Juan Carlos Herrera

Virtual trip lines for distributed privacy-preserving traffic monitoring

Automotive traffic monitoring using probe vehicles with Global Positioning System receivers promises significant improvements in cost, coverage, and accuracy. 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 propose a system based on virtual trip lines and an associated cloaking technique. Virtual trip lines are geographic markers that indicate where vehicles should provide location updates. These markers can be placed to avoid particularly privacy sensitive locations. They also allow aggregating and cloaking several location updates based on trip line identifiers, without knowing the actual geographic locations of these trip lines. Thus they facilitate the design of a distributed architecture, where no single entity has a complete knowledge of probe identities and fine-grained location information. We have implemented the system with GPS smartphone clients and conducted a controlled experiment with 20 phone-equipped drivers circling a highway segment. Results show that even with this low number of probe vehicles, travel time estimates can be provided with less than 15% error, and applying the cloaking techniques reduces travel time estimation accuracy by less than 5% compared to a standard periodic sampling approach.

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

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 lines which are geographic markers that indicate where vehicles should provide speed updates. These markers are placed to avoid specific privacy sensitive locations. They also allow aggregating and cloaking several location updates based on trip line identifiers, without knowing the actual geographic locations of these trip lines. Thus, they facilitate the design of a distributed architecture, in which no single entity has a complete knowledge of probe identities and fine-grained location information. We have implemented the system with GPS smartphone clients and conducted a controlled experiment with 100 phone-equipped drivers circling a highway segment, which was later extended into a year-long public deployment.

Real-Time Merging Traffic Control at Congested Freeway Off-Ramp Areas

This study presents a real-time merging traffic control algorithm to mitigate the problem of freeway congestion resulting from an overspilling off-ramp. The proposed control algorithm aims at maximizing the merge area outflow of the surface street and at the same time preventing the off-ramp queue spillover into the freeway mainstream and the resulting freeway congestion. The potential benefits obtained by applying the proposed control concept are demonstrated by the use of microscopic simulation applied to a real freeway network where recurrent freeway traffic congestion is created as a result of an overspilling off-ramp. The simulation results demonstrated that the proposed control algorithm may improve the prevailing traffic conditions, preventing the formation of freeway congestion and benefiting freeway drivers and surface street users.

Using Travel Time Data to Generate Aggregated Measures of Traffic

Reliable travel time data are easier to obtain than they were a few years ago because of technological advances. These data are used by drivers to plan their trips and by agencies to monitor traffic. However, travel time data are usually collected from a certain sample of all the vehicles traveling on the road. This paper proposes a simple and effective methodology for obtaining more information from these types of data. The method uses travel time data to construct cumulative curves at two points on a road section. Aggregated measures such as arrival flow and total delay then can be computed. This method is a simpler way to assess the social cost of congestion caused by various bottlenecks and adds value to travel time data.

UNSETTLING THE GEOGRAPHY OF OAKLAND'S WAR ON POVERTY

Historical studies of the War on Poverty have overwhelmingly focused on its consequences in African American communities. Many studies have grappled with how War on Poverty innovations co-opted a thriving African American social movement. This paper explores the impact of War on Poverty programs on the development of a political cadre of Mexican American grassroots leaders in Oakland, California. It investigates how coordinated 1960s protests by Mexican American organizations reveal Oakland’s changing racial0ethnic conditions and shifting trends in the state’s relationship to the urban poor. It demonstrates how a national shift to place-based solutions to poverty devolved the “problem of poverty” from the national to the local level and empowered a new set of actors—community-based organizations—in the fight against poverty. This essay argues that the devolution of federal responsibility for welfare provided the political and institutional opening for the rise of powerful Mexican American organizations whose goal was the recognition of a “Mexican American community” meriting government intervention. This essay also demonstrates how Mexican American organizations mobilized in relation to African American social movements and to geographies of poverty that were deemed exclusively Black.

Cruces de fronteras, identidades indígenas, género y justicia en las Américas

This paper analyzes and reflects on the deep transformations currently suffered by indigenous communities under the neoliberal globalization regime, as well as the way in which indigenous people articulate as subjects of law under this context in different regions of Mexico, Guatemala and the United States (including the transnational experiences of indigenous migrants between these countries).