Data

Mobile Millennium: GPS Mobile Phones as Traffic Probes, California Networked Traveler - Safe Trip 21 Phase II

Bayen, Alexander M.
2011

Recent advances in mobile devices and internet technology have led the California Department of Transportation (Caltrans) to investigate a data collection solution that offers improved data reliability and availability at a significantly lower cost. It has been postulated that information from GPS cell phones could provide position and speed data -- referred to as probe data -- for highways and arterials in near real time over much of the transportation network. The Mobile Millennium project was established to determine if the collection and use of probe data for traveler information...

An Adaptive Routing System for Location-Aware Mobile Devices on the Road Network

Borokhov, Paul
Blandin, Sébastien
Samaranayake, Samitha
Goldschmidt, Olivier
Bayen, Alexandre M.
2011

As congestion problems become a greater concern and negatively impact society, solutions which alleviate them are needed to improve the performance of the transportation system. Routing systems which take into account the travel-time experienced by the driver have been largely unexplored in the domain of adaptive routing. In this article, we present a system which enables users of smartphones to obtain directions generated using an algorithm which provides an optimal routing policy for reliable on-time arrival; that is, directions which seek to maximize the probability of arriving to the...

Online Least-Squares Estimation of Time Varying Systems with Sparse Temporal Evolution and Application to Traffic Estimation

Hofleitner, A.
El Ghaoui, L.
Bayen, A.
2011

Using least-squares with an l1-norm penalty is well-known to encourage sparse solutions. In this article, we propose an algorithm that performs online least-squares estimation of a time varying system with a l1-norm penalty on the variations of the state estimate, leading to state estimates that exhibit few “jumps” over time. The algorithm analytically computes a path to update the state estimate as a new observation becomes available. The algorithm performs computationally efficient and numerically robust state estimation for time varying systems in which the dynamics are slow compared to...

iShake: Mobile Phones as Seismic Sensors -- User Study Findings

Ervasti, Mari
Dashti, Shideh
Reilly, Jack
Bray, Jonathan D.
Bayen, Alexandre
2011

The "iShake" system uses smartphones as seismic sensors to measure and deliver ground motion intensity parameters produced by earthquakes more rapidly and accurately than currently possible. Shaking table tests followed by field trial with approximately 30 iShake users were implemented to evaluate the reliability of the phones as seismic monitoring instruments and the functionality of the iShake system. In addition, user experiences were investigated with 59 iShake users, who provided feedback through a mobile questionnaire. Research included participative planning with a focus group to...

Three-Stream Model for Arterial Traffic

Bails, Constant
Hofleitner, Aude
Xuan, Yiguang
Bayen, Alexandre M.
2012

In this article, a new analytical traffic flow model is proposed for traffic dynamics at signalized intersections. During each cycle, both the arrival and the departure traffic are approximated by three distinct traffic streams with uniform density. Because of the similar representation of the arrival and the departure traffic, results from a single intersection can easily be extended to a series of intersections. With this model, the number of parameters of the model is tractable, leading to analytical solutions of the problem. It also is proved that the total delay of one-way...

Large-Scale Estimation of Arterial Traffic and Structural Analysis of Traffic Patterns from Probe Vehicles

Hofleitner, Aude
Herring, Ryan
Bayen, Alexandre
Han, Yufei
2012

Estimating and analyzing traffic conditions on large arterial networks is an inherently difficult task. The first goal of this article is to demonstrate how arterial traffic conditions can be estimated using sparsely sampled GPS probe vehicle data provided by a small percentage of vehicles. Traffic signals, stop signs, and other flow inhibitors make estimating arterial traffic conditions significantly more difficult than estimating highway traffic conditions. To address these challenges, a statistical modeling framework is proposed that leverages a large historical database and...

Probability Distributions of Travel Times on Arterial Networks: Traffic Flow and Horizontal Queuing Theory Approach

Hofleitner, Aude
Herring, Ryan
Bayen, Alexandre
2012

In arterial networks, traffic flow dynamics are driven by the presence of traffic signals, for which precise signal timing is difficult to obtain in arbitrary networks or might change over time. A comprehensive model of arterial traffic flow dynamics is necessary to capture its specific features in order to provide accurate traffic estimation approaches. From hydrodynamic theory, arterial traffic dynamics are modeled under specific assumptions standard in transportation engineering. This flow model is used to develop a statistical model of arterial traffic. The statistical approach...

Trade-offs Between Inductive Loops and GPS Probe Vehicles for Travel Time Estimation: Mobile Century Case Study

Mazaré, Pierre-Emmanuel
Tossavainen, Olli‐Pekka
Bayen, Alexandre M.
Work, Daniel B.
2012

This article addresses the trade-offs between (i) velocity data collected from GPS smartphones in probe vehicles, and (ii), velocity data obtained from inductive loop detectors, for the purpose of computing travel times on a stretch of roadway. It is a case study which uses experimental data collected on one day in the San Francisco Bay Area, obtained as part of a 2008 field experiment known as Mobile Century. Estimates of the traffic velocity field are constructed using a velocity model equivalent to the Cell Transmission Model, and a traffic state estimation algorithm known as...

Exponential Stability of Switched Linear Hyperbolic Initial-Boundary Value Problems

Amin, Saurabh
Hante, Falk M.
Bayen, Alexandre M.
2012

We consider the initial-boundary value problem governed by systems of linear hyperbolic partial differential equations in the canonical diagonal form and study conditions for exponential stability when the system discontinuously switches between a finite set of modes. The switching system is fairly general in that the system matrix functions as well as the boundary conditions may switch in time. We show how the stability mechanism developed for classical solutions of hyperbolic initial boundary value problems can be generalized to the case in which weaker solutions become necessary due to...

Reconstruction of Boundary Conditions from Internal Conditions Using Viability Theory

Hofleitner, A.
Claudel, C.
Bayen, A.
2012

This article presents a method for reconstructing downstream boundary conditions to a HamiltonJacobi partial differential equation for which initial and upstream boundary conditions are prescribed as piecewise affine functions and an internal condition is prescribed as an affine function. Based on viability theory, we reconstruct the downstream boundary condition such that the solution of the Hamilton-Jacobi equation with the prescribed initial and upstream conditions and reconstructed downstream boundary condition satisfies the internal value condition. This work has important...