Developing Travel Time-volume Functions for Two-way Two-lane Rural Highways in Iran

Travel time - volume relationships are widely used in traffic engineering and transportation planning. These relations obtained for different geometric and traffic conditions, are used in level of service analysis and traffic assignment models. The different highway physical, environmental and traffic characteristics invalidate the use of foreign regulations’ models. Therefore, to obtain native models and calibrating them seems to be necessary. This research aims to propose travel time - volume models in three regions of two lane two way highways in Iran; level, rolling and mountainous, using field and simulation data, simultaneously. Due to lack of adequate traffic data, especially in volumes near capacity, a simulation approach was deployed, and TWOPAS was used to generate the data. Data analysis was led to travel time-volume models in different terrains. Various statistical tests have shown the validity and accuracy of the obtained models. The obtained model is expressed as a combination of linear part (for v/c below 0.6) and nonlinear part (for v/c over 0.6). These models are more compatible with the experimental data and are thus able to better represent the behavior of traffic streams on Iranian roads.