A Review of Dynamic Traffic Assignment Computer Packages
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paper_title: Computing dynamic user equilibria for large-scale transportation networks

paper_content:

In this paper, we present an approach for determining dynamic user equilibria. The method is suitable for disaggregated microscopic and mesoscopic simulation-based models. It is a modification of the convex-simplex method, which disposes with the line search step, and controls the subset of travelers to be re-routed at each step while updating the link travel times after each assignment. To guarantee finite termination, a suitable stopping criterion is adopted. The proposed method is implemented within TRANSIMS, the Transportation Analysis and Simulation System, as a two-stage process that employs a combined use of link performance functions and a microsimulator in order to design a framework suitable for application to real transportation systems. To demonstrate this capability, we apply the developed methodology to a large-scale network, Bignet, which is part of the transportation city network of Portland, Oregon; and a medium-scale network, Blacksburg, Virginia; and provide some comparative analyses. Our results exhibit that an improved distribution of travelers is obtained while consuming less than 17–33% of the effort required by the current version of TRANSIMS.
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paper_title: Foundations of Dynamic Traffic Assignment: The Past, the Present and the Future

paper_content:

Dynamic Traffic Assignment (DTA) has evolved substantially since the pioneering work of Merchant and Nemhauser. Numerous formulations and solutions approaches have been introduced ranging from mathematical programming, to variational inequality, optimal control, and simulation-based. The aim of this special issue is to document the main existing DTA approaches for future reference. This opening paper will summarize the current understanding of DTA, review the existing literature, make the connection to the approaches presented in this special issue, and attempt to hypothesize about the future.
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paper_title: Foundations of Dynamic Traffic Assignment: The Past, the Present and the Future

paper_content:

Dynamic Traffic Assignment (DTA) has evolved substantially since the pioneering work of Merchant and Nemhauser. Numerous formulations and solutions approaches have been introduced ranging from mathematical programming, to variational inequality, optimal control, and simulation-based. The aim of this special issue is to document the main existing DTA approaches for future reference. This opening paper will summarize the current understanding of DTA, review the existing literature, make the connection to the approaches presented in this special issue, and attempt to hypothesize about the future.
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paper_title: CREATING SYNTHETIC BASELINE POPULATIONS

paper_content:

To develop activity-based travel models using microsimulation, individual travelers and households must be considered. Methods for creating baseline synthetic populations of households and persons using 1990 census data are given. Summary tables from the Census Bureau STF-3A are used in conjunction with the Public Use Microdata Sample (PUMS), and Iterative Proportional Fitting (IPF) is applied to estimate the proportion of households in a block group or census tract with a desired combination of demographics. Households are generated by selection of households from the associated PUMS according to these proportions. The tables of demographic proportions which are exploited here to make household selections from the PUMS may be used in traditional modeling. The procedures are validated by creating pseudo census tracts from PUMS samples and considering the joint distribution of the size of households and the number of vehicles in the households. It is shown that the joint distributions created by these methods do not differ substantially from the true values. Additionally the effects of small changes in the procedure, such as imputation of additional demographics and adding partial counts to the constructed demographic tables are discussed in the paper.
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paper_title: Formal language constrained path problems

paper_content:

Given an alphabet σ, a (directed) graph G whose edges are weighted and σ-labeled, and a formal language L \(\subseteq\) σ*, we consider the problem of finding a shortest (simple) path p in G complying with the additional constraint that l(p) ∃ L. Here l(p) denotes the unique word given by concatenating the σ-labels in G along the path p.
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paper_title: Computing dynamic user equilibria for large-scale transportation networks

paper_content:

In this paper, we present an approach for determining dynamic user equilibria. The method is suitable for disaggregated microscopic and mesoscopic simulation-based models. It is a modification of the convex-simplex method, which disposes with the line search step, and controls the subset of travelers to be re-routed at each step while updating the link travel times after each assignment. To guarantee finite termination, a suitable stopping criterion is adopted. The proposed method is implemented within TRANSIMS, the Transportation Analysis and Simulation System, as a two-stage process that employs a combined use of link performance functions and a microsimulator in order to design a framework suitable for application to real transportation systems. To demonstrate this capability, we apply the developed methodology to a large-scale network, Bignet, which is part of the transportation city network of Portland, Oregon; and a medium-scale network, Blacksburg, Virginia; and provide some comparative analyses. Our results exhibit that an improved distribution of travelers is obtained while consuming less than 17–33% of the effort required by the current version of TRANSIMS.
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paper_title: Urban Transportation Networks: Equilibrium Analysis with Mathematical Programming Methods

paper_content:

Pharmaceutical compositions useful for effecting diuresis and saluresis and for treating hypertension in humans and animals are produced by combining a pyrazol-5-one of the formula: or a pharmaceutically acceptable nontoxic salt thereof wherein R is hydrogen, lower alkyl or amino; X is methylene, ethylene, methylene wherein 1 hydrogen at
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paper_title: The dynamics of iterated transportation simulations

paper_content:

Iterating between a router and a traffic micro-simulation is an increasibly accepted method for doing traffic assignment. This paper, after pointing out that the analytical theory of simulation-based assignment to-date is insufficient for some practical cases, presents results of simulation studies from a real world study. Specifically, we look into the issues of uniqueness, variability, and robustness and validation. Regarding uniqueness, despite some cautionary notes from a theoretical point of view, we find no indication of ``meta-stable'' states for the iterations. Variability however is considerable. By variability we mean the variation of the simulation of a given plan set by just changing the random seed. We show then results from three different micro-simulations under the same iteration scenario in order to test for the robustness of the results under different implementations. We find the results encouraging, also when comparing to reality and with a traditional assignment result.
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paper_title: On the equivalence between some shortest path algorithms

paper_content:

In this paper, we show the equivalence between a particular implementation of the Partitioned Shortest Path (PSP) algorithm, Moore's algorithm, and a dynamic programming approach with an appropriate state space and decision space reduction, when applied to a problem of determining a shortest simple path from a given node to all the nodes in a network having arbitrary costs but with no negative cost circuits. This equivalence provides insights into the PSP method, shows that Moore's algorithm has a polynomial-time implementation, and facilitates by definition the proofs of various properties.
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paper_title: The CONTRAM Dynamic Traffic Assignment Model

paper_content:

CONTRAM is a computer model of time-varying traffic in road networks, which takes as input the network definition and time-varying demand for travel between a set of origin and destination zones, and outputs the resulting network flows, routes and travel times. It combines a macroscopic time-sliced traffic model with disaggregate dynamic assignment of traffic, so is intermediate between macroscopic equilibrium and microscopic models. The paper details the methods used, including time-dependent queuing which plays a central role, and the treatment of network definition, user classes, road capacities, signals and coordination, vehicle emissions, Intelligent Transport Systems and research lines.
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paper_title: CONTRAM: A TRAFFIC ASSIGNMENT MODEL FOR PREDICTING FLOWS AND QUEUES DURING PEAK PERIODS

paper_content:

The report describes a computer-based traffic assignment and queueing model for use in the design of urban traffic management schemes. The model is called CONTRAM--CONtinuous TRaffic Assignment Model. CONTRAM requires data on time-varying flow demands (for example as occur in a "peak period"), and predicts the flows, delays and queues throughout a network of roads and junctions. The movement of traffic is modelled by grouping vehicles together to form "packets". Each packet is assigned to its minimum journey time route through the network, taking into account delays and queues at junctions. The report is divided into three parts. The first outlines the assumptions and structure of the model. The development of the model, sensitivity tests and validation work are described in the second part and examples to illustrate applications of the model are described in the third part. /Author/
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paper_title: Network state estimation and prediction for real-time traffic management

paper_content:

Advanced Traveler Information Systems (ATIS) and Advanced Traffic Management Systems (ATMS) have the potential to contribute to the solution of the traffic congestion problem. DynaMIT is a real-time system that can be used to generate guidance for travelers. The main principle on which DynaMIT is based is that information should be consistent, and user optimal. Consistency implies that the traffic conditions experienced by the travelers are consistent with the condition assumed in generating the guidance. To generate consistent user optimal information, DynaMIT performs two main functions: state estimation and prediction. A demand simulator and a supply simulator interact to perform these tasks. A case study demonstrates the value of the system.
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paper_title: System optimal and user equilibrium time-dependent traffic assignment in congested networks

paper_content:

This paper formulates two dynamic network traffic assignment models in which O-D desires for the planning horizon are assumed known a priori: the system optimal (SO) and the user equilibrium (UE) time-dependent traffic assignment formulations. Solution algorithms developed and implemented for these models incorporate a traffic simulation model within an overall iterative search framework. Experiments conducted on a test network provide the basis for a comparative analysis of system performance under the SO and UE models.
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Title: A Review of Dynamic Traffic Assignment Computer Packages

Section 1: INTRODUCTION
Description 1: This section introduces traffic assignment, its approaches, classifications, and importance of dynamic traffic assignment (DTA) models.

Section 2: DEMAND ESTIMATION AND PREDICTION
Description 2: This section discusses the challenges and methodologies of estimating and predicting time-dependent origin-destination demand matrices within DTA models.

Section 3: TRANSPORTATION SUPPLY AND OUTPUT
Description 3: This section covers transportation network characteristics, detailing how different models represent network nodes, links, and associated traffic control systems.

Section 4: TRANSIMS' Traffic Assignment Model
Description 4: This section provides an in-depth explanation of the TRANSIMS dynamic traffic assignment model, including its Route Planner, Microsimulator, and Feedback modules.

Section 5: CONTRAM's Traffic Assignment Model
Description 5: This section describes the dynamic user equilibrium procedure in CONTRAM, focusing on its time-sliced demand division, routing, and iterative re-assignment.

Section 6: DynaMIT-P's Traffic Assignment Model
Description 6: This section reviews the supply and demand simulators in DynaMIT-P and explains its iterative interaction process to achieve equilibrium solutions.

Section 7: DYNASMART-P's Traffic Assignment Model
Description 7: This section details the heuristic simulation-based iterative procedure used in DYNASMART-P to solve dynamic user equilibrium and system optimal problems.

Section 8: PARAMICS's Traffic Assignment Model
Description 8: This section outlines the decision-making processes for drivers in PARAMICS and its supported assignment methods including all-or-nothing, stochastic, and dynamic feedback.

Section 9: VISSIM's Traffic Assignment Model
Description 9: This section describes VISSIM's approach to dynamic traffic assignment, including its vehicle and driver behavior models, and iterative simulation runs.

Section 10: SUMMARY AND CONCLUSION
Description 10: This section summarizes the paper, highlighting the importance and challenges of DTA, and contrasts the reviewed packages with TRANSIMS, identifying areas for future research and improvement.