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Robert I. Carr, Ph.D., P.E.
Professor Emeritus of Civil Engineering
Department of Civil and Environmental Engineering
University of Michigan
Ann Arbor, MI
(734) 665-8287, Fax 665-1737
Email: RICarr@RICarr.com, RICarr@umich.edu


The CO3 System is a tool with which engineers can estimate the magnitude and impacts of traffic congestion, including its cost impact on road users that can be expected during a construction project. Its name comes from the first two letters of COnstruction COngestion COst, on which the system focuses. CO3 was developed with financial support from the Michigan Department of Transportation, which is using it to reduce the impact of highway construction on Michigan travelers. From project conception through drafting provisions for maintaining traffic, CO3 provides a useful way for engineers to include construction congestion and its costs to users as an important variable in all project decisions.

CO3 measures the impact of congestion in two basic ways: (1) variables such as delay, diverted vehicles, and backup measure different characteristics of congestion and (2) user cost provides a common unit of measure with which to sum traffic impacts and compare them with construction cost. User costs consist of direct costs of increased travel distance due to traffic diversions and indirect costs that measure the impact of traffic delays and trip cancellations caused by congestion. In addition, CO3 provides a tool by which we can estimate and document project cost for alternative ways of maintaining traffic and changes in construction they require. We then use CO3 to compare user cost and construction cost of each alternative to help us select the best project alternative. Therefore, CO3 helps us select among alternative methods of maintaining traffic during construction, and it helps us select contract period costs for contract provisions that provide incentives for reducing congestion impacts during construction.

In parallel with CO3, CO3Flag calculates traffic impact and user cost of congestion from flagging operations. This congestion occurs when one lane of a two-lane road is closed and traffic alternates in direction under the control of a flagger, signal, or other control at each end of the work zone.

CO3 Papers for Downloading

CO3 Traffic Demand, Delay, and User Cost Model, April, 1998 (Adobe Acrobat file of 396 Kb). This paper describes the underlying CO3 model of traffic demand, delay, and user cost, particularly the methods by which CO3 calculates traffic backup and delay, diverted and cancelled trips, and road user cost. It is a companion paper to Construction Congestion Cost (CO3) (below).

Construction Congestion Cost (CO3) Basic Model, ASCE Journal of Construction Engineering and Management, March/April, 2000, pp 105-113. (Adobe Acrobat file of 228 Kb). This is a smaller version of CO3 Traffic Demand, Delay, and User Cost Model (above) reduced to meet the 10,000 word limit of the ASCE Journal.

Construction Congestion Cost (CO3) Traffic Impact and Construction Cost, ASCE Journal of Construction Engineering and Management, March/April, 2000, pp 114-121 (Adobe Acrobat file of 186 Kb). This paper demonstrates computation of impacts associated with alternative methods of maintaining traffic during construction.

CO3 System Components, for Downloading

CO3 User Manual is the complete 250 page guide to using CO3 and its software, including CO3Flag. It is provided in two forms:

CO3_Man.pdf (Adobe Acrobat file of 2,118 Kb) can be read and printed using Adobe Acrobat Reader. Adobe Acrobat Reader can itself be downloaded at this site. This is the recommended format for downloading.

CO3_Man.prn (Postscript file of 5,312 Kb) can be directly printed on a Postscript printer.

CO3 Software is now in two forms. "CO" is the standard CO3 file for Excel and "COFlag" is the CO3Flag file for Excel.

CO.xls (685 Kb)

COFlag.xls (659 Kb)

Readme.txt provides the latest information on software versions.

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This page last updated 11/18/2009, by RICarr