Transportation / Transportation Study Research Methodology

Scope

At the recommendation of our internal NRDC advisers, we chose U.S. census defined metropolitan regions as the official unit of the study and scale for our data collection. Regional data is the most comprehensive means of analyzing the effectiveness of a city’s transportation system as it encompasses the sprawling outer suburbs, where the biggest transportation challenges lie.

We then classified all U.S. metropolitan regions in three population sizes—those with populations of less than 250,000 (referred to as “small regions”), those with populations of 250,000 to 1 million (referred to as “medium regions”), and finally regions with populations of 1 million and more (referred to as "large regions").

Primary Data Sources

Center for Neighborhood Technology

In seeking the best sources of transportation data across all U.S. metro regions, Smarter Cities partnered with the Center for Neighborhood Technology (CNT), an organization which collects and analyzes data for all 337 of the nation’s U.S. census defined metropolitan regions, covering more than 80% of the U.S. population.

CNT, a longtime collaborator with NRDC, is a creative think-and-do tank that combines rigorous research with effective solutions. CNT works across disciplines and issues, including transportation and community development, energy, natural resources, and climate change. For this study, we drew specifically on the extensive data sets assembled by their Housing + Transportation Affordability Index. 

We collaborated with CNT to develop a set of eight key transportation indicators to compare large, medium and small U.S. metro regions. We then grouped these eight indicators into three categories, listed here with explanatory text:

1. Transit Access

• Number and Percent of Households with Access to Transit – Households that are located within a ¼ mile buffer of a bus route (or stop) or a ½ mile buffer of a rail station are considered to have access to transit. Regions where CNT does not have transit data are not included in this ranking.
• Number and Percent of Households Living in Neighborhoods (Block Groups) with Access to Good Levels of Transit – Within population categories, CNT’s Transit Access Index (TAI) block groups values were grouped into poor, medium and good transit access levels. All block groups in the appropriate regions (according to population) with any level of transit access were broken up into three levels with approximately equal counts of households per tertile. The top third for each population group were defined as having “good access.” The number of households in block groups with good transit access were aggregated to regions.

2. Transit Use Versus Auto Use

• Number and Percent of Commuters Using Transit to Get to Work – 2000 Census data on the number of workers using transit in each block group were aggregated to regions. ‘Total commuters’ is the count of total workers excluding individuals who work from home.
• Average Auto Ownership – Weighted average (i.e. weighted by households) of 2000 Census data on the average number of vehicles per household in each block group.
• Average Household VMT – Weighted average (weighted by households) of the average annual VMT per household in each block group.  VMT was modeled using block group level data as part of CNT's H+T Index.

3. Transportation Affordability

• Number and Percent of Households Living in Neighborhoods (Block Groups) Where Transportation Costs are Less than or Equal to 15% of Household Income – Number of households in block groups where local transportation costs are less than 15% of median household income aggregated to regions.
• Average Annual and Monthly Household Transportation Costs –Weighted average (weighted by households) of the average local monthly transportation costs in each block group. Typically an indicator of a quality transit system, compact development patterns and access
• Number and Percent of Block Groups Where Transportation Costs are Less than or Equal to 18% of Area Median Income – Count of block groups in each region where transportation costs for the typical regional household are less than 18% of area median income.

Brookings Metropolitan Policy Program: State of Metropolitan America

For the most recent commuting data and trends for the nation’s 100 largest Metropolitan Statistical Areas, we turned to the Brookings Metropolitan Policy Program’s data resources, specifically the State of Metropolitan America Indicator Map. The State of Metropolitan America report “portrays the demographic and social trends shaping the nation’s essential economic and societal units—its large metropolitan areas—and discusses what they imply for public policies to secure prosperity for these places and their populations,” according to its purpose statement.

We found this resource particularly useful for cross-referencing the CNT's data  (based predominantly on the 2000 U.S. census) for our large metro regions with up to date commuting data from 2009 and trend data between 2000-2009. We focused on three indicators from the State of Metropolitan American Indicator Map, listed here:

1. 2009 Largest Percentage of Workers Commuting By Public Transportation
2. 2009 Smallest Percentage of Workers Commuting By Driving Alone
3. Increase In Share of Workers Commuting By Pubic Transportation, 2000-2009

Top Performing Anomalies

Portland, Oregon

Portland did not meet our large region criteria, however its innovative and sustainable programs put it among our top performing city/metro regions. Upon further investigation we found that Portland metro region doesn’t show up as a high scorer across several indicators because it’s so large with its impressive policies focused only on the city, within its urban growth boundary. Our data thresholds are imperfect because they require region-wide transportation success across multiple indicators without accounting for pockets of outstanding innovative policies at the city or municipality level. Portland’s city-based transportation programs are unparalleled and have had remarkable results. Between 1996 and 2006, average vehicle miles traveled in the city of Portland grew only 19 percent while population grew 27 percent. In that same period, transit ridership grew three times faster than transit service increases and approaching twice as fast as population. In order to adhere to our original purpose of identifying and profiling leaders in innovative transportation policy we included Portland as a top performing city/metro region.

Los Angeles, California

Los Angeles met all of our large region data thresholds and our sustainable policy threshold, and yet we are not including it among the nation's Top Performing cities. Our reasons are multi-fold: Though it gets good marks for high transit access, low transportation costs, and the percentage of commuters using transit has increased over the last decade, the region most well known for bumper-to-bumper traffic still has many challenges for integrating sustainable transportation across the region. Los Angeles ranks number one in the nation for traffic delay, by a large margin. The American Lung Association ranks Los Angeles as worst in the nation for ozone pollution, third worst in the nation for year round particle pollution and fourth worst for short-term particle pollution, all auto-exhaust pollutants. And despite being one of only two regions in the nation (the other being Boston) with a transit system employing all five of the major transit vehicle types – regional rail, subway, light-rail, electric trolley buses, and motor buses – transit ridership in Los Angeles is only at 6 percent of the total commuting population. Read more about what Los Angeles is doing on transportation in its ‘City to Watch’ story.

Identifying High Performing Metro Regions

Starting with CNT’s comprehensive and reputable data set, we made our first cut to our overall list of 337 metro regions based on the three categories of agreed-upon indicators. CNT compiled a spreadsheet of the top 20 small, medium and large metro regions in the nation for each of the eight indicators that fall within one of the three categories – transit access, transit use vs. auto use, and transportation affordability.

We then selected criteria to pare down the list of metro regions to a more manageable size based on a history of high performance across the key transportation indicators including: high transit access and use; low average household automobile ownership and use; and low average household transportation costs. We require that all regions must show region-wide success in more than one of these categories of indicators, for example, in high transit access and low transportation costs. Therefore, a region with very low vehicle miles traveled and low auto ownership will not meet the criteria as both of these indicators are in the same category. Our criteria and the metro regions that meet them are listed in the High Performance Data Table.

Large Metro Region Criteria

Large metro regions often have more resources to devote to improving and expanding their transportation systems, which can make it more difficult to identify clear leaders amongst a group of regions with impressive programs.  For this reason we required large regions to rank highly in both the CNT data and the Brookings State of Metropolitan America data in order to make the cut.

First, large regions must rank in the top 15 in the nation for indicators within at least two of the three categories of CNT data. Second, the region must also rank in the top 15 in the nation for two the State of Metropolitan America 2009 indicators (highest percentage of commuters using public transit and lowest percentage of commuters driving to work alone) and must have an increase in percentage of commuters using public transit to get to work between 2000 and 2009 (thought doesn’t have to rank in the top 15). Large regions will therefore qualify by meeting five out of six criteria.

For example, Boston, Massachusetts, appears in the top 15 for transit access, transit use vs. auto ownership and transportation affordability based on high ranking in CNT’s ‘good transit’, ‘auto ownership’, ‘average household transportation costs’ and ‘transportation affordability’ indicators. Boston also ranks in the top 15 for most commuters using transit, least commuters driving to work alone, and has an increase in overall commuters using transit, according to all three criteria for the State of Metropolitan America indicators. Therefore Boston met all six criteria, though only five are required to be a high performing large region.

Medium and Small Region Criteria

As the Brookings State of Metropolitan America data focuses only on the largest U.S. metro regions, we were unable to use both data sets to narrow down the list of medium and small regions. We therefore only used CNT data to compare medium and small regions. However, we required these regions rank in the top 15 in the nation (for their population group) for all three categories of CNT data.*

*CNT does not have Transit Access data for Bremerton, Washington. Nonetheless, we selected Bremerton as a Smarter City for transportation due to the unique characteristics of its vanpool transit system that allows residents to sign up for a vanpool anywhere in the region. Given the scope and flexibility of this bus service region-wide Bremerton has near complete transit access, which also likely bolsters the region's top ranking for transit use.  

High Performing Metro Regions

Using these data criteria we were able to narrow down our lists of metro regions to the top large, medium and small regions. In sum, large regions must meet five out of six data criteria based on two data sets combined, while medium and small regions must meet all three data criteria based only on the CNT data set. This gave us a list of approximately 30 high performing metro regions for transportation in the nation based on this basic selection of indicators.

Identifying Top Performers

To identify the top performing cities/metro regions for transportation we researched each of the metro regions on our short list of high performing regions in search of standout innovative and sustainable transportation policies and programs. Our final criteria required the principal transit authority in each city/metro region to integrate a minimum of three sustainable programs with its overall transportation policies. 

While there is no single accepted definition of ‘sustainable transportation’ there is a wealth of literature on the subject (see the selection of references below). According to the U.S. Department of Transportation sustainable transportation programs target five key issues: improving air quality, reducing greenhouse gas emissions, facilitating compact development to conserve land and decrease travel demand, saving energy and minimizing environmental impacts.

Examples of sustainable transportation programs include:

• complete streets or multimodal infrastructure systems that provide easy access for all types of transportation and particularly low-carbon alternatives including walking, biking and public transit;
• discounted transit passes, transit tracking services and a greater variety of widespread transit choices to incentivize lower-impact transit use;
• and highway tolls, limited parking, high parking-meter prices and other economic disincentives to discourage car use.

In order to collect as much information as possible about innovative transportation programs underway in our final regions we contacted all of our top 30 regions via email in December 2010. We invited representatives from each region to provide further information about their region’s innovative transportation policies. Emails were directed to the individual in each city/metro region’s transit authority or government who was most likely to be able to discuss transportation issues; in many cases this was a sustainability or environmental specialist, manager or planner. Where we were unable to find a specific individual to contact, we emailed the mayor’s office and we asked them to introduce us to the appropriate party.

2011 SMARTER CITIES FOR TRANSPORTATION

The 2011 Smarter Cities for Transportation include large-sized metro regions, which met or exceeded five out of six criteria, and medium and small metro regions that met three out of three criteria. The primary transit authorities in these top regions then must also have a minimum of three current sustainable transportation programs to be identified as top performers. The selected transportation leaders exhibit some the nation’s best and most innovative practices in transportation and make a strong case for the importance of a nationwide transit-focused, sustainable society. By sharing the lessons they can offer through this analysis, Smarter Cities hopes to be able to encourage comparable efforts among their peers.