OTREC research examines ways to anonymize location data

A new OTREC report explores an innovative technique for making household travel data more widely available without compromising individual privacy.
 
Public agencies spend vast amounts of money collecting information in household travel surveys.
 
In the report, Wider Dissemination of Household Travel Survey Data Using Geographical Perturbation Methods, lead investigator Kelly Clifton of Portland State University examines ways to make that information more accessible by planners and other professionals.
 
Survey respondents are guaranteed anonymity in exchange for their participation. In addition to asking which modes individuals use to get around, surveys learn where they live, where they work, their household sizes and demographic information.
Detailed geospatial referencing of the home, work and other travel destinations is common practice.
Such data can be of enormous use to planning professionals, but its dissemination must be balanced with the need to keep locations confidential.
 
To protect this confidentiality, data are often aggregated to a geographic level such as census tracts or transportation analysis zones (TAZs) before being publicly shared.
This limits the utility of the information. Details are lost with data aggregation. For example, walking trips can be affected to a large degree by the built environment. If all pedestrian trips are aggregated up to a larger zone, then questions about how they were affected by the built environment cannot be answered.
To allow more precise data to be more widely distributed without sacrificing participants’ anonymity, Clifton took a deep look into other geographical masking methods.
 
With the help of graduate student researcher Steven Gehrke, Clifton reviewed various methods of geo-masking, also known as geographical perturbation.
Their goal was to develop a conceptual framework to guide geographical perturbation efforts.
After looking into several methods, they tested one of the more promising methods by actually using it on household survey data for the Portland, Ore. metropolitan region.
With this process, researchers aimed to quantify the concepts of disclosure risk and data utility, in order to improve the understanding of their tradeoff.
The method they chose for empirical testing is known as the donut masking technique.
In this technique, as shown in the image below, a “donut” is defined around each protected point.
The inner ring of the donut, with the protected location in the center, is the anonymity zone: public records will not show that the point is located anywhere within that circle.
The boundary of the donut’s outer ring is defined by the data custodian; in urban contexts, it usually corresponds to an accessible walking distance. In more rural contexts, the outer ring may need to extend further where there is less population density.
The data points are then randomly re-distributed on a map so that they fall somewhere within the donut, between the inner and outer rings.
When the material becomes public, planners and other professionals will have more spatially sensitive information, without having access to the true locations of an individual’s home or workplace.
 
To test the donut masking technique, Clifton's team used it to explore the connections between 4,824 households and five measures of the built environment in the Portland, Ore. metro region.
They analyzed 25 scenarios, and each time, conducted an analysis into the vulnerability of a sampled household to identity disclosure.
They found that data custodians using this method must be aware of a sensitive "tipping point" between disclosure risk and data utility. Guidelines for calculating the position of the inner and outer rings, and discussion of other factors to consider, can be found in the final report.
 
Visit the project page for more details.
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Light rail reduces auto traffic, cuts emissions, study finds

For the first time, researchers have shown that installing light rail on an existing travel corridor not only gets people out of their cars, but reduces congestion and air pollution.

In the study, planners at the University of Utah measured impacts of a new light rail line in Salt Lake City (University Line) on an existing major thoroughfare (400/500 South). Their analysis showed that traffic near the University has fallen to levels not seen since the 1980s, even as the number of students, faculty and staff at the university has increased, and the commercial district along the corridor has expanded.

"This is the first study to document important effects of light rail transit on traffic volumes,” said Reid Ewing, professor of city and metropolitan planning at the University of Utah and lead author on the study. “Since the University TRAX line opened, there has been increased development in the 400/500 South travel corridor, yet traffic on the street has actually declined. Our calculations show that without the University TRAX line, there would be at least 7,300 more cars per day on 400/500 South, and possibly as many as 21,700 additional cars. The line avoids gridlock, as well as saves an additional 13 tons of toxic air pollutants. This is important knowledge for shaping future transportation policies.”

Andrew Gruber, executive director of the Wasatch Front Regional Council, which has been responsible for coordinating transportation planning in the Salt Lake and Ogden areas since 1973 said, “This study further demonstrates the value of public transportation in helping people reach their destinations, reduce traffic and spur economic development. The findings are significant for local governments across our region as they consider the future of transit in their community.”

The report—which validates assumptions widely used in travel demand models used in community planning—was issued recently by the National Institute for Transportation and Communities, and has been accepted for publication in the Journal of Public Transportation later this year. The report is available for download at https://nitc.trec.pdx.edu/research/project/611.

Ewing worked with Guang Tian, a doctoral student in city and metropolitan planning, and Allison Spain, academic program manager at the University of Utah.

How the study was conducted

A “quasi-experimental” research design was used for the study, which is different from a traditional research design because it is not possible to randomly assign subjects to a treatment or control group in this setting. To compensate for lack of randomization, a variety of matched samples—traffic on parallel streets in the corridor, transit ridership, development and related traffic—was used to confirm the results.

In this case, the first treatment was a 2.3 mile extension of TRAX from downtown Salt Lake City to the University of Utah stadium built in 2001. Comparing data from 2001 and 2002 provided a way to study effects on the travel corridor before and after construction. Likewise, the 1.5 mile extension from the stadium to the University Medical Center, begun in 2002 and completed in 2003, provided another comparison—before treatment in 2003 and after in 2004.

Annual average daily traffic (AADT) on 400/500 South decreased by 9,300 vehicles as net transit ridership increased 7,200 in 2002 over 2001 before the TRAX line was built. Researchers attributed the changes to the TRAX extension because AADT increased only slightly on parallel streets.

Considering growth in the area and coincident traffic impacts produced a surprising finding.

“We assumed that without TRAX, traffic on 400 South would have increased as a function of development in the area,” said Ewing. “Instead, we found just the opposite. As the corridor became more developed over the decade—concurrent with the opening of TRAX—traffic actually declined.”

Total development, as measured by building floor area, increased by nearly 13 percent between 1999 and 2009, from 50.6 million square feet to 57.0 million square feet. Comparing the estimated traffic volume that would be associated with that growth, and the actual traffic volumes measured in 2009 showed an estimated decrease in average daily traffic by 21,700 trips.

Applying Environmental Protection Agency calculations for fuel consumption and average emissions for passenger cars to that number of trips, TRAX contributes to saving 1,000 gallons gasoline and avoiding 19,400 pounds CO2 emissions daily. On an annual basis, this means saving 364,300 gallons of gasoline and 7.1 million pounds of CO2.

“An important caveat is that while the results of this study are revealing and important for future planning, we cannot guarantee that light rail transit would have the same effect on traffic at other locations,” Ewing concluded. “The study area in Salt Lake City is unique, with the university as a major employer is the area and students and staff having free access to transit. The comparison group in this study is not identical to the experimental group, but we believe the estimates established to test our hypotheses support the results.”

The study was done in coordination with the Utah Transit Authority (UTA), Wasatch Front Regional Council (WFRC), and the Utah Department of Transportation (UDOT), and is available for download at https://nitc.trec.pdx.edu/research/project/611.

"UDOT found the results from the ‘Report on the Effect of University TRAX on traffic along 400/500 South’ interesting,” said Jeff Harris, planning director for UDOT. “While it is difficult to make direct causal connections from the results of one study, these results, along with the ridership on the University TRAX line and the UTA reported transit mode share to the University, do indicate that TRAX is having a positive impact. UDOT believes in the importance of and is committed to developing an integrated transportation system. We look forward to working with our partners in the future to conduct this type of research and help build a body of knowledge about the positive effects of implementing integrated transportation solutions."

Making TRAX in Utah

The first light rail line in Salt Lake was opened in 1999, and an extension from the downtown to the University of Utah was completed in 2001with a further expansion to the University Medical Center in 2003. Several additions have been made system-wide since that time. The current study focused on the University extension because ample time has passed to measure its full effect, and because it has the highest ridership in the system.

“The University LRT Line was developed through a strong partnership between Utah Department of Transportation, Utah Transit Authority, Salt Lake City, University of Utah, Wasatch Front Regional Council, Federal Transit Administration, the Salt Lake Chamber and area businesses,” noted Michael Allegra, UTA general manager.  “The University LRT Line in 2001 has resulted in stabilized traffic flows, increased economic investment in the corridor and significant increases in transit ridership.” 

The study was supported by the National Institute for Transportation and Communities.

Portland State University students enhance Tigard'’s walkability

Several notable transportation projects have come out of Portland State University’s Master of Urban and Regional Planning (MURP) program this spring.

 

Each year, graduating students finish up their two-year program of study by forming into groups and carrying out a professional project. Clients work with Portland State University to identify planning needs that would be a good fit for the MURP program, and students choose projects based on their interests.

 

The Paradigm Planning team made news with their re-imagining of the Salem-Keizer transit system, and InSite Planning Group with their Beaverton corridor study.

 

The city of Tigard engaged StepUP Studio, another MURP team, to craft a pedestrian plan.

 

StepUP Studio comprises team members Chase Ballew, Mark Bernard, Jeremy Dalton, Laura Goodrich, Szilvia Hosser-Cox and Steven McAtee.

 

Their challenge was to make Tigard, Ore.—a city of roughly 48,000 people with three highways running through it—into a walkable place.

 

The group met with the Tigard City Council March 18 to introduce them to the project. Their proposal for increasing walkability with a heavy reliance on community input supports the city of Tigard’s 2014 Strategic Vision, as well as their Comprehensive Plan goal for citizen involvement.

 

StepUP Studio’s community engagement strategies included intercept and online surveys, social media, resident interviews, open houses, walking tours, public presentations and community conversations.

 

On May 11, the team went to Tigard’s first Farmer’s Market of the year and talked about walkability strategies with people there, to raise awareness about their project and about other community engagement opportunities.

 

They worked with Kittleson and Associates, Inc. to create an interactive online map showing many of Tigard’s pedestrian and bicycle routes, with the opportunity to select a route and leave comments.

 

Tigard pedestrians reacted with enthusiastic input, leaving pages of comments. They compared notes on the best trails to walk, as well as pointing out sections that don’t connect, places where sidewalks and bike paths end, and intersections that have issues with unsafe crossing.

 

  • The final plan, which StepUP presented June 11 to the Tigard Office of Community Development, is available for download here.

 

The plan outlines five complementary strategies that are designed to be low-cost, outside-the-box solutions to enhance the city’s walkability.

 

The five strategies are:

 

1. Neighborhood Centers

 

Tigard's zoning laws allow for mixed-use commercial and residential neighborhood centers, which would provide residents with local destinations to walk to, but few exist. StepUP provided recommendations for where new neighborhood destinations could do the most good.

 

2. Active Parks and Trails

 

Parks and trail systems are already the heart of Tigard's pedestrian network. The students put together a guidebook of activities such as walks and runs, community gardens, or summertime movies under the stars to give area residents more reasons to use them.

 

3. Talk the Walk

 

With its crisscrossing trails and central downtown, Tigard is already more walkable than most people realize. The team provided materials for communication and education strategies to raise awareness and enthusiasm about walking.

 

4: Safe Routes to School

 

Students connected city staff with Kari Schlosshauer, the Pacific Northwest's regional policy manager for the Safe Routes to School program, and provided examples from other cities of how the program works.

 

5. Simple Signs

 

Much of Tigard's existing walkable infrastructure is unknown even to nearby residents, in part because neighborhoods often lack adequate signage directed at people on their feet. The team gave recommendations for simple, visible, and frequent signs to help walkers feel more confident about knowing where they're going and how long it will take.

 

Jeremy Dalton, the group’s communication specialist, is excited that Tigard has put walkability at the forefront of its new, updated Strategic Plan, and that StepUP Studio’s work plan seems to fit in with that the client wants.

 

“We got very positive feedback from the city,” Dalton said.

 

Tigard already has a prioritized plan for connecting the pedestrian network, putting in new sidewalks where they are most needed. The strategies provided by StepUP Studio are designed to help make the most of the existing and new infrastructure.

OTREC researchers will present on bike/ped counts at traffic data conference

OTREC researchers Krista Nordback and Sirisha Kothuri will present research at the North American Travel Monitoring Exposition and Conference (NATMEC) from June 29 to July 2, 2014.

The conference, organized by the Transportation Research Board, provides an opportunity for traffic monitoring professionals to share information about collecting and using traffic data.

Nordback will talk about what professionals can do to maintain bicycle count programs at the state level. She will give a presentation on the feasibility of using existing traffic signals to collect bicycle counts, and on what to do with that data once it is gathered.

Kothuri will present strategies for counting pedestrians using existing resources such as signal controllers and software already installed at intersections.

Nordback and Kothuri will draw from their own research as well as from the work of Miguel Figliozzi, Chris Monsere, Pam Johnson and Bryan Blanc in their ODOT report, Developing a Statewide Bicycle and Pedestrian Data Collection System in Oregon.

The conference, an international venue for sharing experiences on effectively monitoring traffic flow, will be held at Swissôtel in Chicago, Illinois.

Student planning project yields professional results for Beaverton

Portland State University’s Master of Urban and Regional Planning (MURP) program matches students with clients every year to execute professional-level planning projects.

 

This spring, InSite Planning Group, a team of six MURP students, conducted a detailed corridor study for the city of Beaverton.

 

The study area, which extends for 1.6 miles along Beaverton's Allen Boulevard, is home to diverse, vulnerable populations and a number of small businesses. The four-lane corridor was identified by the city of Beaverton as a candidate for an in-depth planning strategy.

 

Team members JP McNeil, Anna Wendt, Art Graves, August Benzow, Samantha Petty and Taren Evans took on the challenge of creating a commercial corridor vision plan for Allen Boulevard, something that would serve as a guide for corridor improvements and future development.

 

They focused on three main areas: incorporating the community’s needs and values, furthering transportation and economic development goals and limiting the displacement of existing homes and businesses.

 

They started by interviewing 10 local professionals—in a range of professions from police offers to forestry experts—whose expertise they drew on for an understanding of the existing conditions on Allen. The interviews gave the students access to a technical knowledge base in areas like community policing and code enforcement, family and community resources, parks and recreation, and streetscaping.

 

To reach out to business owners and residents who would be affected by changes, team members conducted a community survey on paper and online, and in English and Spanish. They also surveyed local business owners and customers. Through publicity materials like posters and flyers, social media, and the project’s website, the team hoped to engage as many residents as possible in making decisions about the future of Allen Boulevard.

 

They arranged to have a table at the Beaverton Farmers Market on March 15, so that they could reach people who otherwise might not have heard of the project. They also held focus groups, an open house on March 20, and a public meeting on April 24 where community members were invited to hear ideas and offer feedback.

 

Based on the community feedback, Insite Planning Group came up with a comprehensive plan to improve the neighborhood’s safety, vitality, and sense of identity.

 

The corridor had been described by residents as uncomfortable to walk along. Narrow lanes, lack of a median, and a relative scarcity of crosswalks make it dangerous to cross, while graffiti and the occasional presence of garbage (couches, old appliances) along the street further detract from the pedestrian experience.

 

By orchestrating storefront improvements, tree-planting programs, neighborhood cleanup days, and community-supported art, Allen Blvd and its local businesses could communicate that it is a welcoming and vibrant commercial area.

 

Improvements to the pedestrian infrastructure are also recommended; the plan encourages a mix of land uses that support pedestrian safety and comfort, while also contributing to commercial district identity and economic development. With mixed commercial and medium-to-high-density residential districts, the work of InSite planners along Allen Boulevard will likely coincide with the goals that Metro has outlined for 2040.

 

  • Their final plan, which they will present to the city of Beaverton on June 25, is available for download here.

Once Beaverton staff has reviewed the project for approval, the plan will feed into Beaverton’s Comprehensive Plan update (scheduled for adoption in Spring 2016) and its long-range planning for Allen Boulevard.