Abstract
A significant percentage of road fatalities and injuries occur in the nonmotorway rural road network. One of the main causes of accidents on these roads is represented by overtaking, as, by its nature, it involves a risk of a head-on collision with oncoming traffic. The paper describes a combined simulation approach (driving simulator and traffic microsimulation) designed to examine the influence of different traffic conditions on passing manoeuvres on two-lane two-way rural roads. The main focus was the evaluation of the end of the passing manoeuvre because it reflects the risk of a head-on collision. In addition, the study aimed to assess the usefulness of the proposed combined approach in the ability to proactively and quickly diagnose traffic safety problems and consequently to evaluate appropriate solutions. The data collected with an interactive driving simulator on a sample of 54 participants have been used to adjust some input data of the traffic microsimulation software. A specific situation consisting of a stationary heavy vehicle obstructing the entire lane was repeated in both experiments. The analyses focused on time-to-collision (TTC), defined as the remaining gap between the passing vehicle and the oncoming vehicle at the end of the passing manoeuvre. The results showed that the type of manoeuvre performed is significantly influenced by the traffic condition. Furthermore, the manoeuvre is influenced by the gap between two successive vehicles in the opposite lanes. Focusing on the end of the manoeuvre, it was found how a traffic increase leads to a significant reduction of the TTC values. Furthermore, the comparative analysis conducted between the data recorded following the combined approach and those obtained using exclusively the input data of the microsimulation software supports the usefulness of the proposed methodology for conducting road safety analyses, especially in complex traffic environments where drivers’ behaviour plays a decisive role.
Highlights
One of the main causes of accidents on these roads is represented by overtaking, as, by its nature, it involves a risk of a head-on collision with oncoming traffic. e paper describes a combined simulation approach designed to examine the influence of different traffic conditions on passing manoeuvres on two-lane two-way rural roads. e main focus was the evaluation of the end of the passing manoeuvre because it reflects the risk of a head-on collision
Most road accidents worldwide occur on rural roads. ey are associated with the highest risk of fatalities and serious injuries in the 41 OECD (Organization for Economic Cooperation and Development) countries [1] and accident data from other countries as the United States of America (USA) [2] and Australia [3] show comparable figures
While the lack of the ability to overtake may lead to the formation of large queues [6], the interaction with oncoming traffic flow from the opposite direction may significantly increase the risk of accidents, for example, due to the false temporal and distance estimations regarding the oncoming vehicles made by Journal of Advanced Transportation drivers [7,8,9,10]
Summary
Most road accidents worldwide occur on rural roads. ey are associated with the highest risk of fatalities and serious injuries in the 41 OECD (Organization for Economic Cooperation and Development) countries [1] and accident data from other countries as the United States of America (USA) [2] and Australia [3] show comparable figures. The advantages of both simulation tools could be fully used: the possibility of carrying out road safety analyses of complex situations on a considerable amount of data, using traffic microsimulator models whose parameters are representative of the drivers’ behaviour in the geographic area and driving conditions analysed 2. Research Objective and Motivation e purpose of this study is to evaluate the influence of different traffic-flow conditions on the occurrence of potential risk situations, which could lead to a crash event, during the passing manoeuvre on two-lane two-way rural roads, using a combined simulation approach. Several studies analysed the passing manoeuvres on this type of road, mainly based on field and driving simulation studies All these studies showed that one of the most critical factors involved in passing behaviour is the drivers’ ability to estimate the required gap for passing a lead vehicle in front of an oncoming one. E parameters that affect a single section are (1) mirror section identification (MirrorID); (2) available sight distance at the end of the passing zone (ASD) (m); and (3) sight distance factor (SDfactor)
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