Network Performance Degeneration in Dynamic Traffic Assignment

EVAQ is a traffic model for ex-ante evaluations of evacuations plans. The model is still in development and it is uncertain whether EVAQ will accurately model network performance degeneration. At the same time it can be said that accurate network performance degeneration is very important for evacuations. The research of this thesis identifies that there are phenomena that contribute to network performance degeneration that are not modelled. Two important phenomena that are not included are the flow degeneration as soon as links become congested and the constraints that nodes (intersections) themselves have. Several general ideas were thought up to implement these phenomena. A selection was made on the basis of accuracy. Flow degeneration as soon as a link becomes congested has to do with the link model. The link model determines what number of vehicles can potentially enter and leave the link within a time step. In order to accurately determine these, the framework of Cell Based Queuing is developed. It represents the queue on a link as a set of cells that are related to successive time steps in the past. The theory of kinematic waves is applied which explains that in congestion the traffic states move upstream. Traffic states in the cells can thus be determined using the link outflow from the past. Link inflow is determined by the remaining storage capacity on the link. As an addition to the theory of kinetic waves, the cell at the end of the link is governed by saturation flow rather than kinematic waves. This implicitly applies a capacity drop. A newly developed node model evaluates constraints on the nodes. The new node model is a combination of these constraints and the constraints by link inflow that are already evaluated. The node model exists out of several sub models that are used for different node types. The controlled intersection model deals with combined use of conflict areas and the effect of green phases. The uncontrolled intersection model is based on a capacity formula that determines the capacity for a minor flow based on a major flow. The formula is used in a framework that relates all flows on the intersection. For roundabouts an existing model by Cetur (1986) is used. A similar framework is put in place to relate all flows over the roundabout. The model is adapted to work on lane level rather than link level for turbo roundabouts. For weaving sections, on-ramps and off-ramps a new model is developed that looks at lane specific demand. The new model needs more calculation time but produces more precise capacity estimations. Significant changes are found for the MFD and for queue lengths (spillback). The latter now resembles results from the microscopic model VISSIM quite closely and needs both the new link and node model. The new node and link model are part of the Dynamic Network Loading model of EVAQ. This model has been the centre of most changes performed for EVAQ and can be used in any other Dynamic Traffic Assignment model. Furthermore, the model is theory based and can thus be used for reversed engineering and more extensive analysis of bottlenecks, also for evacuation schemes.Transport & PlanningCivil Engineering and Geoscience

Development, Simulation and Evaluation of In-car Advice on Headway, Speed and Lane

With the use of Advanced Driver Assistance Systems (ADAS), traffic efficiency may be improved. This thesis presents an advisory system using advice on headway, speed and lane, in order to prevent potential problems 1-2km downstream. Current systems operate on smaller scale (e.g. Adaptive Cruise Control) or larger scale (e.g. route advice). With advice it is possible to redistribute traffic over the lanes more optimally, reduce disturbances from lane changes, reduce the capacity drop by making drivers more active at the end of congestion, and to reduce/delay spillback. With simulation it is shown that travel time delay may be reduced by 40-50%. However, also a few negative side effects are found, such as the increased spillback from congestion on an off ramp as traffic has been advised towards the right-hand lane for an upstream lane drop on the left side. Providing advice at the end of congestion to make drivers more attentive, shows to be very effective on its own.Transport & PlanningCivil Engineering and Geoscience

An urban traffic extension of a freeway driver model for use in the OpenTraffic® open source traffic simulation

This paper presents an extension of a microscopic freeway driver model for urban traffic. As urban traffic is more complex than freeway traffic, and because scientific models require extensive development, scientific models are often limited to freeways. For urban studies commercial software is often used. Models describing the behaviour in commercial software are only known to researchers into a limited extent, making them unsuitable for driver behaviour studies. Commercial software is therefore often used for studies on traffic control or safety. This paper fills some of the gap for urban driver behaviour models. Adaptations to the freeway model include an additional lane change incentive regarding intersections and an increased willingness to accelerate. New sub-models are presented for traffic lights and priority conflict. The latter includes courtesy yielding, yielding for priority traffic and keeping conflicts clear. If these models are combined with models for other modes such as public transport, cyclists and pedestrians and with realistic traffic light controllers, driver behaviour in urban traffic becomes an accessible subject for simulation research.Transport & PlanningCivil Engineering and Geoscience

A generic multi-scale framework for microscopic traffic simulation part II: Anticipation Reliance as compensation mechanism for potential task overload

The inclusion of human factors (HF) in mathematical models is proving crucial to allow complex driving behaviour and interactions to be explicitly considered to capture driving phenomena. An important area where such integration is required is for the role of anticipation by drivers to compensate for critical traffic situations. In this paper, we introduce the concept of Anticipation Reliance (AR), which acts as a demand lowering compensative effect for the driving task by relying more on anticipation. We implement AR in a generic multi-scale microscopic traffic modelling and simulation framework to explore and explain the effects of HF on traffic operations and safety in critical traffic situations. This concept addresses a disparity in the description of driver workload in relation to the execution of driving tasks in regard to the confidence that drivers place on tasks that are sub-consciously catered for. The crossover from HF to a mathematical description of this role of AR introduces a ground-breaking concept that explains and models the mechanisms that allow drivers to compensate and avoid accidents in many circumstances, even when driving errors or sub-optimal driving performance occurs. By and large, the HF effects can be subdivided in effects on perception and anticipation; effects on sensitivity and response to stimuli; and effects on personal attributes and characteristics. A key aspect of the framework are two intertwined driver-specific mental state variables—total workload and awareness—that bridge between classic collision-free idealized models for lane changing and car following, and HF models that explain under which conditions the performance of drivers deteriorates in terms of reaction time, sensitivity to stimuli or other parameters. In this paper, we focus on the awareness construct, as described by AR, and explore the effects. We prove the effectiveness of the approach with a case example that demonstrates the ability of the model to dissect a complex traffic situation with both longitudinal and lateral driving tasks, while endogenously considering human factors and that produces accident avoidance and occurrence within the same order of magnitude compared to real traffic accident statistics.Transport and Plannin

LMRS: An integrated lane change model with relaxation and synchronization

Transport & PlanningCivil Engineering and Geoscience

Evaluation and modelling of the traffic flow effects of truck platooning

With automated and cooperative driving making its breakthrough, and related systems in fast development, their future influence and impact on roads and traffic may be extensive. Truck platooning is such an application that relies on the development of Cooperative Adaptive Cruise Control (CACC) and is said to be practice ready. While the main advantages of truck platooning lie in emission and energy reduction, claims are also being made for the influence on traffic flow. In this paper, we pose hypotheses based on some of the main claims. We also attempt to substantiate and give quantitative proof of the potential effects of truck platooning on traffic flow performance. The simulation model LMRS-IDM+ is extended to encompass the main influencing dynamics related to potential effects of truck platooning, based on empirical findings. The effects of truck platooning were tested for the influence of traffic states, truck gap settings, platoon sizes, and the share of equipped trucks. This resulted in outcomes regarding the total traffic performance, the performance of traffic at ramps, and the ability of a platoon to remain platooning as part of a case experiment performed on a part of the Trans-European ITS Corridor. The results showed that truck platooning may have a small negative effect on the total non-saturated traffic flow, however with a much larger negative effect on saturated traffic flow. However, drivers may be reluctant to platoon in saturated traffic in any case. The ability of inflowing traffic to merge at on-ramps was found to be affected by truck platoons, with platoon disengagements occurring under various conditions. The applied gap settings for platooning trucks did not significantly affect the merge time, while a higher gap did lead to a higher number of disengagements. The ability of trucks to platoon was positively affected by a greater percentage of equipped trucks and by larger platoon sizes. Shorter gap times also slightly improved the ability of trucks to remain in platooning formation. Finally, recommendations are given to improve platoon strategies and for policymakers to only allow truck platooning outside of busy (near-) saturated traffic, even though drivers may be reluctant to use the system in these conditions. Also, recommendations are made to investigate potential differences in the effects between the European and American contexts for truck-platooning.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Transport and Plannin

Will automated vehicles negatively impact traffic flow?

With low-level vehicle automation already available, there is a necessity to estimate its effects on traffic flow, especially if these could be negative. A long gradual transitionwill occur frommanual driving to automateddriving, inwhichmany yet unknown traffic flow dynamics will be present. These effects have the potential to increasingly aid or cripple current road networks. In this contribution, we investigate these effects using an empirically calibrated and validated simulation experiment, backed up with findings from literature.We found that low-level automated vehicles in mixed traffic will initially have a small negative effect on traffic flow and road capacities.The experiment further showed that any improvement in traffic flow will only be seen at penetration rates above 70%. Also, the capacity drop appeared to be slightly higher with the presence of low-level automated vehicles. The experiment further investigated the effect of bottleneck severity and truck shares on traffic flow. Improvements to current traffic models are recommended and should include a greater detail and understanding of driver-vehicle interaction, both in conventional and in mixed traffic flow. Further research into behavioural shifts in driving is also recommended due to limited data and knowledge of these dynamics.Transport and Plannin

Empirical analysis of an in-car speed, headway and lane use Advisory system

For a recently developed in-car speed, headway and lane use advisory system, this paper investigates empirically advice validity (advice given in correct traffic circumstances), credibility (advice logical to drivers) and frequency. The system has been developed to optimize traffic flow by giving advice on a tactical scale. This scale allows traffic flow improvement and fills a gap as most ITS which aim to optimize traffic flow operate on the operational or strategic scale. Using log files of the actual system for a period of two weeks, the validity, credibility and frequency of advices is determined. Validity is not guaranteed as the advices are determined based on a predicted traffic state due to data delay and as the advices are based on the predicted traffic state 1 minute in the future. Given that the advisory system is a first in its kind, a new methodology was developed to assess the system, based on the use of virtual trajectories and defining indicators to assess, validity, credibility and frequency. The analysis shows that many advices are indeed valid and credible, but some are not, allowing room for improvement. Advice frequency is found to be reasonable. The analysis also shows that in-car filtering of advices, i.e. merging equal advices, is important to lower the frequency.Transport & PlanningCivil Engineering and Geoscience

Unravelling effects of cooperative adaptive cruise control deactivation on traffic flow characteristics at merging bottlenecks

Cooperative Adaptive Cruise Control (CACC) systems have the potential to increase roadway capacity and mitigate traffic congestion thanks to the short following distance enabled by inter-vehicle communication. However, due to limitations in acceleration and deceleration capabilities of CACC systems, deactivation and switch to ACC or human-driven mode will take place when conditions are outside the operational design domain. Given the lack of elaborate models on this interaction, existing CACC traffic flow models have not yet been able to reproduce realistic CACC vehicle behaviour and pay little attention to the influence of system deactivation on traffic flow at bottlenecks. This study aims to gain insights into the influence of CACC on highway operations at merging bottlenecks by using a realistic CACC model that captures driver-system interactions and string length limits. We conduct systematic traffic simulations for various CACC market penetration rates (MPR) to derive free-flow capacity and queue discharge rate of the merging section and compare these to the capacity of a homogeneous pipeline section. The results show that an increased CACC MPR can indeed increase the roadway capacity. However, the resulting capacity in the merging bottleneck is much lower than the pipeline capacity and capacity drop persists in bottleneck scenarios at all CACC MPR levels. It is also found that CACC increases flow heterogeneity due to the switch among different operation modes. A microscopic investigation of the CACC operational mode and trajectories reveals a close relation between CACC deactivation, traffic congestion and flow heterogeneity.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Transport and Plannin

Pleasure in using adaptive cruise control: A questionnaire study in The Netherlands

Objective: Adaptive cruise control (ACC), a technology that allows for automated car following, is becoming increasingly prevalent. Previous surveys have shown that drivers generally regard ACC as pleasant but that they have to intervene when the ACC reaches its operational limits. The former research has been mostly concerned with specific car brands and does not fully reflect the diversity of ACC types in traffic today. The objective of the present research was to establish the determinants of pleasure in using ACC. Methods: A 55-item online questionnaire was completed by Dutch users of diverse ACC systems. Results: Respondents (N = 182) rated their ACC highly, with a mean score of 8.0 on a scale from 1 (extraordinarily negative) to 10 (extraordinarily positive) and were most pleased with ACC on high-speed roads and in low-density traffic. Moreover, the findings point to specific operational limits such as associated with cut-in situations. Pleasure was greater for the types of ACC that are able to decelerate to a full stop, according to 48% of our sample. An analysis of the free-response items indicated that respondents who were displeased with ACC mentioned its occasional clumsiness and the dangerous situations it may evoke, whereas those who were pleased with ACC valued the complementarity of human and machine and emphasized the roles of responsibility and experience in using ACC. Conclusion: Pleasure in using ACC is a function of both technological advances and human factors.Biomechatronics & Human-Machine ControlTransport and PlanningTransport and Plannin