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Papers by Michael Florian
Modelling Public Transport Passenger Flows in the Era of Intelligent Transport Systems, 2016
This paper reports on the evaluation of alternative dynamic-equilibrium assignment methods for us... more This paper reports on the evaluation of alternative dynamic-equilibrium assignment methods for use in conjunction with traffic simulation models. Since the realism of a traffic simulation model results in an assignment map which is discontinuous and difficult to characterize analytically, algorithms for the static assignment problem are not directly applicable. The method of successive averages (MSA) has been applied to this problem (in the space of paths) and over the last few years has consistently performed well on a variety of real-world networks of considerable size. This paper evaluates two variants of this model inspired by gradient-based methods specifically, the projected gradient and reduced gradient and further tests these methods in conjunction with a dynamic step-size adjustment techinique. These path-based methods are compared with a recently developed splitting-rate model that is based on fundamental properties of traffic flow. The tests are executed on several congested urban networks of significant size (up to 6500 links) from North America and Europe. This paper reports on the evaluation of alternative dynamic-equilibrium assignment methods for use in conjunction with traffic simulation models. Since the realism of a traffic simulation model results in an assignment map which is discontinuous and difficult to characterize analytically, algorithms for the static assignment problem are not directly applicable. The method of successive averages (MSA) has been applied to this problem (in the space of paths) and over the last few years has consistently performed well on a variety of real-world networks of considerable size. This paper evaluates two variants of this model inspired by gradient-based methods specifically, the projected gradient and reduced gradient and further tests these methods in conjunction with a dynamic step-size adjustment techinique. These path-based methods are compared with a recently developed splitting-rate model that is based on fundamental properties of traffic flow. The tests are executed on several congested urban networks of significant size (up to 6500 links) from North America and Europe. For the covering abstract see ITRD E137145.
ABSTRACT This paper presents the first application of Dynameq to a freeway reconstruction impact ... more ABSTRACT This paper presents the first application of Dynameq to a freeway reconstruction impact study in the United States. Dynameq is a simulation-based equilibrium dynamic traffic assignment modeling software. The equilibrium solution property and the close to microscopic simulation traffic fidelity level make it an excellent tool in the traffic impact study. I-15 reconstruction project in Ontario, CA, involves mainline lane closure, ramp closure and freeway-to-freeway connector closure. The application model simulated the temporal effects of the closures on both freeways and arterials. The model development, calibration and reasonableness checking as well as the results from one of the construction scenarios, including the diversion routes and delays due to the construction, are presented in the paper.
ITSC 2001. 2001 IEEE Intelligent Transportation Systems. Proceedings (Cat. No.01TH8585)
ABSTRACT This paper investigates three methods for dynamic network loading that are considerably ... more ABSTRACT This paper investigates three methods for dynamic network loading that are considerably less detailed than microscopic modeling. Each of the three methods is based on a different approach to modeling traffic dynamics: link-based travel time functions, the cell-transmission model, and a link-based model derived from a simplified car-following relationship. A small test network was devised and the results from each model were compared to those obtained with a micro-simulator (INTEGRATION). Interpretation of the discrepancies observed in the results gives some indication of the relative importance of the different components of the three traffic models presented
European Journal of Operational Research, Sep 1, 2008
The evaluation of on-line intelligent transportation system (ITS) measures, such as adaptive rout... more The evaluation of on-line intelligent transportation system (ITS) measures, such as adaptive route-guidance and traffic management systems, depends heavily on the use of faster than real time traffic simulation models. Off-line applications, such as the testing of ITS ...
Dynamic Traffic Assignment (DTA) can be positioned between static assignment models and traffic m... more Dynamic Traffic Assignment (DTA) can be positioned between static assignment models and traffic micro-simulation models, both in terms of the level of modeling detail and also the appropriate network size. Compared to static models, simulation-based DTA models have a more realistic representation of traffic flow,and a more detailed representation of the transportation system. They are particularly useful when the level of congestion in the network or when the requirement for modeling more complex system components (e.g. adaptive control schemes, providing guidance information to drivers) make the application unsuitable for static assignment methodology. Simulation-based DTA models have proven to be fairly well-behaved in practice when used with correct input data, and they generally tend to converge to a stable solution that is within a reasonable distance (as measured by the relative gap) of true equilibrium. This paper examines various factors that have a significant impact on the convergence and stability of simulation-based DTA models. These factors include the size and complexity of the network, overall level of congestion, temporal discretization and stochastic effects. The paper presents some insights into these factors obtained through numerical experiments on actual networks, and also compares the performance of different assignment algorithms in the presence of these factors.
Transportmetrica A: Transport Science, 2020
A path-based algorithm is developed for the static traffic assignment problem (TAP). In each iter... more A path-based algorithm is developed for the static traffic assignment problem (TAP). In each iteration, it decomposes the problem into origin-destination (OD) pairs and solves each subproblem separately using the Wolfe reduced gradient (RG) method. This method reduces the dimensions of each single-OD subproblem by selecting a basic path between the OD pair and reformulating the subproblem in terms of the nonbasic paths. A column generation technique is included to avoid path enumeration in large scale networks. Also, some speed-up techniques are designed to improve the computational efficiency. The algorithm shifts flows from costlier paths to cheaper paths; however, the amount of flow shifted from a costlier path is proportional to not only the travel time but also the flow on the path. It is applied to the Philadelphia and Chicago test problems, while different strategies for choosing the basic paths are examined. The RG algorithm shows an excellent convergence to relative gaps of the order of 1.0E-14 when compared against several reference TAP algorithms.
European Transport Conference, 2007
This paper reports on the evaluation of alternative algorithms for dynamic, or time-varying, equi... more This paper reports on the evaluation of alternative algorithms for dynamic, or time-varying, equilibrium traffic assignment. The algorithms are used for pre-trip assignment, which reflects driver familiarity with expected traffic conditions, and are appropriate for off-...
Toll road operators and other toll facility stakeholders require analysis tools to estimate the r... more Toll road operators and other toll facility stakeholders require analysis tools to estimate the ridership and projected income for a variety of tolling schemes. Some tolling schemes commonly considered include distance-based tolls as well as derived schemes such as charging a maximum toll (or cap) for the use of the facility or minimum toll, if the distance based toll is less than this value. In addition, different entry ramp tolls are considered, which may be added to a distance-based toll and additionally subjected to the toll cap value. In order to meet these requirements a new model formulation and algorithm for distance-based toll modelling is developed. It uses the toll cost per link, which may be distance dependent, together with a minimum and maximum value of the tolls paid. The model is based on the addition of a set of temporary links to the network, which inherit the tolls and the delays of the original links. The method presented in this paper is general and self-contain...
Revue française d'informatique et de recherche opérationnelle. Série verte
Programmation hyperbolique en variables bivalentes Revue française d'automatique, d'informatique ... more Programmation hyperbolique en variables bivalentes Revue française d'automatique, d'informatique et de recherche opérationnelle. Recherche opérationnelle, tome 5, n o V1 (1971), p. 3-9. <http://www.numdam.org/item?id=RO_1971__5_1_3_0> © AFCET, 1971, tous droits réservés. L'accès aux archives de la revue « Revue française d'automatique, d'informatique et de recherche opérationnelle. Recherche opérationnelle » implique l'accord avec les conditions générales d'utilisation (http://www.numdam.org/ legal.php). Toute utilisation commerciale ou impression systématique est constitutive d'une infraction pénale. Toute copie ou impression de ce fichier doit contenir la présente mention de copyright. Article numérisé dans le cadre du programme Numérisation de documents anciens mathématiques http://www.numdam.org/ R.LR.O. (5 e année» V-l, 1971, p. 3-9) PROGRiU\IMATION HYPERBOLIQUE EN VARIABLES BIVALENTES par M. FLORIAN et P. ROBILLARD (*) (2) Résumé.-Plusieurs problèmes économiques peuvent être avantageusement formulés dans le contexte de la programmation hyperbolique pseudo-Booléenne à variables bivalentes. Dans cet article une approche nouvelle pour résoudre ces problèmes est décrite alors que Von montre que la solution optimale peut être obtenue après avoir résolu un nombre fini de problèmes qui consistent à minimiser une fonction linéaire sous les contraintes du problème original. Un algorithme est décrit et des résultats numériques concernant son utilisation sont discutés.
INFOR: Information Systems and Operational Research
1977 IEEE Conference on Decision and Control including the 16th Symposium on Adaptive Processes and A Special Symposium on Fuzzy Set Theory and Applications
Michael Florian Dgpartement d'informatique et de recherche operationnelle et Centre de r... more Michael Florian Dgpartement d'informatique et de recherche operationnelle et Centre de recherche sur les transports UniversitE de IbntrEal Case postale 6128, Succursale "A" Montreal (Quebec) H3C 337 ... We present a wthod for accelerating the convergence of the ...
Parallel Computing, 2001
We explore two types of parallel computing implementations for three algorithms for computing tem... more We explore two types of parallel computing implementations for three algorithms for computing temporal shortest paths on transportation networks. One implementation is done on a distributed network of SUN SPARC workstations using PVM and the other on a shared memory computing platform, a SUN SPARC server equipped with eight processors, using threads. Computational results obtained by using three networks originating from practice are presented. The shared memory computing platform is preferred for this application.
We consider a multi-class multi-mode variable demand network equilibrium model where the mode cho... more We consider a multi-class multi-mode variable demand network equilibrium model where the mode choice model is given by aggregate hierarchical logit structures and the destination choice is specified as a multi- proportional entropy type trip distribution model. The travel time of transit vehicles depends on the travel time of other vehicles using the road network. A variational inequality formulation captures
We consider the scheduling of n jobs on m identical machines when the jobs become available for p... more We consider the scheduling of n jobs on m identical machines when the jobs become available for processing at ready times a , , a, 2 0, require di time units for processing and must be completed by times bi for i = 1,2,. .. n. The objective chosen is that of minimizing the total elapsed time to complete all jobs subject to the ready time and due date constraints. preemption is not allowed. We present a multi-stage solution algorithm for this problem that is based on an implicit enumeration procedure and also uses the labelling type algorithm which solves the problem when preemption is allowed.
Modelling Public Transport Passenger Flows in the Era of Intelligent Transport Systems, 2016
This paper reports on the evaluation of alternative dynamic-equilibrium assignment methods for us... more This paper reports on the evaluation of alternative dynamic-equilibrium assignment methods for use in conjunction with traffic simulation models. Since the realism of a traffic simulation model results in an assignment map which is discontinuous and difficult to characterize analytically, algorithms for the static assignment problem are not directly applicable. The method of successive averages (MSA) has been applied to this problem (in the space of paths) and over the last few years has consistently performed well on a variety of real-world networks of considerable size. This paper evaluates two variants of this model inspired by gradient-based methods specifically, the projected gradient and reduced gradient and further tests these methods in conjunction with a dynamic step-size adjustment techinique. These path-based methods are compared with a recently developed splitting-rate model that is based on fundamental properties of traffic flow. The tests are executed on several congested urban networks of significant size (up to 6500 links) from North America and Europe. This paper reports on the evaluation of alternative dynamic-equilibrium assignment methods for use in conjunction with traffic simulation models. Since the realism of a traffic simulation model results in an assignment map which is discontinuous and difficult to characterize analytically, algorithms for the static assignment problem are not directly applicable. The method of successive averages (MSA) has been applied to this problem (in the space of paths) and over the last few years has consistently performed well on a variety of real-world networks of considerable size. This paper evaluates two variants of this model inspired by gradient-based methods specifically, the projected gradient and reduced gradient and further tests these methods in conjunction with a dynamic step-size adjustment techinique. These path-based methods are compared with a recently developed splitting-rate model that is based on fundamental properties of traffic flow. The tests are executed on several congested urban networks of significant size (up to 6500 links) from North America and Europe. For the covering abstract see ITRD E137145.
ABSTRACT This paper presents the first application of Dynameq to a freeway reconstruction impact ... more ABSTRACT This paper presents the first application of Dynameq to a freeway reconstruction impact study in the United States. Dynameq is a simulation-based equilibrium dynamic traffic assignment modeling software. The equilibrium solution property and the close to microscopic simulation traffic fidelity level make it an excellent tool in the traffic impact study. I-15 reconstruction project in Ontario, CA, involves mainline lane closure, ramp closure and freeway-to-freeway connector closure. The application model simulated the temporal effects of the closures on both freeways and arterials. The model development, calibration and reasonableness checking as well as the results from one of the construction scenarios, including the diversion routes and delays due to the construction, are presented in the paper.
ITSC 2001. 2001 IEEE Intelligent Transportation Systems. Proceedings (Cat. No.01TH8585)
ABSTRACT This paper investigates three methods for dynamic network loading that are considerably ... more ABSTRACT This paper investigates three methods for dynamic network loading that are considerably less detailed than microscopic modeling. Each of the three methods is based on a different approach to modeling traffic dynamics: link-based travel time functions, the cell-transmission model, and a link-based model derived from a simplified car-following relationship. A small test network was devised and the results from each model were compared to those obtained with a micro-simulator (INTEGRATION). Interpretation of the discrepancies observed in the results gives some indication of the relative importance of the different components of the three traffic models presented
European Journal of Operational Research, Sep 1, 2008
The evaluation of on-line intelligent transportation system (ITS) measures, such as adaptive rout... more The evaluation of on-line intelligent transportation system (ITS) measures, such as adaptive route-guidance and traffic management systems, depends heavily on the use of faster than real time traffic simulation models. Off-line applications, such as the testing of ITS ...
Dynamic Traffic Assignment (DTA) can be positioned between static assignment models and traffic m... more Dynamic Traffic Assignment (DTA) can be positioned between static assignment models and traffic micro-simulation models, both in terms of the level of modeling detail and also the appropriate network size. Compared to static models, simulation-based DTA models have a more realistic representation of traffic flow,and a more detailed representation of the transportation system. They are particularly useful when the level of congestion in the network or when the requirement for modeling more complex system components (e.g. adaptive control schemes, providing guidance information to drivers) make the application unsuitable for static assignment methodology. Simulation-based DTA models have proven to be fairly well-behaved in practice when used with correct input data, and they generally tend to converge to a stable solution that is within a reasonable distance (as measured by the relative gap) of true equilibrium. This paper examines various factors that have a significant impact on the convergence and stability of simulation-based DTA models. These factors include the size and complexity of the network, overall level of congestion, temporal discretization and stochastic effects. The paper presents some insights into these factors obtained through numerical experiments on actual networks, and also compares the performance of different assignment algorithms in the presence of these factors.
Transportmetrica A: Transport Science, 2020
A path-based algorithm is developed for the static traffic assignment problem (TAP). In each iter... more A path-based algorithm is developed for the static traffic assignment problem (TAP). In each iteration, it decomposes the problem into origin-destination (OD) pairs and solves each subproblem separately using the Wolfe reduced gradient (RG) method. This method reduces the dimensions of each single-OD subproblem by selecting a basic path between the OD pair and reformulating the subproblem in terms of the nonbasic paths. A column generation technique is included to avoid path enumeration in large scale networks. Also, some speed-up techniques are designed to improve the computational efficiency. The algorithm shifts flows from costlier paths to cheaper paths; however, the amount of flow shifted from a costlier path is proportional to not only the travel time but also the flow on the path. It is applied to the Philadelphia and Chicago test problems, while different strategies for choosing the basic paths are examined. The RG algorithm shows an excellent convergence to relative gaps of the order of 1.0E-14 when compared against several reference TAP algorithms.
European Transport Conference, 2007
This paper reports on the evaluation of alternative algorithms for dynamic, or time-varying, equi... more This paper reports on the evaluation of alternative algorithms for dynamic, or time-varying, equilibrium traffic assignment. The algorithms are used for pre-trip assignment, which reflects driver familiarity with expected traffic conditions, and are appropriate for off-...
Toll road operators and other toll facility stakeholders require analysis tools to estimate the r... more Toll road operators and other toll facility stakeholders require analysis tools to estimate the ridership and projected income for a variety of tolling schemes. Some tolling schemes commonly considered include distance-based tolls as well as derived schemes such as charging a maximum toll (or cap) for the use of the facility or minimum toll, if the distance based toll is less than this value. In addition, different entry ramp tolls are considered, which may be added to a distance-based toll and additionally subjected to the toll cap value. In order to meet these requirements a new model formulation and algorithm for distance-based toll modelling is developed. It uses the toll cost per link, which may be distance dependent, together with a minimum and maximum value of the tolls paid. The model is based on the addition of a set of temporary links to the network, which inherit the tolls and the delays of the original links. The method presented in this paper is general and self-contain...
Revue française d'informatique et de recherche opérationnelle. Série verte
Programmation hyperbolique en variables bivalentes Revue française d'automatique, d'informatique ... more Programmation hyperbolique en variables bivalentes Revue française d'automatique, d'informatique et de recherche opérationnelle. Recherche opérationnelle, tome 5, n o V1 (1971), p. 3-9. <http://www.numdam.org/item?id=RO_1971__5_1_3_0> © AFCET, 1971, tous droits réservés. L'accès aux archives de la revue « Revue française d'automatique, d'informatique et de recherche opérationnelle. Recherche opérationnelle » implique l'accord avec les conditions générales d'utilisation (http://www.numdam.org/ legal.php). Toute utilisation commerciale ou impression systématique est constitutive d'une infraction pénale. Toute copie ou impression de ce fichier doit contenir la présente mention de copyright. Article numérisé dans le cadre du programme Numérisation de documents anciens mathématiques http://www.numdam.org/ R.LR.O. (5 e année» V-l, 1971, p. 3-9) PROGRiU\IMATION HYPERBOLIQUE EN VARIABLES BIVALENTES par M. FLORIAN et P. ROBILLARD (*) (2) Résumé.-Plusieurs problèmes économiques peuvent être avantageusement formulés dans le contexte de la programmation hyperbolique pseudo-Booléenne à variables bivalentes. Dans cet article une approche nouvelle pour résoudre ces problèmes est décrite alors que Von montre que la solution optimale peut être obtenue après avoir résolu un nombre fini de problèmes qui consistent à minimiser une fonction linéaire sous les contraintes du problème original. Un algorithme est décrit et des résultats numériques concernant son utilisation sont discutés.
INFOR: Information Systems and Operational Research
1977 IEEE Conference on Decision and Control including the 16th Symposium on Adaptive Processes and A Special Symposium on Fuzzy Set Theory and Applications
Michael Florian Dgpartement d'informatique et de recherche operationnelle et Centre de r... more Michael Florian Dgpartement d'informatique et de recherche operationnelle et Centre de recherche sur les transports UniversitE de IbntrEal Case postale 6128, Succursale "A" Montreal (Quebec) H3C 337 ... We present a wthod for accelerating the convergence of the ...
Parallel Computing, 2001
We explore two types of parallel computing implementations for three algorithms for computing tem... more We explore two types of parallel computing implementations for three algorithms for computing temporal shortest paths on transportation networks. One implementation is done on a distributed network of SUN SPARC workstations using PVM and the other on a shared memory computing platform, a SUN SPARC server equipped with eight processors, using threads. Computational results obtained by using three networks originating from practice are presented. The shared memory computing platform is preferred for this application.
We consider a multi-class multi-mode variable demand network equilibrium model where the mode cho... more We consider a multi-class multi-mode variable demand network equilibrium model where the mode choice model is given by aggregate hierarchical logit structures and the destination choice is specified as a multi- proportional entropy type trip distribution model. The travel time of transit vehicles depends on the travel time of other vehicles using the road network. A variational inequality formulation captures
We consider the scheduling of n jobs on m identical machines when the jobs become available for p... more We consider the scheduling of n jobs on m identical machines when the jobs become available for processing at ready times a , , a, 2 0, require di time units for processing and must be completed by times bi for i = 1,2,. .. n. The objective chosen is that of minimizing the total elapsed time to complete all jobs subject to the ready time and due date constraints. preemption is not allowed. We present a multi-stage solution algorithm for this problem that is based on an implicit enumeration procedure and also uses the labelling type algorithm which solves the problem when preemption is allowed.