Overtaking behaviour of vehicles on undivided roads in non-lane based mixed traffic conditions

Traffic on Indian roads is highly mixed in nature with wide variations in the static and dynamic characteristics of vehicles. These vehicles do not follow strict lane discipline and occupy any available lateral position on the road space. Overtaking is one of the most complex and important manoeuvre on undivided roads where the vehicles use the opposing lane to overtake the slower vehicles with the presence of oncoming vehicles from opposite direction. They are unavoidable especially in the case of mixed traffic conditions where there is always a speed difference between the fast and slow moving vehicles. Overtaking process involves lane-changing manoeuvres, acceleration and deceleration actions and estimation of relative speed of overtaking and overtaken vehicles, and also, estimation of speed and distance of the oncoming vehicle. The main objective of the present study is to study the overtaking characteristics of vehicles on undivided roads under mixed traffic conditions. For this purpose, details of overtaking data were collected on a two-lane two-way undivided road using moving car observer method and registration plate method. The overtaking characteristics of all types of vehicles under mixed traffic conditions were observed and mathematically modelled. The data extracted and analysed were the acceleration characteristics, speeds of the overtaking vehicles, overtaking time, overtaking distances, safe opposing gap required for overtaking, flow rates, overtaking frequencies, types of overtaking strategy, and types of overtaking and overtaken vehicles. Two types of overtaking strategies were observed in the field such as flying overtaking and accelerative overtaking. Graphs were plotted between the relative speed of the overtaking and overtaken vehicles against the overtaking time and negative correlation was found between the speed differential and total overtaking time for all categories of vehicles. It was observed that the number of overtaking increases with increase in the flow rate in the on-going direction and decreases with increase in flow in the opposite direction, The results obtained from this study will be useful to understand the overtaking behaviour of vehicles in mixed and non-lane discipline traffic conditions. These parameters will be useful in the development of traffic simulations models for undivided roads and thereby for estimation of capacity. The findings from the study can also be used to estimate potential collision times which will be helpful to improve the road safety.

Modeling lateral placement and movement of vehicles on urban undivided roads in mixed traf?c:A case study of India

In India,the majority of urban roads are undivided where the behavior of flows in a particular direction is predominantly influenced by the opposing traffic.Due to lack of lane segregation,the vehicles in ongoing direction occupy the opposing lane,which increases the lateral interactions between vehicles.These lateral interactions are influenced by various parameters such as vehicle types,driver behavior and vehicular speeds.Study of such complex interactions plays an important role in evaluating various management measures using microscopic simulation models.The lateral characteristics of vehicles,such as placement,separation and movement,act as necessary input for simulation models.The present study aims to analyze and model the lateral characteristics of vehicles on two-lane urban undivided roads.To achieve this,traffic flow data were collected from an urban undivided mid-block section in Bangalore City,India,using video graphic technique.Multiple linear regression model was developed for predicting the lateral placement of subject vehicle and it was found that lateral placement of subject vehicle is influenced by types and speeds of subject and opposing vehicles.Lateral separation for different types of ongoing(subject)and opposing pairs was also analyzed.The results show that both the ongoing and opposing vehicles have less freedom to move laterally when their sizes increase and hence,lateral separation decreases.The choice of path of vehicles’lateral shifts(left,current and right)on urban undivided roads was modeled using multinomial logistic regression.Lateral shift of a vehicle is influenced by speeds of subject vehicle and leader vehicle in current path,speed of leader vehicle in target path,and lateral gap between leader vehicles in current path and target path.