Journal: Transportation Research Procedia

Abbreviation

Publisher

Elsevier

Journal Volumes

ISSN

2352-1465

Description

Filters

2014 - 2019212020 - 20253
Reset filters

Search Results

Publications1 - 10 of 24
  • The influence of slope on walking activity and the pedestrian modal share
    Item type: Journal Article
    Meeder, Mark; Aebi, Tobias; Weidmann, Ulrich (2017)
    Transportation Research Procedia
    The aim of this paper is to research the relation between the slope of the terrain and walking activity, an area that has so far been little researched in transportation science. With the use of pedestrian counts from a busy and steeply sloped street as well as public transport ridership data, the effect of the inclination on the pedestrian modal share is researched. The results show a significant influence of slope on walking attractiveness, which is quantified by representing the walking modal share with a logit model. The model parameters acquired by maximum likelihood estimation suggest that a 1% increase in slope makes a walk roughly 10% less attractive. This value corresponds well with the small number of literature sources that exist on the same topic. The results were obtained with “live” data, acquired in the built environment rather than in a controlled experimental setting. Since this means that the exact origins and destinations or trip purposes of travelers cannot be fully known, the authors express reservation in interpreting the results.
  • Combining Macro- and Microscopic Approaches to Model Commercial Transport Demand in an Urban Area
    Item type: Conference Paper
    Reiffer, Anna; Heilig, Michael; Szimba, Eckhard; et al. (2020)
    Transportation Research Procedia
    Demand modeling of commercial transport has lagged behind private passenger demand modeling as a result of insufficient data sources and the complex types of movement. At a supra-regional level, commercial trips are usually conducted by heavy trucks. However, studies in urban areas show that only about 40% of all commercial trips are conducted by heavy vehicles, while the other 60% is conducted by light vehicles, indicating that this is not freight travel. Even though commercial transport has been somewhat regarded in recent research, most models focus on either freight trips or trips conducted to provide a service. However, for assessing policy sensitivity, all parts of commercial transport need to be considered. The model we present regards all aspects of commercial transport by assessing the parts separately. We distinguish between vehicles with variable and fixed daily. We further differentiate vehicles with fixed daily schedules into vehicles with short and long supply chains while focusing on the latter. To regard the entire supply chain of delivery vehicles we a combined macroscopic approach to obtain transit flows on a European level with a microscopic approach that is used to distribute the obtained packages of an urban area within said areas. The results of both the macroscopic and microscopic parts of the model are compared to traffic count data. The comparison of values show that the combination of macroscopic and microscopic model parts can model vehicles of commercial transport with a long supply chain, however, more attention should be regarded to the microscopic distribution.
  • A parking-state-based transition matrix of traffic on urban networks
    Item type: Conference Paper
    Cao, Jin; Menendez, Monica (2015)
    Transportation Research Procedia
    The urban parking and the urban traffic systems are essential components of the overall urban transportation structure. The short- term interactions between these two systems can be highly significant and influential to their individual performance. The urban parking system, for example, can affect the searching-for-parking traffic, influencing not only overall travel speeds in the network (traffic performance), but also total driven distance (environmental conditions). In turn, the traffic performance can also affect the time drivers spend searching for parking, and ultimately, parking usage. In this study, we propose a methodology to model macroscopically such interactions and evaluate their effects on urban congestion. The model is built on a transition matrix describing how, over time, vehicles in an urban area transition from one parking-related state to another. With this model it is possible to estimate, based on the traffic and parking demand as well as the parking supply, the amount of vehicles searching for parking, the amount of vehicles driving on the network but not searching for parking, and the amount of vehicles parked at any given time. More importantly, it is also possible to estimate the total (or average) time spent and distance driven within each of these states. Based on that, the model can be used to design and evaluate different parking policies, to improve (or optimize) the performance of both systems. A simple numerical example is provided to show possible applications of this type. Parking policies such as increasing parking supply or shortening the maximum parking duration allowed (i.e., time controls) are tested, and their effects on traffic are estimated. The preliminary results show that time control policies can alleviate the parking-caused traffic issues without the need for providing additional parking facilities. Results also show that parking policies that intend to reduce traffic delay may, at the same time, increase the driven distance and cause negative externalities. Hence, caution must be exercised and multiple traffic metrics should be evaluated before selecting these policies. Overall, this paper shows how a parking-state-based transition matrix, despite its simplicity, can be used to efficiently evaluate the urban traffic and parking systems macroscopically. The proposed model can be used to estimate both, how parking availability can affect traffic performance (e.g., average time searching for parking, number of cars searching for parking); and how different traffic conditions (e.g., travel speed, density in the system) can affect drivers ability to find parking. Moreover, the proposed model can be used to study multiple strategies or scenarios for traffic operations and control, transportation planning, land use planning, or parking management and operations.
  • Explaining socially motivated travel with social network analysis
    Item type: Journal Article
    Guidon, Sergio; Wicki, Michael; Bernauer, Thomas; et al. (2018)
    Transportation Research Procedia
    It has been hypothesized that a crucial factor to understand and explain socially motivated leisure travel is understanding the spatial distribution of individuals’ contacts. Still, only little is known about their actual link. Egocentric social network analysis (SNA) allows one to gather data about where and with whom individuals undertake their social activities. SNA therefore provides a way to study socially motivated leisure travel. This paper presents a data collection effort in the canton of Zürich, Switzerland, which combines a mobility survey with a name generator and interpreter to gather information about individuals’ egocentric social networks. A higher number of contacts leads to a higher response burden, which in turn increases item non-response. Subjects with low income and education generally name fewer contacts. With regards to travel behavior, the frequency of face-to-face meetings decreases sharply with distance to the residential location of contacts and face-to-face meetings are generally not substituted by other modes of communication (although increased usage of video chat is observed at long distances). Distance to social contacts is, therefore, an important factor in social leisure travel.
  • Risk based, multi objective vehicle routing problem for hazardous materials
    Item type: Conference Paper
    Cuneo, Valerio; Nigro, Marialisa; Carrese, Stefano; et al. (2018)
    Transportation Research Procedia
    The paper analyzes a practical case of study related to the distribution of fuels for the Total Erg Oil Company to the service stations located in the Province of Rome (Italy). The problem is formulated as a capacitated vehicle routing problem with time windows, where several heuristic procedures have been tested, considering both static and dynamic travel times. With respect to the standard operational costs used typically, a multivariable objective function has been proposed which takes into account also a new risk index. The risk index proposed is function of the population density of the zones covered by each path and of the estimated number of road accidents on each road link. In such a way, we take into account the population's exposure to the risk associated with an incidental event involving a fuel tank. The obtained output is the set of planned routes with minimum service cost and minimum risk. Results demonstrate how an accurate planning of the service saves up to 3 hours and 30 km on a daily basis compared to a benchmark. Moreover, the configuration of the service can be parameterized by the distribution company, by varying the weight adopted in order to include the risk index. Including the risk index may bring to a higher safety route planning, with an increase of the operating costs of only 2%.
  • Assessing the effect of route information on network observability applied to sensor location problems
    Item type: Conference Paper
    Rinaldi, Marco; Corman, Francesco; Viti, Francesco (2015)
    Transportation Research Procedia
    Link flow observability in traffic networks strongly relies on where sensors are installed. Full observability solutions are found by adopting various techniques exploiting existing relationships between links, which are determined either by using link-node relations, or by link-route relations. While the first relations are elegant as they do not require explicit route enumeration and therefore remain tractable for large-sized networks, they do not contain all the information at the route and OD levels. However, in case full route enumeration is not possible, route selection criteria are of paramount importance. In this paper we explore the impact of using k-shortest path algorithms for determining the route sets needed to solve the observability problems using link-route relations. In particular, we show how a limited amount of routes per OD pair is needed in order to incorporate all relevant information. Further, we demonstrate that selection route criteria that consider only linearly independent routes allows to find full observability solutions that need a lower number of sensors. Finally, we show that observability metrics, such as those presented in Viti et al. (2014), describe a direct relation between number of routes considered and degree of information. Through these metrics, we can show that link-route relations selected using only linearly independent links contains systematically more information. Moreover, there is empirical evidence that the marginal increment of information per additional route added decreases. This defines an asymptotic maximum value of information, which is found for a relatively limited amount of routes.
  • Reporting quality of travel and non-travel activities: A comparison of three different survey formats
    Item type: Conference Paper
    Aschauer, Florian; Hössinger, Reinhard; Schmid, Basil; et al. (2018)
    Transportation Research Procedia
    This paper reports a comparison of the Austrian National Household Travel Survey (HTS) and Time Use Survey (TUS) with a 3rd survey format – the "Mobility-Activity-Expenditure-Diary" – to better understand the specific strengths and weaknesses of HTS and TUS in terms of quantifying travel and non-travel activities and their specific underreporting effects. The main goal is to demonstrate how reliable we can infer from both survey types on travel and non-travel activities regarding different indicators.
  • A Multi-Agent System based on Unity 4 for virtual perception and wayfinding
    Item type: Conference Paper
    Becker-Asano, Christian; Ruzzoli, Felix; Hölscher, Christoph; et al. (2014)
    Transportation Research Procedia
  • Coordination of scheduling decisions in the management of airport airspace and taxiway operations
    Item type: Conference Paper
    Samà, Marcella; D'Ariano, Andrea; Corman, Francesco; et al. (2017)
    Transportation Research Procedia
    This paper addresses the real-time problem of coordinating aircraft ground and air operations in an airport area. At a congested airport, airborne decisions are related to take-off and landing operations, while ground (taxiway) decisions consist of scheduling aircraft movements between the gates and the runways. Since the runways are the initial/terminal points of both decisions, coordinated actions have a great potential to improve the overall performance. However, in the traffic control practice the different decisions are taken by different controllers, at least in large airports. Weak coordination may result in long queues at the runways, with increasing aircraft delays and energy consumption. This paper investigates models, methods and policies for improving the coordination between taxiway scheduling and airborne scheduling. The performance of a solution is measured in terms of delay and travel time, the latter being related to the energy consumption of an aircraft. A microscopic mathematical formulation is adopted to achieve reliable solutions. Exact and heuristic methods have been analysed in combination with the different policies, based on practical-size instances from Amsterdam Schiphol airport, in the Netherlands. Computational experience shows that good quality solutions can be found within limited time, compatible with real-time operations.
  • Multi-scale perimeter control approach in a connected-vehicle environment
    Item type: Journal Article
    Yang, Kaidi; Zheng, Nan; Menendez, Monica (2017)
    Transportation Research Procedia
    This paper proposes a novel approach to integrate optimal control of perimeter intersections (i.e. to minimize local delay) into the perimeter control scheme (i.e. to optimize traffic performance at the network level). This is a complex control problem rarely explored in the literature. In particular, modeling the interaction between the network level control and the local level control has not been fully considered. Utilizing the Macroscopic Fundamental Diagram (MFD) as the traffic performance indicator, we formulate a dynamic system model, and design a Model Predictive Control (MPC) based controller coupling two competing control objectives and optimizing the performance at the local and the network level as a whole. To solve this highly non-linear optimization problem, we employ an approximation framework, enabling the optimal solution of this large-scale problem to be feasible and efficient. Numerical analysis shows that by applying the proposed controller, the protected network can operate around the desired state as expressed by the MFD, while the total delay at the perimeter is minimized as well. Moreover, the paper sheds light on the robustness of the proposed controller. This multi-scale hybrid controller is further extended to a stochastic MPC scheme, where connected vehicles (CV) serve as the only data source. Hence, low penetration rates of CVs lead to strong noises in the controller. This is a first attempt to develop a network-level traffic control methodology by using the emerging CV technology. We consider the stochasticity in traffic state estimation and the shape of the MFD. Simulation analysis demonstrates the robustness of the proposed stochastic controller, showing that efficient controllers can indeed be designed with this newly-spread vehicle technology even in the absence of other data collection schemes (e.g. loop detectors).
Publications1 - 10 of 24