Data

Mobile Transit Trip Planning with Real-Time Data

Jariyasunant, Jerald
Work, Daniel B.
Kerkez, Branko
Bayen, Alexandre M.
2011

In this article, we describe the development of a transit trip planner (TTP) for mobile devices called Transitr, and evaluate its performance. The system predicts the shortest paths betweenany two points in the transit network using real-time information provided by a third party busarrival prediction system, relying on GPS equipped transit vehicles. Users submit their originand destination through a map-based iPhone application, or through a JavaScript enabled web browser. A server implementing a dynamic K-shortest paths algorithm with predicted link travel times returns personalized...

State Estimation and Modeling Error Approach for 2-D Shallow Water Equations and Lagrangian Measurements

Tossavainen, Olli‐Pekka
Percelay, Julie
Stacey, Mark
Kaipio, Jari P.
Bayen, Alexandre M.
2011

A state estimation method for two-dimensional shallow water equations (SWE) in rivers using Lagrangian drifter positions as measurements is proposed. Lagrangian drifters are sensors moving with the flow and reporting their location. The aim of this method is to compensate for the lack of accurate information about boundary conditions. The drifters move with the local flow and report their positions. Thus, they provide additional information about the state of the river compared to a case in which, for example, only a computational model is used to describe the river flow. In this work, the...

Convex Formulations of Data Assimilation Problems for a Class of Hamilton–Jacobi Equations

Claudel, Christian G.
Bayen, Alexandre M.
2011

Extending and improving some recent results of Hantoute, López, and Zălinescu and others, we provide characterization conditions for subdifferential formulas to hold for the supremum function of a family of convex functions on a real locally convex space.

Combined State-Parameter Estimation for Shallow Water Equations

Rafiee, Mohammad
Tinka, Andrew
Thai, Jérôme
Bayen, Alexandre M.
2011

In this article, a method for assimilating data into the shallow water equations when some of the model parameters are unknown is presented. The one dimensional Saint-Venant equations are used as a model of water flow in open channels. Using these equations, a nonlinear state space model is obtained. Lagrangian measurements of the flow velocity field are used as observations or measurements. These measurements may be obtained from a group of drifters equipped with GPS receivers and communication capabilities which move with the flow and report their position at every time step. Using the...

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...