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It is assumed that car-following behaviour is the same in different lanes of traffic flow, but it is necessary to investigate whether car-following behaviour in all lanes, in congested and non-congested conditions, is the same or not. For this purpose, the traffic data for a freeway in Iran (the Tehran–Qom freeway) were investigated. The results showed that by choosing the lane closer to the median, driving cautiousness will be reduced. This finding can not only be attributed to increasing speed, which is the characteristic of a lane closer to the median, but also occurs with time headway reduction. In other words, closer lanes to the median have higher speed and lower headway that will increase the capacity of these lanes. These results suggest that driving behaviour can be categorised based on the lane that the drivers select. Results also indicate that the capacity difference between inner and outer lanes is from about 7% up to 24%.

Lane change (LC) is one of the main maneuvers in traffic flow. Many studies have estimated LC duration directly by using lane-based data. The current research presents an estimate of LC duration for overtaking maneuver in nonlane-based traffic flow. In this paper, the LC duration is estimated implicitly by modeling lateral speed and applying the length of required lateral movement to complete the LC maneuver. In lateral speed modeling, the local linear model tree is applied which consists of three variables: the initial lateral distance, longitudinal speed, and time to collision (TTC), which itself is a function of the relative speed of follower and the distance between the two vehicles. The initial lateral distance is the relative transverse distance from which the following vehicle initializes the LC. The range of lateral speed was estimated between 0.5 and 5 km/h, which resulted in the LC duration between 2.5 and 24 sec. The results indicate that the lateral and longitudinal speed would be inversely related, while the lateral speed and the initial transverse distance as well as TTC would be directly related. The findings also indicate that TTC can be assumed as the most important factor affecting lateral speed. TTC at 8 sec can be considered as the threshold for its effect on the LC duration since at longer TTCs, and the lateral speed has remained almost constant. When TTC is longer than 8 sec, it would not affect the LC duration.

While time headway (TH) is a relatively simple variable and has been well researched, it has been less explored in non-lane-based traffic. The main aim of this paper is considering lateral distance in studying TH in a non-lane-based traffic flow. In this study driving behavior, speed-TH relationship, and the following threshold by using only TH in a non-lane-based flow were investigated. In a novel approach, THs were segmented into five intervals in a step by step manner from smallest to largest THs. Considering lateral distance led to divide driving behavior into intervals (based on the average TH), including: Unsafe (0-0.7 sec), non-lane-based car-following (0.9 sec), lane-based car-following (1.0 sec), overtaking TH (1.3 sec), and free driving (larger than 2.5 sec). It was founded that the TH of starting overtaking maneuver can be a good criterion to distinguish between following and free driving behavior. Also, in lane-based car-following behavior, when lateral distance between the following and preceding vehicles was not considerable, the smallest THs were seen. It has happened around the average speed of the flow as the driver may adopt lower THs because of the tendency to overtaking. Linear relationship was found between TH and lateral distance in non-lane-based car-following conditions. TH of non-lane-based behavior is less than lane-based and smaller THs would force drivers to apply lateral distance or vice versa.