| 1. |
- Johansson, Fredrik
(författare)
-
Microscopic Modeling and Simulation of Pedestrian Traffic
- 2013
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Walking is an environmentally friendly and important mode of transportation. It constitutes the first and last part of almost any trip, regardless of what the main mode of transport is, and is especially important in connection to public transport trips.When designing public transport stations, and similar facilities with large and varying volumes of pedestrian traffic, it is advantageous to be able to predict the traffic conditions at the facility before it is built; discovering too late that the traffic at the facility is inefficient and perceived as uncomfortable may be very costly. To make these predictions we need accurate quantitative models of pedestrian traffic.The foundation of this thesis is the development of a microsimulation platform for pedestrian traffic, the Pedestrian Traffic Simulation Platform (FTSP). The platform is based on the Social Force Model (SFM) and intended for evaluation of proposed designs of pedestrian facilities. A contribution of this thesis is a thorough documentation of the implementation of the FTSP.An extensive literature review of previous research on the SFM revealed gaps in the methodology used to study the properties of the SFM and to interpret its results. This thesis proposes local performance measures to fill this gap. These measures are based on properties of the SFM, and enable quantitative analyses of the quality of service at pedestrian facilities. The proposed measures are applied to the simulation results of some basic scenarios, which reveal previously unknown properties of the SFM. These properties can be used to test the accuracy of the SFM.Another gap in the literature was how to include waiting behavior in the SFM. This thesis shows that accurate modeling of waiting pedestrians is important for the accuracy of the simulation results, and proposes three different extensions to the SFM to model waiting behavior.
|
|
| 2. |
- Johansson, Fredrik, 1983-
(författare)
-
Microscopic Simulation of Pedestrian Traffic
- 2016
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- There has recently been a renewed interest in planning for pedestrian traffic, primarily in connection to public transport interchange stations, since these are important for public transport to constitute an attractive alternative to car usage. This thesis concerns microscopic simulation of pedestrian traffic, which is a promising tool for analyzing and predicting the traffic situation in a given pedestrian facility; particularly powerful when the traffic is congested. Important applications of microscopic simulation include comparison of possible infrastructure designs such as proposed interchange stations, and evaluations of various traffic management solutions, for example information systems.The purpose of this thesis is to advance the capabilities of pedestrian microsimulation toward a level at which it can be reliably applied for quantitative analysis by practitioners in the field. The work is based on an established microscopic model of pedestrian dynamics, the Social Force Model (sfm), and the advances are made in a number of different areas.To be able to evaluate and compare simulated traffic situations suitable performance measures are needed. A set of local performance measures are proposed that quantifies the local delay rate density and estimates the discomfort perceived by the pedestrians.The sfm is extended to include waiting pedestrians through the introduction of a waiting model, demonstrated to be stable and free from oscillations. The inclusion of waiting pedestrians in the model is critical for accurate modelling of public transport interchange stations, where large groups of waiting pedestrians may hinder passing pedestrians if the design of the station is poor.The relaxation time of the adaptation to the preferred velocity is an important parameter in force based models of pedestrian traffic since it affects several behaviors of the simulated pedestrians, two of which are linear acceleration and turning movements. A comparison of observations of accelerating pedestrians reported in the literature and new observations of turning pedestrians indicates that no value of the relaxation time can give model behavior consistent with both sets of observations. This indicates that modifications of the model is needed to accurately reproduce the observed behavior.An important input to simulations is the preferred speed of the simulated pedestrians. The common assumption that the preferred speed distribution at a location does not vary during the day is tested through observations of pedestrian traffic at Stockholm Central Station. The results demonstrate that the preferred speeds are lower in the afternoon than in the morning, implying that the preferred speed should be treated as a source of uncertainty when applying pedestrian microsimulation.Finally, a sensitivity analysis of a simulation of the lower hall of Stockholm Central Station is performed to find the most important sources of uncertainty in the model predictions, given the available data. The results indicate that the uncertainty related to calibration is the largest of the considered potential error sources.
|
|
| 3. |
- Grumert, Ellen
(författare)
-
Cooperative Variable Speed Limit Systems : Modeling and Evaluation using Microscopic Traffic Simulation
- 2014
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- During the last decades the road traffic has increased tremendously leading to congestion, safety issues and increased environmental impacts. As a result, many countries are continuously trying to find improvements and new solutions to solve these issues. One way of improving the traffic conditions is by the use of so called intelligent transport systems, where information and communication technologies are being used for traffic management and control. One such system commonly used for traffic management purposes are variable speed limit systems. These systems are making use of signs to show speed limits adjusted to the prevailing road or traffic conditions. The rapid development in telecommunication technologies has enabled communication between vehicles, and between vehicles and the infrastructure, so called cooperative systems. This opens up for the possibility to further improve the performance of a standard variable speed limit system by adding cooperative system features.The overall aim of this thesis is to investigate the potential benefits of incorporating infrastructure to vehicle communication and autonomous control to an existing variable speed limit system. We show how such a cooperative variable speed limit system can be modeled and evaluated by the use of microscopic traffic simulation. Results from the evaluation indicate increased flow harmonization in terms of narrowing of the acceleration rate distribution and reduced exhaust emissions.Further, we compare four control algorithms for deciding on speed limits in variable speed limit systems. Differences in the resulting traffic performance between the control algorithms are quantified by the use of microscopic traffic simulation. It is concluded that the dened objective for the algorithms have a decisive influence on the effects of the variable speed limit system.The results from this thesis are useful for further development of variable speed limit systems, both with respect to incorporating cooperative features and by improving the speed setting control algorithms.
|
|
| 4. |
- Fu, Jiali
(författare)
-
Logistics of Earthmoving Operations : Simulation and Optimization
- 2013
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Earthworks are a fundamental part of heavy construction engineering and involve the moving and processing of the soil surface of earth. Normally, earthmoving operations are carried out during the early stages of heavy construction projects. To a large extent, the success of the fundamental earthmoving determines the sequence of the remaining parts of a project. Furthermore, the operations require expensive heavy equipment as well as manpower. Thus, improving the efficiency of earthmoving operations is a primary target from the point of view of the project management.This thesis develops simulation and optimization methods for logistics of earthmoving operations. Modeling earthmoving operations correctly is essential to ensure the credibility of simulation, and the well-known CYCLONE modeling methodology is employed to represent the earthmoving logistics. Discrete event simulation techniques are used to capture the interaction between resources and the randomness of the earthmoving activities. A prototype has been developed (Paper I) to demonstrate that the capability of the simulation system of evaluating alternative operating strategies and resource utilizations for earthmoving operations at a detailed level, as well as conducting productivity estimation and Total Cost of Ownership (TCO) calculations. The simulation system is then integrated with optimization to solve the optimal fleet selection problem for earthmoving operations (Paper II and III). Two optimization objectives are formulated and solved using the proposed simulation-based optimization framework and a genetic optimization algorithm: TCO minimization and maximization of productivity. The case studies show that the proposed mechanism can effectively allocate an optimal equipment combination for earthmoving operations and hence serve as an efficient tool for construction management. The main aim of the integrated simulation-based optimization platform is to act as a sales tool to help customers optimize their fleet and eventually their sites.In addition to the simulation-based optimization framework for earthmoving logistics, the thesis examines the possibility of reducing fuel consumption for articulated haulers which are the most fuel consuming machines in earthmoving (Paper IV). Fuel consumption has become one of the main focuses for automobile manufacturers and several studies have been carried out over the last years to evaluate the possibility of using topographical information and positioning systems to aid look-ahead control systems for road vehicles. Based on the assumption of available road slope information and positioning system, an optimal control problem is formulated to determine the optimal gear shift sequence and time of shifting. Model Predictive Control algorithms together with Dynamic Programming techniques are employed to solve the optimal gear shifting problem. Computer simulations show that both fuel consumption and travel time can be reduced simultaneously. In addition, the optimal gear shift sequence resembles the behavior of an experienced driver.
|
|
