Gerdien Klunder

Traffic flow effects of Integrated full-Range Speed Assistance (IRSA)

This paper discusses the assessment of the effects of integrated full-range speed assistance (IRSA), using the ITS modeller. The aim of IRSA is to assist drivers in their longitudinal driving task by providing speed advice or speed warnings and cruise control-like functionalities. The effects of the application of IRSA in three scenarios (approaching a traffic jam, approaching a reduced speed limit zone and leaving the head of a queue) are presented. Positive effects on throughput, safety and the environment were achieved. In addition, the paper discusses general aspects of modeling vehicle and driver behavior for co-operative systems, and how this is done in the ITS modeller.

Traffic monitoring and modeling for Intersection Safety

The INTERSAFE-2 project aims to develop and demonstrate a Cooperative Intersection Safety System that is able to significantly reduce injury and fatal accidents at intersections. The cooperative sensor data fusion is based on state-of-the-art and advanced on-board sensors for object recognition and relative localisation, a standard navigation map and information from other road users, infrastructure sensors and traffic lights. We created a traffic safety model for the INTERSAFE-2 system. The system incorporates a high level fusion module and local dynamic maps database that store static intersection topology. Furthermore, risk assessment from the infrastructure side has been performed in order to detect potentially dangerous situations, and to determine when the system should give a warning in order to prevent a possible collision. To evaluate the safety algorithm, video sequences of two intersections in Helsinki are used, which were processed with a generic tool for image processing and traffic monitoring.

Traffic Flow Impacts of Adaptive Cruise Control Deactivation and (Re)Activation with Cooperative Driver Behavior

In 2006 in the Netherlands, a field operational test was carried out to study the effect of adaptive cruise control (ACC) and lane departure warning on driver behavior and traffic flow in real traffic. To estimate the effect for larger penetration rates, simulations were needed. For a reliable impact assessment, the on- and off-switching of the system should be taken into account. Furthermore, because ACC systems are less cooperative than normal drivers, the reference behavior should include this cooperative behavior. In this research, cooperative driver models for normal drivers were developed as well as an ACC model that included on- and off-switching for the microscopic simulation environment known as the intelligent transportation systems modeler. Parameter settings were validated with data from the pilot. The results clearly show that on- and off-switching behavior has a large influence on traffic flow. This effect depends on the degree of congestion. In congestion, the effect of the ACC is larger. Without the possibility of switching it on and off, the ACC has a positive impact on throughput. However, when the ACC can be switched on and off, it has a negative impact on throughput.

Traffic data for local emissions monitoring at a signalized intersection

In order to assist planning efforts for air pollution-responsive dynamic traffic management (DTM) systems, this research assesses the accuracy of local emissions monitoring based on traffic data and models. The study quantifies the benefits of increased data resolution for short-term emissions estimates at a signalized intersection. The emissions estimates are also compared with air quality measurements in the immediate roadside environment. Results show that traffic-based emissions estimates require detailed knowledge of the local vehicle fleet and speed profiles. Traffic-based emissions monitoring enables pollution-responsive DTM, but these results indicate that this approach only applies over long time periods. This limit is due to the inherent stochasticity of vehicle arrivals and emissions rates. Using current tools, even detailed knowledge of on-road vehicles and traffic leaves uncertainty in short-term roadway emissions.

Evaluation Results of the Amsterdam, Netherlands, Practical Trial with In-Car Travel and Route Advice

Travel and route guidance services are widely available. Social navigation services that provide travelers with advice aimed at minimizing driver travel time, while also taking into account the effect on travel times of other travelers, are relatively new. Theoretically, social navigation has been shown to reduce total travel time by 10% to 30%. This paper presents the evaluation results of a large-scale field trial for pretrip and on-trip route advice with load balancing, in which about 20,000 participants were active. The evaluation provided insight into the potential effects of in-car information services, such as effects on user behavior, traffic flow effects, and technical aspects. Participants used mostly the pretrip advisories. Compliance with the on-trip route advice was 50%, which was considered high (compared with compliance with route advice on variable message signs). An effect on traffic flow could not be measured, as penetration rates were (despite thousands of users) still too low. An offline study using measured travel times combined with a traffic model, however, showed that substantial delay reductions can be achieved for the Amsterdam, Netherlands, region. Participants’ appreciation of the service resulted in a mixed picture with positive and negative ratings. The main practical contribution of this paper is that the results can be used to develop social navigation services. Empirical insights about route advice compliance can be seen as the main scientific contribution.

Improvement of Network Performance by In-Vehicle Routing Using Floating Car Data

This paper describes a study which gives insight into the size of improvement that is possible with individual in-car routing advice based on the actual traffic situation derived from floating car data (FCD). It also gives an idea about the required penetration rate of floating car data needed to achieve a certain degree of improvement. The study uses real loop detector data from the region of Amsterdam collected for over a year, a route generating algorithm for in-car routing advice, and emulated floating car data to generate the routing advice. The case with in-car routing advice has been compared to the base case, where drivers base their routing decisions on average knowledge of travel times in the network. The improvement in total delay using the in-vehicle system is dependent on penetration rate and accuracy of the floating car data and varies from 2.0% to 3.4% for 10% penetration rate. This leads to yearly savings of about 15 million euros if delay is monetarised using standard prices for value of time (VOT).

The effect of inaccurate traffic data for ramp metering: Comparing loop detectors and cameras using information utility

This paper introduces a topic which is of growing interest in the traffic control and management community, namely the relation between traffic data quality and the efficiency of traffic management. After some explanatory background and state of the art, it will become clear that no standard approach is available for traffic engineers to determine which accuracy of traffic data is needed for a certain traffic management application. In this paper we will show how the effect of inaccurate measurements on network level can be quantified by determining information utility functions. This approach is illustrated by presenting the results of a simulation study into the effect of inaccurate loop detector measurements on a ramp metering system. The relation between different accuracies of flow and speed measurements as input for a ramp metering system and the corresponding effect on the network performance is studied with a micro simulation model. The results of the simulation are used in a cost-benefit analysis for a case comparing loop detectors with camera measurements, where loop detectors are considered more accurate but also more expensive. We will show that higher measurement accuracy will lead to a better performance of the ramp metering system, resulting in a higher average network speed, and also quantify this relationship.

The potential of Connected Cruise Control in the Netherlands

This paper presents the in-car advisory system Connected Cruise Control. The system gives advice - which is determined in a central back office based on the traffic state - to the driver, in order to prevent or solve suboptimal traffic flow conditions. The system aims at optimal lane distribution in high flow conditions and a reduction of the capacity drop by advising drivers to maintain a short (but safe) headway at the end of a traffic jam. The system was implemented in a microscopic simulation tool to evaluate the potential benefits for different penetration and compliance rates. With the simulation results, insight is gained into the situations in which the system is most effective. With loop detector data from motorways and other major roads in The Netherlands it is analyzed how often the situations in which the system is most effective happen. This lead to an estimation of the potential of Connected Cruise Control in The Netherlands.