By Chris Rundall, P.E., LEED AP

civil-engineeringI know A+B Bidding has been around for awhile, but I didn’t have a reason to research it until recently.  I was discussing alternative approaches to construction bidding with a local contractor in Steamboat Springs, and he mentioned this approach to project bidding:


 A + B x (the daily cost) = Contractor’s bid for evaluation of the lowest successful bidder

A = Contractor’s total bid for work items | B = Number of calendar days required to complete work


The daily cost represents the resultant delay cost. It takes into consideration traffic volumes, travel time and percentage of trucks.  CDOT’s Road User Cost Calculator can be helpful with this calculation.  It computes user costs based on predicted travel times.

The bidder with the lowest overall combined bid (A+B) is awarded the contract.  In the actual contract, the contractor will only be reimbursed for unit items (A).  The time allowed to complete the project is set at the bidder’s time component (B).  Incentive and disincentive provisions may also be used to ensure early completion and discourage unbalanced bidding.

Not all projects are great candidates for the A + B Bidding approach.  For example, Washington State’s DOT has defined criteria to consider before using it.  They advise that when the allowable traffic restrictions indicate only one way to perform the project, their designers should state the allowable contract time.   CDOT doesn’t have similar criteria for A+B Bidding.