The Construction Congestion Cost System (CO3) is an integrated set of tools to estimate the impact of traffic maintenance contract provisions on congestion, road user cost, and construction cost. We use CO3 to produce realistic budgets and select practical contracting methods that provide an acceptable balance between construction cost and congestion. 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 provides examples that illustrate the CO3 model and methods. CO3 models the common characteristic of construction work zones by which road capacity can vary from hour to hour as lanes close and open and work conditions change. Traffic demand also varies with time of day, and drivers may divert to an alternate route or cancel trips because of delays caused by construction. CO3 estimates traffic delay due to traffic congestion as a function of demand and capacity and it estimates traffic cancellations and diversions as functions of traffic delay.

This is a smaller version of CO3 Traffic Demand, Delay, and User Cost Model, reduced to meet the 10,000 word limit of the ASCE Journal.


Robert I. Carr, Ph.D., P.E.
Professor of Civil Engineering
Department of Civil and Environmental Engineering
2340 G. G. Brown
University of Michigan
Ann Arbor, MI 48109-2125
(734) 764-9420 Fax: 764-4292


congestion, delay, demand, backup, construction, user cost, traffic, queue, work zone, alternate route


1998 by R. I. Carr. Submitted to ASCE Journal of Construction Engineering and Management, May, 1998. (This is single-spaced version), 20 pp.

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CO3 System Components, for Downloading

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