted in conjunction with the development of the spreadsheet. FHWA has solicited for participants to collect data from actual work zones in an effort to create four work-zone data sets that will support tool validation. Data concerning before and during work-zone operation, travel time/delay, volume, queue lengths, and alternative-mode demand will be collected.

The detailed delay-measurement data-collection effort will be conducted separately after the preliminary delay-measurement/tool-validation data collection. The lessons learned from the preliminary data collection will provide insights concerning the scope of the detailed effort. Detailed data collection will be conducted at locations with existing advanced data-collection capabilities. The detailed data collection will support the identification of better and more realistic delay measurements and the development of performance guidelines. The realistic delay measurements and performance guidelines will be created to support and extend performance-based contracting to include the operation of work zones.

Over time, the SWAT program will deliver various tools and guidance concerning the independent or interactive use of the tools. The tools developed and delivered will be dependent on the priorities of the product team and the steering committee and on available resources. The two data collection efforts will provide data that supports tool development, delay measurement development, and performance guidance. The desired outcome is that in the near future, work-zone effects will be identified, estimated, and accounted for throughout the improvement development process and when making transportation improvement decisions. This will result in better transportation decision-making, the reduction of work-zone delay, and an increase in work-zone safety.

For more information about SWAT or QuickZone, contact Deborah Curtis at FHWA's Turner-Fairbank Highway Research Center by telephone at (202) 493-3267 or by e-mail at deborah.curtis@fhwa.dot.gov.

Reference
Kenneth R. Wykle. "Developing an Operations Vision," Public Roads, Vol. 63, No. 5, Federal Highway Administration, Washington, D.C., March/April 2000.

John Harding is a transportation specialist with FHWA's Office of Operations Technology Services. His experience is in research and development of various intelligent transportation system technologies and has concentrated on the development of advanced transportation management systems. In his career at FHWA, he managed a program that identified and transferred sensor technology for use in transportation, led the Specialty Vehicles Platform of the Intelligent Vehicle Initiative, and developed the Intelligent Transportation System (ITS) Deployment Analysis System, and currently, he is the manager of the Strategic Work-zone Analysis Tools program. Harding worked for the New Jersey Department of Transportation, Virginia Department of Transportation, and the MITRE Corp. He holds a bachelors degree in civil engineering and a master's degree in public administration.