Optimal Timing for Lane(s) Addition to an Existing Highway: A Benefit–Cost Approach

The present study presents a comprehensive framework for optimal highway capacity expansion through lane(s) addition. The applicability of the proposed framework is demonstrated using data from a multi-lane urban arterial. In the proposed methodology, annualized widening costs (agency lane addition cost and work zone user delay cost) and excess user costs for do-nothing scenario (excess travel delay cost, excess vehicle operating cost and excess crash cost) were estimated for each analysis year within highway life cycle to estimate a range of traffic volumes for highway capacity expansion. Furthermore, a sensitivity analysis was conducted to evaluate the sensitivity of optimal time for highway capacity expansion to: (1) annual traffic growth rates (2) agency to user cost relative weights and (3) annual discount rate. Study results revealed that optimal highway capacity expansion time corresponds to an ADT ranging between approximately 34,430 and 37,600 vehicles per day for the case study traffic mix conditions. The sensitivity analysis results revealed that increase in agency to user cost relative weight and annual traffic growth rate would result in later and earlier optimal highway capacity expansion, respectively, while variations in annual discount rate have minimal impact on optimal highway capacity expansion timings. It is anticipated that the application of proposed framework can result in a sustainable decision by saving a huge amount of agency expenditures and excess user costs due to non-optimal decisions.