Investigating Drivers’ Headway in Iran Freeways

Received Sep2015 Received in revised Sep 2015 Accepted in September 2015 Headway is known as one of the most important basis for traffic studies which is widely used in road safety studies. Headway is known as suitable criteria for evaluation of drivers’ behavior. Therefore, in this paper, drivers’ behavior in Iran's freeways has been investigated based on headway data and its distribution functions. The required data are collected from Iran freeways base sections. Headway data of the congested flow and before queue has been filtered by the means of car following models and flow speed drop. Using the filtered data, headway distribution is estimated and the reliability of models has been evaluated. The lognormal model, due to having all characteristics of reliability, is the most comprehensive model. As a result, based on headway risky and the headway of more than 50% of vehicles is less than minimum safe headway in congested flows.