Estimation of the Network Capacity for Multimodal Urban Systems (original) (raw)
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The growth of transportation networks and their increasing interconnections, although positive, has the downside effect of an increasing complexity which make them difficult to use, to assess, and limits their efficiency. On average in the UK, 23% of travel time is lost in connections for trips with more than one mode, and the lack of synchronization decreases very slowly with population size. This lack of synchronization between modes induces differences between the theoretical quickest trip and the 'time-respecting' path, which takes into account waiting times at interconnection nodes. We analyse here the statistics of these paths on the multilayer, temporal network of the entire, multimodal british public transportation system. We propose a statistical decomposition - the 'anatomy' - of trips in urban areas, in terms of riding, waiting and walking times, and which shows how the temporal structure of trips varies with distance and allows us to compare different cit...
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Exploring the Effect of Variability of Urban System Characteristics in the Network Capacity
Transportation Research Board 90th Annual MeetingTransportation Research Board, 2011
Mobility and transportation are two of the leading indicators of economic growth of a society. As cities around the world grow rapidly and more people and modes compete for limited urban space to travel, there is an increasing need to understand how this space is used for transportation and how it can be managed to improve accessibility for everyone. In a recent paper, Daganzo and Geroliminis (1) explored the connection between network structure and a network's MFD for urban neighborhoods with cars controlled by traffic signals and derived an analytical theory for the MFD using Variational Theory. Information needed to estimate this network MFD's are average network (total length of roads in lane-km, number of lanes, length of links), control (signal offsets, green phase and cycle time) and traffic (free flow speed, congested wave speed, jam density, capacity) characteristics. However in previous studies, Variational Theory has been applied only in cities with deterministic values of the above variables for the whole network and by ignoring the effect of turns. In our study we are aiming to generate an MFD for streets with variable link lengths and signal characteristics and understand the effect of variability for different cities and signal structures. Furthermore, this variability gives the opportunity to mimic the effect of turning movements and heterogeneity in drivers' behavior. This will be a key issue in planning the signal regimes such a way that maximizes the network capacity and/or the density range of the capacity.
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Frontiers in Future Transportation, 2020
The three-dimensional passenger macroscopic fundamental diagram (pMFD) describes the relation of the network accumulation of public transport and private vehicles, and the passenger production. It allows for modeling the multi-modal traffic dynamics in urban networks and deriving innovative performance indicators. This paper integrates this concept into a multi-modal transport system design framework formulated as a simulation-based optimization problem. In doing so, we consider the competition for limited road space and the operational characteristics, such as congestion occurrences, at the strategic design level. We evaluate the proposed framework in a case study for the Sioux Falls network. Thereby, we deliver a proof of concept, and show that the proposed methodology indeed designs a transport system which benefits the overall system's performance. This paper further advances the integration of sequential model-based optimization techniques, macroscopic traffic flow concepts...
Frontiers in Future Transportation, 2021
Interactions among different modes or vehicle classes in urban road networks affect the network performance in different and complex ways. Thus, an answer to the question of “how many cars are too many for a city?” is not trivial. However, multi-modal macroscopic fundamental diagrams (MFD) offer a novel opportunity to answer this question. So far, no methodology exists to estimate multi-modal MFDs resulting from arbitrary multi-modal interactions. In this paper, we propose a methodology to capture additional delays in the shape of the MFD and derive an approach for estimating multi-modal MFDs thereof. The influence on the MFD shape is established using the two-fluid theory of urban traffic by defining pairwise copula functions between travel times of each mode. In contrast to many existing approaches, the presented approach retains individual mode's speed information. We show the applicability of the approach with a tri-modal case of bicycles, buses, and cars with empirical data...
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Analysing the configuration of integrated multi-modal urban networks
This article proposes urban network models as instruments to assess the sustainable mobility performance of urban areas, thanks to their capacity to describe the detail of the local environment in the context of a wider city-region. Drawing from the features of existing street network models that offer disaggregate, scalable and relational analysis of the spatial configuration of urban areas, it presents a multi-modal urban network model that describes the urban environment using three systems – private transport (car, bicycle and pedestrian), public transport and land use. This model can be used to analyse the proximity, density and accessibility characteristics of urban areas for the individual or integrated network modes and land use activities, using a range of distance types and other analysis parameters. An implementation of the multi-modal urban network model is created for the Randstad city- region and is analysed to test its features and possibilities. In particular, the analysis of the configuration of the urban network according to different distance parameters, and the analysis of the integrated modes and land use, give indications to the successful use of integrated multi-modal urban networks to build a rich sustainable mobility profile of urban areas.
Journal of Systems Science and Systems Engineering, 2012
Traditional system optimization models for traffic network focus on the treatment of congestion, which usually have an objective of minimizing the total travel time. However, the negative externality of congestion, such as environment pollution, is neglected in most cases. Such models fall short in taking Greenhouse Gas (GHG) emissions and its impact on climate change into consideration. In this paper, a social-cost based system optimization (SO) model is proposed for the multimodal traffic network considering both traffic congestion and corresponding vehicle emission. Firstly, a variation inequality model is developed to formulate the equilibrium problem for such network based on the analysis of travelers' combined choices. Secondly, the computational models of traffic congestion and vehicle emission of whole multimodal network are proposed based on the equilibrium link-flows and the corresponding travel times. A bi-level programming model, in which the social-cost based SO model is treated as the upper-level problem and the combined equilibrium model is processed as the lower-level problem, is then presented with its solution algorithm. Finally, the proposed models are illustrated through a simple numerical example. The study results confirm and support the idea of giving the priority to the development of urban public transport, which is an effective way to achieve a sustainable urban transportation.