Real-time traffic state estimation is of importance for efficient traffic management. This is especially the case for traffic management systems that require fast detection of changes in the traffic ...conditions in order to apply an effective control measure. In this paper, we propose a method for estimating the traffic state and speed and density, by using connected vehicles combined with stationary detectors. The aim is to allow fast and accurate estimation of changes in the traffic conditions. The proposed method does only require information about the speed and the position of connected vehicles and can make use of sparsely located stationary detectors to limit the dependence on the infrastructure equipment. An evaluation of the proposed method is carried out by microscopic traffic simulation. The traffic state estimated using the proposed method is compared to the true simulated traffic state. Further, the density estimates are compared to density estimates from one detector-based method, one combined method, and one connected-vehicle-based method. The results of the study show that the proposed method is a promising alternative for estimating the traffic state in traffic management applications.
Interchange stations with their many connecting modes and lines are central for a high-quality public transport system. Bus access at the station needs to operate reliably and efficiently in order to ...prevent congestion and queues. To this end, a conceptual simulation model for evaluation of bus terminal operations is presented in this paper. It is based on discrete event simulation and able to describe the detailed movements and interactions that occur between vehicles at larger terminals. The model has a modular approach, where common spatial sections at terminals are represented by modules that can be easily combined into many different terminal layouts. An implementation of the model is presented and, as a first sensitivity test, applied in a numerical experiment representing Norrköping interchange station in Sweden. The results indicate that the model can be a useful tool in planning processes.
The control algorithm used for deciding on the speed limit in variable speed limit systems is crucial for the performance of the systems. The algorithm is designed to fulfil the purpose of the ...variable speed limit system, which can be one or several of the following aspects: increasing safety, increasing efficiency and decreasing environmental impacts. Today, many of the control algorithms used in practice are based on fixed thresholds in speed and/or flow. Therefore, they are not necessarily reflecting the current traffic conditions. Control algorithms with a greater level of complexity can be found in the literature. In this paper, four existing control algorithms are investigated to conclude on important characteristics affecting the performance of the variable speed limit system. The purpose of the variable speed limit system and, consequently, the design of the control algorithm differ. Requirements of the investigated control algorithms are that they should be easy to interpret and the execution time should be short. The algorithms are evaluated through microscopic traffic simulation. Performance indicators related to traffic safety, traffic efficiency and environmental impacts are presented. The results show that the characteristics of the variable speed limit system and the design of the control algorithm will have effect on the resulting traffic performance, given that the drivers comply with the variable speed limits. Moreover, the time needed to trigger the system, the duration and the size of speed limit reductions, and the location of the congestion are factors of importance for the performance of variable speed limit systems.
Microscopic simulation of pedestrian traffic is an important and increasingly popular method to evaluate the performance of existing or proposed infrastructure. The social force model is a common ...model in simulations, describing the dynamics of pedestrian crowds given the goals of the simulated pedestrians encoded as their preferred velocities.
The main focus of the literature has so far been how to choose the preferred velocities to produce realistic dynamic route choices for pedestrians moving through congested infrastructure. However, limited attention has been given the problem of choosing the preferred velocity to produce other behaviors, such as waiting, commonly occurring at, e.g., public transport interchange stations.
We hypothesize that: (1) the inclusion of waiting pedestrians in a simulated scenario will significantly affect the level of service for passing pedestrians, and (2) the details of the waiting model affect the predicted level of service, that is, it is important to choose an appropriate model of waiting.
We show that the treatment of waiting pedestrians have a significant impact on simulations of pedestrian traffic. We do this by introducing a series of extensions to the social force model to produce waiting behavior, and provide predictions of the model extensions that highlight their differences. We also present a sensitivity analysis and provide sufficient criteria for stability.
•Extensions to the social force model to include waiting pedestrians are proposed.•Simulations of interactions between waiting and passing pedestrians are performed.•Predictions of the models are characterized and the differences are analyzed.•Sufficient criteria for the stability of the models are given.•The choice of waiting model is showed to significantly impact simulation results.
This paper presents a micro-simulation model that takes flared design of rural intersections into consideration. The intersection model is designed with input parameters that describe the geometric ...conditions of the flare. The behavior model includes both a traditional gap-acceptance sub-model and a passage model for modelling of vehicles’ possibility to pass other vehicles using the flare. The intersection model developed has been implemented in the traffic micro simulation model RuTSim. The gap-acceptance part of the model has been calibrated using data for stop and yield 3-way intersections. The validation was performed by using video recordings to calculate delay for the yield regulated intersection and time in queue and service time for the stop regulated intersection. The results from the validation simulations correspond well with the empirical validation data. The effect of the flare on delay has been studied by using 3 different intersection lay-outs and different levels of minor and major flow. The result shows that the delay is decreasing with increasing intersection radius.
Adaptive cruise control (ACC) can potentially improve quality-of-service and safety and reduce the environmental effect of the road traffic system. This article uses vehicle trajectories from traffic ...simulation to study effects of ACC on vehicle acceleration and deceleration rates. The analysis is based on traffic simulations with car-following models including ACC functionality and driver behavior in ACC-equipped as well as standard nonequipped vehicles. The simulation results show that ACC can improve the traffic situation in terms of reduced acceleration and deceleration rates even though macroscopic traffic properties may remain uninfluenced. This supports the hypothesized positive road safety and environmental effects of ACC. It is also established that the results are largely dependent on the assumptions made regarding driver behavior in ACC-equipped and standard vehicles. It is consequently crucial to include appropriate assumptions regarding driver behavior in traffic simulation-based analyses of ACC.
Almost all studies of sleepy driving are carried out in driving simulators and with monotonous road conditions (no interaction with other cars). The present study investigated indicators of sleepy ...driving in a more challenging scenario after a night awake. 17 participants drove a high fidelity moving base driving simulator experiment while sleepiness was monitored physiologically and behaviourally. Short periods of situations of free driving (no other vehicles) alternated with short periods of following another vehicle (car following) with and without the possibility to overtake. The result showed that a night of prior sleep loss increased sleepiness levels at the wheel (eye closure duration and lateral variability) compared to after a night of normal sleep. Blink duration while overtaking was significantly lower compared to the other situations, it was at the same level as after night sleep. Speed when passing a stopped school bus was not significantly affected by sleepiness. However the warning caused a more rapid reduction of speed. In conclusion, a moderately challenging driving contest did not affect sleepiness indicators, but a very challenging one did so (overtaking). This suggests that it is important to monitor the driving situation in field operational tests of sleepy driving.
<p data-select-like-a-boss="1">Variable speed limit (VSL) systems are used to improve the traffic conditions by adjusting the speed limits based on the current traffic situation. Advances in vehicle ...technology have made it possible to use connected vehicles in VSL systems. Connected vehicles can continuously transmit information about their speed and location, which can be used to estimate the current traffic conditions at arbitrary locations. In this study, we propose a VSL system based on connected vehicles. The aim is to also allow application of VSLs for non-recurrent bottleneck mitigation at arbitrary locations, unlike today's systems which require densely placed detectors or are limited to beforehand known bottleneck locations. The proposed system is evaluated by microscopic traffic simulation. The results indicate that the VSL system manage to improve traffic efficiency in a simulated incident scenario.
•A cooperative variable speed limit system is proposed.•Infrastructure to vehicle communication and autonomous vehicle control are used.•Potential benefits are studied by the use of microscopic ...traffic simulation.•The system contributes to flow harmonization and reduced exhaust emissions.•There are no adverse effects of the system on the mean speed on the road.
Variable speed limit systems where variable message signs are used to show speed limits adjusted to the prevailing road or traffic conditions are installed on motorways in many countries. The objectives of variable speed limit system installations are often to decrease the number of accidents and to increase traffic efficiency. Currently, there is an interest in exploring the potential of cooperative intelligent transport systems including communication between vehicles and/or vehicles and the infrastructure. In this paper, we study the potential benefits of introducing infrastructure to vehicle communication, autonomous vehicle control and individualized speed limits in variable speed limit systems. We do this by proposing a cooperative variable speed limit system as an extension of an existing variable speed limit system. In the proposed system, communication between the infrastructure and the vehicles is used to transmit variable speed limits to upstream vehicles before the variable message signs become visible to the drivers. The system is evaluated by the means of microscopic traffic simulation. Traffic efficiency and environmental effects are considered in the analysis. The results of the study show benefits of the infrastructure to vehicle communication, autonomous vehicle control and individualized speed limits for variable speed limit systems in the form of lower acceleration rates and thereby harmonized traffic flow and reduced exhaust emissions.
Variable speed limit (VSL) systems are used to improve the traffic conditions by adjusting the speed limits based on the current traffic situation. Advances in vehicle technology have made it ...possible to use connected vehicles in VSL systems. Connected vehicles can continuously transmit information about their speed and location, which can be used to estimate the current traffic conditions at arbitrary locations. In this study, we propose a VSL system based on connected vehicles. The aim is to also allow application of VSLs for non-recurrent bottleneck mitigation at arbitrary locations, unlike today's systems which require densely placed detectors or are limited to beforehand known bottleneck locations. The proposed system is evaluated by microscopic traffic simulation. The results indicate that the VSL system manage to improve traffic efficiency in a simulated incident scenario.
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