Transport - road safety

Numerous Advanced Driver Assistance Systems (ADAS) are already available on the market whilst the development of new systems continues, including asystem to support overtaking manoeuvre performance. Overtaking manoeuvrescause many fatal accidents each year. Before ADAS can be introduced to assist drivers with overtaking, a study into acceptance and behavioural consequences is necessary, presented in this paper. The overtaking manoeuvre is studied in a driving simulator on a normal rural carriageway with two traffic lanes, in three conditions. Firstly, a control condition in which the participants in the experiment were motivated to overtake if needed and possible. In the second condition occasionally special 2km overtaking tracks were announced and inserted. Thirdly, the electronic overtaking assistant was activated, supporting the drivers in their decisions with respect to feasibility to overtake at any moment. Both supporting conditions were appreciated, and the contours of an ele...

Observations of overtaking manoeuvres on two-lane rural roads were carried out to enhance the understanding of driver behaviour prior to, during and after an overtaking manoeuvre. An instrumented vehicle was driven with different speeds while other vehicles' overtaking manoeuvres were recorded and analysed afterwards. The differences in duration of overtaking manoeuvres between different overtaking strategies and different speeds of the vehicle that was overtaken, turned out to be small. Fairly short perception-reaction times were observed, indicating that the decision to perform an overtaking manoeuvre is made before an appropriate gap in the oncoming traffic stream is available.

Gap acceptance is a process that occurs in different traffic situations, such as to cross a road, to enter a roundabout or to perform an overtaking maneuver on a bi-directional road. The minimum gap that a driver will accept is generally called the critical gap. Mathematical representations of the gap acceptance process are an important part of for instance traffic simulation models. For a more realistic representation, these mathematical descriptions have become more complex, including behavior parameters, such as ‘impatience’ or ‘aggressiveness’. Since these parameters influence gap acceptance behavior, they should therefore be included in critical gap distribution estimations. This paper presents a new simulation-based approach to estimate distribution of critical gaps. The proposed, so called, KS-GA method enables estimation of other behavior parameters simultaneously with the critical gap distribution parameters. The approach is based on minimization of the Kolmogorov-Smirnov distance between the simulated and observed accepted gaps, and the simulated and observed rejected gaps. The optimization is performed using a Genetic Algorithm. By applying the approach to synthetic data, the model is verified. The estimation results of the KS-GA method are comparable to the performance of the maximum likelihood procedure; a well accepted and frequently applied critical gap distribution estimation method. If intra-driver changes are included, the KS-GA method performs better. The KS-GA method is applied using real life overtaking gap acceptance data on a bi-directional two-lane road.

Observations of overtaking maneuvers on bi-directional rural roads were carried out to enhance the understanding of driver behavior prior to, during and after an overtaking maneuver. Data were collected to serve as a basis for developments towards overtaking assistance systems. An instrumented vehicle was used to record overtaking maneuvers: this vehicle drove in actual traffic and several speeds were chosen that led to other vehicles overtaking the instrumented vehicle. In total, 48 maneuvers were recorded and analyzed afterwards. The duration of the overtaking maneuvers was analyzed in relation to the applied overtaking strategy and the speed of the instrumented vehicle. Only limited variation in the overtaking duration was found, from which it is concluded that a single type of overtaking assistance system can serve most drivers. Fairly short perception-reaction times were observed, indicating that the decision to perform an overtaking maneuver is made before an appropriate gap in the oncoming traffic stream is available. Overtaking assistance can therefore only be valuable if it is able to assist prior to the emergence of such a gap, otherwise valuable time is lost.

This paper shows results of an observation of overtaking frequencies on roads with opposing traffic. This observation is a first step of research regarding potential safety effects of advanced driver assistance systems on overtaking on two lane rural roads. We determine overtaking frequencies as a function of flow rates on both directions, distinguishing different vehicle types. Observed overtaking frequencies are lower than overtaking demand, especially when the directional split becomes more equal. Therefore we recommend adding directional split to the equation to calculate overtaking frequency.

This paper presents the results of a cost-effectiveness study concerning the effects of an overtaking prohibition on two lane rural roads. Overtaking prohibitions are being implemented in the Netherlands aiming to improve safety. Overtaking frequency on road sections with and without overtaking prohibition are measured by means of camera observations Overtaking frequencies were determined by comparing the order of vehicles at the start and end of a road segment without junctions. Overtaking actions were assessed by means of changes in the order of the vehicles. This was done for road segments without overtaking prohibition and similar road segments with overtaking prohibition. It turns out that up to ten percent of drivers performs overtaking manoeuvres on normal road sections. On sections with prohibition, about one percent of drivers disobey this traffic rule. Additionally, a questionnaire was sent to drivers of one of the observed roads, with questions about the overtaking prohibition. 28 percent of the respondents indicated that they will not always comply with an overidable overtaking prohibition. The discussion of the results will be focused on cost effectiveness of an overtaking prohibition for improving road safety on rural roads. The results of the observation, together with the results of the questionnaire are used to discuss the possibilities of the four E's, education, enforcement, engineering and electronics to solve the safety problems of overtaking on rural roads. For the covering abstract see ITRD E136183.

Advanced driver assistance systems (ADAS) are available on the market whilst the development of existing systems and new systems continues. Improving safety is one of the key purposes of these systems. ADAS would therefore be welcome to support overtaking manoeuvres, since these cause many fatal accidents each year. Before an ADAS could be developed that can assist drivers with overtaking a thorough task analysis of overtaking is necessary and presented in this paper. The overtaking manoeuvre is divided in five phases, in which more than 20 subtasks are distinguished. Next, possibilities of ADAS towards overtaking are verified. Almost all subtasks of an overtaking manoeuvre can be assisted with existing ADAS functionalities, combined in a so-called active overtaking assistant. Unfortunately, for the more complex subtasks such as ‘judging the distance with the first opposing vehicle’ and ‘monitoring the deviations of the lead vehicle’ no ADAS functionality is available yet. (A)

Intelligent Speed Adapt ion (ISA) is a system that limits vehicles at the speed limit. Research in Sweden, England and the Netherlands has shown that it has a positive impact on safety. The current study compares traffic flows under ISA with those in the presence of regular traffic lights. The model results show that ISA is able to replace traffic lights at crossroads with a clear main flow. This important positive effect will improve the support for ISA, which was originally designed for safety reasons. (A) For the covering abstract of the conference see ITRD E206647.

Intelligent Speed Adaptation (ISA) is a system that limits vehicles at the speed limit. Research in Sweden, England and the Netherlands has shown that it has a positive impact on safety. The current study compares traffic flows under ISA with those in the presence of regular traffic lights. The model results show that ISA is able to replace traffic lights at crossroads with a clear major flow. This important positive effect will improve the support for ISA, which was originally designed for safety reasons. For the covering abstract see ITRD E123876.