Approximated Headway Distributions of Free-Flowing Traffic on Ohio Freeways for Work Zone Traffic Simulations

Abstract

Headway or interarrival time (IAT) data of successive vehicles in free-flowing traffic ahead of work zones for each lane on six different Ohio freeways (two with two lanes in one direction, three with three lanes, and one with four lanes) for 3 days were measured and analyzed. Approximated IAT distributions were generated as a function of the traffic volume for each lane, and relationships between traffic volumes and approximate cumulative IAT distributions were established; this allowed a direct conversion from hourly traffic counts to corresponding cumulative IAT distributions. On the basis of the validation of these IAT distributions with IAT data collected in an independent study, this conversion method produces fairly accurate cumulative IAT distributions for selected hourly traffic volumes. A set of cumulative IAT distribution spreadsheets may be downloaded at webce.ent.ohiou.edu/orite/cumulativeIATdistributions.html. It was also found that the same approximated cumulative IAT distribution can be used to model and simulate free-flowing traffic at other freeway locations in Ohio. It is not known whether these universal approximated IAT distributions would apply for freeways in other states.