Browsing by Author "Bell, Michael G. H."

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Investigating transport network vulnerability by capacity weighted spectral analysis
(2017-05-01)
Bell, Michael G. H.
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Kurauchi, Fumitaka
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Perera, Supun
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Wong, Walter
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運輸與物流管理系註：原交通所+運管所
Transport networks operating at or near capacity are vulnerable to disruptions, so flow bottlenecks are potent sources of vulnerability. This paper presents an efficient method for finding transport network cuts, which may constitute such bottlenecks. Methods for assessing network vulnerability found in the literature require origin-destination demands and path assignment. However, in transport network planning and design, demand information is often missing, out of date, partial or inaccurate. Capacity weighted spectral partitioning is proposed to identify potential flow bottlenecks in the network, without reference to demand information or path assignments. This method identifies the network cut with least capacity, taking into account the relative sizes of the sub-networks either side of the cut. Spectral analysis has the added advantage of tractability, even for large networks, as shown by numerical examples for a five-node illustrative example, the Sioux Falls road network and the Gifu Prefecture road network. (C) 2017 Elsevier Ltd. All rights reserved.
The optimal dispatching of taxis under congestion: a rolling horizon approach
(2006-03-01)
Wong, K. I.
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Bell, Michael G. H.
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運輸與物流管理系註：原交通所+運管所
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Department of Transportation and Logistics Management
Taxis make an important contribution to transport in many parts of the world, offering demand-responsive, door-to-door transport. In larger cities, taxis may be hailed on-street or taken from taxi ranks. Elsewhere, taxis are usually ordered by phone. The objective of a taxi dispatcher is to maximize the efficiency of fleet utilization. While the spatial and temporal distribution of taxi requests has in general a high degree of predictability, real time traffic congestion information can be collected and disseminated to taxis by communication technologies. The efficiency of taxi dispatching may be significantly improved through the anticipation of future requests and traffic conditions. A rolling horizon approach to the optimisation of taxi dispatching is formulated, which takes the stochastic and dynamic nature of the problem into account. Numerical experiments are presented to illustrate the performances of the heuristics, taking the time dependency of travel times and passenger arrivals into account.