Modeling

Urban Gridlock: Macroscopic Modeling and Mitigation Approaches

Daganzo, Carlos F.
2007

This paper describes an adaptive control approach to improve urban mobility and relieve congestion. The basic idea consists in monitoring and controlling aggregate vehicular accumulations at the neighborhood level. To do this, physical models of the gridlock phenomenon are presented both for single neighborhoods and for systems of inter-connected neighborhoods. The models are dynamic, aggregate and only require observable inputs. The latter can be obtained in real-time if the neighborhoods are properly instrumented. Therefore, the models can be used for adaptive control. Experiments should...

City-Scale Transport Modeling: An Approach for Nairobi, Kenya

Daganzo, C. F.
Li, Yuwei
Gonzales, Eric J.
Geroliminis, Nikolas
2007

Traffic congestion poses problems for cities around the world, especially in rapidly growing and motorizing cities like Nairobi, Kenya. We show here how we plan to use in the context of Nairobi a new theory that relates the mobility provided by a city’s street network to the number of vehicles on the network (including private cars and public transport) and to key aggregate descriptors of both the street infrastructure and the public transport services. Conventional micro-simulation models require vast quantities of data and produce unreliable detailed results. The new theory asserts that...

The Potential of Parsimonious Models for Understanding Large Scale Transportation Systems and Answering Big Picture Questions

Daganzo, Carlos F.
Gayah, Vikash V.
Gonzales, Eric J.
2012

A model with few variables is said to be parsimonious. If it is also analytically tractable, physically realistic, and conceptually insightful, it is said to be effective. Effective parsimonious models have long been used in fields such as economics and applied physics to describe the aggregate behavior of systems as opposed to the behavior of their individual parts. In transportation, these models are particularly well suited to address big picture questions because they provide insights that might be lost when focusing on details. This paper presents an abbreviated history of effective...

Jitney-lite: a Flexible-Route Feeder Service for Developing Countries

Sangveraphunsiri, Tawit
Cassidy, Michael J.
Daganzo, Carlos F.
2022

The paper develops a novel strategy for delivering feeder service in support of trunk-line transit. The strategy is well suited to developing countries, where costs of emergent communication technologies often preclude their use. The strategy, termed Jitney-lite, is a form of collective transportation that provides a degree of flexibility. Patrons who board an outbound Jitney-lite vehicle at a transit station are delivered to their doorsteps. On the return trip to the station, the vehicle boards new patrons in the manner of traditional, fixed-route, fixed-stop feeder-bus service. Continuum...

Bi-Level Optimization Model for DTA Flow and Speed Calibration

Samaei, Maryam
Ameli, Mostafa
Davis, Jon F.
McQuade, Sean T.
Bayen, Alexandre M.
2024

Dynamic traffic assignment (DTA) models are capable of capturing traffic dynamics and are well-known as a critical tool in controlling and predicting the traffic situation Ameli (2019). DTA simulation allows us to measure the results of deploying different technologies and applying different policies along with real experiments Ameli et al. (2020); Chen et al. (2021); Balzer et al. (2023). One of the crucial steps to achieve realistic results from simulation tools is calibration. It aims to determine the DTA model’s input such that the output represents traffic scenarios with a reliable...

Eulerian Trilogy

Sun, Dengfeng
Yang, Samuel
Bayen, Alexandre M.
2012

Mixed Initial-Boundary Value Problems for Scalar Conservation Laws: Application to the Modeling of Transportation Networks

Strub, Issam S.
Bayen, Alexandre M.
Hespanha, João P.
Tiwari, Ashish
2006

This article proves the existence and uniqueness of a weak solution to a scalar conservation law on a bounded domain. A weak formulation of hybrid boundary conditions is needed for the problem to be well posed. The boundary conditions are represented by a hybrid automaton with switches between the modes determined by the direction of characteristics of the system at the boundary. The existence of the solution results from the convergence of a Godunov scheme derived in this article. This weak formulation is written explicitly in the context of a strictly concave flux function (relevant for...

Sensing by Proxy: Occupancy Detection Based on Indoor CO2 Concentration

Jin, Ming
Bekiaris-Liberis, Nikolaos
Weekly, Kevin
Spanos, Costas
Bayen, Alexandre
2015

Sensing by proxy, as described in this study, is a sensing paradigm which infers latent factors by “proxy” measurements based on constitutive models that exploit the spatial and physical features in the system. In this study, we demonstrate the efficiency of sensing by proxy for occupancy detection based on indoor CO2 concentration. We propose a link model that relates the proxy measurements with unknown human emission rates based on a data-driven model which consists of a coupled Partial Differential Equation (PDE) – Ordinary Differential Equation (ODE) system. We report on several...

Continuous Adjoint Method for Air Traffic Flow Management

Strub, Issam S.
Bayen, Alexandre M.
2006

This article develops a model of air traffic flow using an Eulerian description with hyperbolic partial differential equations. Existence and uniqueness (well-posedness) of a solution to the system of partial differential equations on a network is established. Subsequently, an optimal control problem is studied with the junction coefficients as control variables. We use a continuous adjoint approach and we implement it on a network with 16 links and 5 junctions, demonstrating the computational efficiency of this method

Modeling and Optimization Analysis of Single Flagellum Bacterial Motion

Lobaton, Edgar
Bayen, Alexandre M.
2007

Bacteria such as Rhodobacter sphaeroides use a single flagellum for propulsion and change of orientation. Simple organisms such as this have inspired nanorobotic designs with potential applications in medicine which motivates the present work. In this article, an elastic model for a single flagellum bacterium is presented and followed by an analysis of the system based on optimization. The model is based on the method of Regularized Stokeslet which allows for a discretization of the system into particles which are connected by spring forces. An optimal elasticity distribution that...