Malachy Carey - Academia.edu (original) (raw)
Papers by Malachy Carey
New Developments in Transport Planning, 2010
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Transportation Science, 2014
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Operations Research, Feb 1, 1987
Page 1. OPTIMAL TIME-VARYING FLOWS ON CONGESTED NETWORKS MALACHY CAREY Carnegie-Mellon University... more Page 1. OPTIMAL TIME-VARYING FLOWS ON CONGESTED NETWORKS MALACHY CAREY Carnegie-Mellon University, Pittsburgh, Pennsylvania (Received August 1982; revisions received September 1983, December 1984, February 1986; accepted March 1986) ...
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Transportation Research Part B Methodological, 2002
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The Journal of the Operational Research Society, Aug 1, 1995
We set out a model, algorithms and strategies for the train pathing and timetabling problem for r... more We set out a model, algorithms and strategies for the train pathing and timetabling problem for rail lines of the type normally found in Britain and Europe; that is, lines having separate tracks for trains in each direction. As the pathing problem is combinatorially difficult we propose ...
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Econometrica, 1977
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Transportation Research Part B Methodological, Nov 1, 2003
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ABSTRACT
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Transportation Research Part B: Methodological, 2007
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Transportation Research Part B: Methodological, 2007
ABSTRACT Many countries have busy rail networks with highly complex patterns of train services th... more ABSTRACT Many countries have busy rail networks with highly complex patterns of train services that require careful scheduling to fit these to the existing infrastructure, while avoiding conflicts between large numbers of trains moving at different speeds within and between multi-platform stations on conflicting lines, while satisfying other constraints and objectives. However, the construction and coordination of train schedules and plans for many rail networks is a rather slow process in which conflicts of proposed train times, lines and platforms are found and resolved 'by hand'. Even for a medium size rail network, this requires a large numbers of train schedulers or planners many months to complete, and makes it difficult or impossible to explore alternative schedules, plans, operating rules, objectives, etc. As a contribution towards more automated methods, we have developed heuristic algorithms to assist in the task of finding and resolving the conflicts in draft train schedules. We start from algorithms that schedule trains at a single train station, and extend these to handle a series of complex stations linked by multiple one-way lines in each direction, traversed by trains of differing types and speeds. To test the algorithms we applied them to scheduling trains for a busy system of 25 interconnected stations, with each station having up to 30 sub-platforms and several hundred train movements per day. We here report on the results from many hundreds of test runs. To make the tests more challenging, the algorithms start from initial draft timetables that we constructed so as to contain very large numbers of conflicts to be resolved. The algorithms, implemented in C code and run on a Pentium PC, found and resolved all conflicts very quickly. A further purpose of the algorithms is that they can be used to simulate and explore the effects of alternative draft timetable, operating policies, station layouts, and random delays or failures.
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Transportation Research Part A: Policy and Practice, 2003
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Transportation Research Part B: Methodological, 1985
... 1. The horizontally and vertically shaded areas represent the first and second integral terms... more ... 1. The horizontally and vertically shaded areas represent the first and second integral terms, respectively, in D. It is easy to see that if p and c are chosen so as to 234 0 M. CAREY Fig. 1(a). B 0 A Fig. ... An example is the algorithm of LeBlanc et al. ...
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Transportation Research Part B: Methodological, 1992
... small number of optimization models have been developed to date to handle dynamic traffic ass... more ... small number of optimization models have been developed to date to handle dynamic traffic assignment on networks (eg see Carey, 1986, 1987; Carey and Srinivasan, 1988; Friesz, Luque, Tobin, and Wie, 1988; Merchant, 1974; Merchant and Nemhauser, 1978a; Powell, 1991 ...
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Transportation Research Part B: Methodological, 2011
ABSTRACT A dynamic traffic assignment (DTA) model typically consists of a traffic performance mod... more ABSTRACT A dynamic traffic assignment (DTA) model typically consists of a traffic performance model and a route choice model. The traffic performance model describes how traffic propagates (over time) along routes connecting origin-destination (OD) pairs, examples being the cell transmission model, the vertical queueing model and the travel time model. This is implemented in a dynamic network loading (DNL) algorithm, which uses the given route inflows to compute the link inflows (and hence link costs), which are then used to compute the route travel times (and hence route costs). A route swap process specifies the route inflows for tomorrow (at the next iteration) based on the route inflows today (at the current iteration). A dynamic user equilibrium (DUE), where each traveller on the network cannot reduce his or her cost of travel by switching to another route, can be sought by iterating between the DNL algorithm and the route swap process. The route swap process itself takes up very little computational time (although route set generation can be very computationally intensive for large networks). However, the choice of route swap process dramatically affects convergence and the speed of convergence. The paper details several route swap processes and considers whether they lead to a convergent system, assuming that the route cost vector is a monotone function of the route inflow vector.
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New Developments in Transport Planning, 2010
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Transportation Science, 2014
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Operations Research, Feb 1, 1987
Page 1. OPTIMAL TIME-VARYING FLOWS ON CONGESTED NETWORKS MALACHY CAREY Carnegie-Mellon University... more Page 1. OPTIMAL TIME-VARYING FLOWS ON CONGESTED NETWORKS MALACHY CAREY Carnegie-Mellon University, Pittsburgh, Pennsylvania (Received August 1982; revisions received September 1983, December 1984, February 1986; accepted March 1986) ...
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Transportation Research Part B Methodological, 2002
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The Journal of the Operational Research Society, Aug 1, 1995
We set out a model, algorithms and strategies for the train pathing and timetabling problem for r... more We set out a model, algorithms and strategies for the train pathing and timetabling problem for rail lines of the type normally found in Britain and Europe; that is, lines having separate tracks for trains in each direction. As the pathing problem is combinatorially difficult we propose ...
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Econometrica, 1977
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Transportation Research Part B Methodological, Nov 1, 2003
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ABSTRACT
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Transportation Research Part B: Methodological, 2007
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Transportation Research Part B: Methodological, 2007
ABSTRACT Many countries have busy rail networks with highly complex patterns of train services th... more ABSTRACT Many countries have busy rail networks with highly complex patterns of train services that require careful scheduling to fit these to the existing infrastructure, while avoiding conflicts between large numbers of trains moving at different speeds within and between multi-platform stations on conflicting lines, while satisfying other constraints and objectives. However, the construction and coordination of train schedules and plans for many rail networks is a rather slow process in which conflicts of proposed train times, lines and platforms are found and resolved 'by hand'. Even for a medium size rail network, this requires a large numbers of train schedulers or planners many months to complete, and makes it difficult or impossible to explore alternative schedules, plans, operating rules, objectives, etc. As a contribution towards more automated methods, we have developed heuristic algorithms to assist in the task of finding and resolving the conflicts in draft train schedules. We start from algorithms that schedule trains at a single train station, and extend these to handle a series of complex stations linked by multiple one-way lines in each direction, traversed by trains of differing types and speeds. To test the algorithms we applied them to scheduling trains for a busy system of 25 interconnected stations, with each station having up to 30 sub-platforms and several hundred train movements per day. We here report on the results from many hundreds of test runs. To make the tests more challenging, the algorithms start from initial draft timetables that we constructed so as to contain very large numbers of conflicts to be resolved. The algorithms, implemented in C code and run on a Pentium PC, found and resolved all conflicts very quickly. A further purpose of the algorithms is that they can be used to simulate and explore the effects of alternative draft timetable, operating policies, station layouts, and random delays or failures.
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Transportation Research Part A: Policy and Practice, 2003
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Transportation Research Part B: Methodological, 1985
... 1. The horizontally and vertically shaded areas represent the first and second integral terms... more ... 1. The horizontally and vertically shaded areas represent the first and second integral terms, respectively, in D. It is easy to see that if p and c are chosen so as to 234 0 M. CAREY Fig. 1(a). B 0 A Fig. ... An example is the algorithm of LeBlanc et al. ...
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Transportation Research Part B: Methodological, 1992
... small number of optimization models have been developed to date to handle dynamic traffic ass... more ... small number of optimization models have been developed to date to handle dynamic traffic assignment on networks (eg see Carey, 1986, 1987; Carey and Srinivasan, 1988; Friesz, Luque, Tobin, and Wie, 1988; Merchant, 1974; Merchant and Nemhauser, 1978a; Powell, 1991 ...
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Transportation Research Part B: Methodological, 2011
ABSTRACT A dynamic traffic assignment (DTA) model typically consists of a traffic performance mod... more ABSTRACT A dynamic traffic assignment (DTA) model typically consists of a traffic performance model and a route choice model. The traffic performance model describes how traffic propagates (over time) along routes connecting origin-destination (OD) pairs, examples being the cell transmission model, the vertical queueing model and the travel time model. This is implemented in a dynamic network loading (DNL) algorithm, which uses the given route inflows to compute the link inflows (and hence link costs), which are then used to compute the route travel times (and hence route costs). A route swap process specifies the route inflows for tomorrow (at the next iteration) based on the route inflows today (at the current iteration). A dynamic user equilibrium (DUE), where each traveller on the network cannot reduce his or her cost of travel by switching to another route, can be sought by iterating between the DNL algorithm and the route swap process. The route swap process itself takes up very little computational time (although route set generation can be very computationally intensive for large networks). However, the choice of route swap process dramatically affects convergence and the speed of convergence. The paper details several route swap processes and considers whether they lead to a convergent system, assuming that the route cost vector is a monotone function of the route inflow vector.
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