Evaluation of Interstate Highway Capacity for Short-Term Work Zone Lane Closures

The need to maintain adequate traffic flow through short-term Interstate work zones is paramount on today's heavily traveled freeways. Numerous states have policies related to traffic flow thresholds, vehicle delay, and vehicle queue lengths that provide guidance on conditions when shortterm lane closures can be instituted. Generally, traffic flow threshold limits are a function of traffic-stream characteristics, highway geometry, work zone location, type of construction activities, and work zone configuration. A research study was initiated in South Carolina to examine quantitatively the development and implementation of a methodology for use in determining an updated lane-closure policy based on statespecific parameters. The study focused on determining the number of vehicles per lane per hour that can pass through short-term Interstate work zone lane closures with minimal or acceptable levels of delay. Research tasks included a survey of policies of other states, field-data collection, and methodology development. A methodology was developed with field data collected from 22 work zone sites along South Carolina's Interstate system. Data were obtained during a 12-month period from September 2001 to August 2002. Data collection procedures and data analysis methods employed in model development are summarized. Results of this study may be helpful to state highway agencies interested in developing similar research-based policy guidelines for short-term Interstate lane closures in their jurisdictions.