ITS Berkeley

Analytical and Grid-Free Solutions to the Lighthill–Whitham–Richards Traffic Flow Model

Mazaré, Pierre-Emmanuel
Dehwah, Ahmad H.
Claudel, Christian G.
Bayen, Alexandre M.
2011

In this article, we propose a computational method for solving the Lighthill–Whitham–Richards (LWR) partial differential equation (PDE) semi-analytically for arbitrary piecewise-constant initial and boundary conditions, and for arbitrary concave fundamental diagrams. With these assumptions, we show that the solution to the LWR PDE at any location and time can be computed exactly and semi-analytically for a very low computational cost using the cumulative number of vehicles formulation of the problem. We implement the proposed computational method on a representative traffic flow scenario...

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...

Individual Speed Variance in Traffic Flow: Analysis of Bay Area Radar Measurements

Blandin, Sébastien
Salam, Amir
Bayen, Alexandre
2012

The recent increase of mobile devices able to measure individual vehicles speed and position with high accuracy brings new opportunities to traffic engineers. The large amount of individual probe measurements allows the study of phenomena previously unobservable with conventional sensing technologies, and the design of novel traffic monitoring and control strategies. However, challenges inherent to the use of speed and location data arise. One of the main difficulties of measurements collected from individual vehicles lie in their ability to provide relevant information on the...

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...

A Tractable Class of Algorithms for Reliable Routing in Stochastic Networks

Samaranayake, Samitha
Blandin, Sébastien
Bayen, A.
2012

The goal of this article is to provide the theoretical basis for enabling tractable solutions to the “arriving on time” problem and enabling its use in real-time mobile phone applications. Optimal routing in transportation networks with highly varying traffic conditions is a challenging problem due to the stochastic nature of travel-times on links of the network. The definition of optimality criteria and the design of solution methods must account for the random nature of the travel-time on each link. Most common routing algorithms consider the expected value of link travel-time as a...

Enhancing Privacy and Accuracy in Probe Vehicle-Based Traffic Monitoring via Virtual Trip Lines

Hoh, Baik
Iwuchukwu, Toch
Jacobson, Quinn
Work, Daniel
Bayen, Alexandre M.
Herring, Ryan
2012

Traffic monitoring using probe vehicles with GPS receivers promises significant improvements in cost, coverage, and accuracy over dedicated infrastructure systems. Current approaches, however, raise privacy concerns because they require participants to reveal their positions to an external traffic monitoring server. To address this challenge, we describe a system based on virtual trip lines and an associated cloaking technique, followed by another system design in which we relax the privacy requirements to maximize the accuracy of real-time traffic estimation. We introduce virtual trip...