Beyond Measuring Access to Destinations
with Huijun Tan
For some time, researchers and professionals have advocated for a paradigm shift in transportation that focuses on access rather than mobility, as expressed here by Todd Litman or explained in this video by Dr. Susan Handy. This recognizes that the purpose of transportation is to provide access; it is not just travel for travel’s sake. In technical jargon, transportation is a derived demand, which is a term that emphasizes that transportation responds to household and land use characteristics.
The benefit of this approach is that it de-centers the mobility strategies that have not produced healthy or sustainable outcomes—or even effectively solved mobility goals (looking at you, induced demand). Prioritizing mobility and speed, for example, has serious safety consequences. In a recent analysis of pedestrian traffic fatality hotspots, nearly all fatalities occurred on multi-lane arterials (which are designed for automobility), with 70% requiring pedestrians to cross five or more lanes.
After decades of conceptualizing and measuring accessibility*(aka access to destinations) in academia, there is growing acceptance of the idea in practice. Some version of this concept has been described as creating complete neighborhoods or as 20-minute neighborhoods. However, Paris Mayor Anne Hidalgo’s plan for the 15-minute city (also called a city of proximities) has captured international attention and generated conversation about accessibility.
Part of this conversation also includes some skepticism about the feasibility and fairness of this model, particularly for American cities with land use and transportation patterns that make it difficult to get to any destinations by walking or bicycling. Another critique is that the 15-minute city excludes people with disabilities owing in part to the economic inaccessibility of existing complete neighborhoods. Edward Glaeser argues that a 15-minute city does not provide enough economic opportunity for residents; residents need access to the entire metropolis within an hour's time.
Another factor to consider is perceived accessibility. Measuring access to destinations through objective means has been computationally difficult until relatively recently. Today, practitioners have a number of tools at their disposal. These tools typically define access as the destinations closest to residents, but do people travel to the closest grocery store, as a gravity model would suggest? Or do they choose the store with lower prices or the store with more options? What if the route to the closest destination feels unsafe because of traffic or personal security concerns?
The conceptual issue, which some of the 15-minute city critiques approach, is that measures of accessibility represent potential access to destinations. They don’t represent actual travel behavior or whether resident needs have been met. For example, planners could use typical approaches to measuring accessibility to determine whether there are any food deserts in the city. However, objectively measured accessibility doesn’t capture whether stores are affordable to residents or sell culturally relevant foods. Perhaps the problem is not a food desert, but a food mirage.
Here are some recommendations for analyzing complete neighborhoods:
The climate and health benefits of complete neighborhoods are clear—they increase opportunities for physical activity as part of daily life and reduce the need for driving, which is likely to reduce greenhouse gas emissions and air pollutants. There’s also a good chance that they will create more attractive and safer neighborhoods. Many low-income communities and communities of color have reduced access to resources owing to inequitable planning and policy decisions. Improving access to destinations should be prioritized for these communities. Planners must ensure that these existing residents benefit from improvements. Methods for analyzing the risk of displacement and case studies for preventing displacement can be found on Streetsmart’s Equity and Inclusion page.
We mustn't treat the 15-minute neighborhood (local accessibility) and access to the larger metropolis (regional accessibility) as mutually exclusive paths—we need both for climate, health, and equity.
* Unfortunately, the transportation field uses the term accessibility in two different ways: one is access to destinations, the subject here, and the other is accessibility for people with disabilities. Any efforts to improve local access to destinations should ensure that it meets the needs of people with disabilities.
Climate Change, Health, and Structural Racism
Recent record-breaking heat waves have drawn attention to the impacts of climate change on health and well being. These heat waves have proven especially dangerous in parts of the country that have not historically relied on air conditioning, resulting in emergency actions that ranged from the creation of temporary cooling shelters to school cancellations. Heat is already the leading cause of weather-related deaths and climate change is increasing the severity of the urban heat island (UHI) effect.
These heat waves also elevated the scholarship that illustrates how racist land use practices, such as redlining, have created differential health effects (see also this EPA Environmental Justice webinar on Redlining and Climate Crisis). Historically redlined neighborhoods, deemed unsafe for investment by banks because they were inhabited by people of color, have been found to have significantly higher temperatures than non-redlined neighborhoods. The higher temperatures are a function of high amounts of impervious surfaces, fewer street trees, and inadequate park access. Park-deficient neighborhoods do not benefit from the cooling effects that park vegetation brings. It also means there are fewer places to retreat from the heat, which is particularly poignant when residents do not have air conditioning. Greenspace access is also important for healthy birth outcomes. Less tree canopy coverage has been found to be associated with preterm births among Black women.
While the UHI has recently captured the public’s attention, the particular hazards resulting from the interaction of climate change and racist planning policy may differ depending on the region of the country and the location of formerly redlined neighborhoods (explore the climate change hazards of your region here and here). For example, Sacramento’s formerly redlined (“hazard”) and yellowlined (“declining”) neighborhoods face high flood risk.
Air quality is another area with differential exposure and health effects. We now know that fossil fuel air pollution is more deadly than previously realized. The Fourth National Climate Assessment outlines the climate-induced risks of increased ground-level ozone and particulate matter, with respiratory and cardiovascular effects including premature deaths, hospital and emergency room visits, aggravated asthma, and shortness of breath.
Tools and Solutions
For resources on climate change mitigation and adaption, look at the C40 Cities site for suggestions. Streetsmart’s page on Greenhouse Gas Emissions (GHG) also has transportation-specific resources, including a list of proven strategies for reducing GHG.
Trees are a critical strategy for improving urban health (increased shade, UHI reduction, reduced housing energy costs, air filtration, stormwater absorption, reduced mental stress, etc.) To help identify where trees should be planted to achieve greater heat equity, use the Tree Equity Score tool created by American Forests. A simple but elegant solution for increasing street tree canopy builds on the oft-lauded 10-minute walk to essential destinations (aka 15-minute city):
“All Charlotte households will have access to essential amenities, goods, and services within a comfortable, tree-shaded 10-minute walk, bike, or transit trip by 2040” (Charlotte’s newly adopted comprehensive plan, Streetsmart emphasis).
One possible solution for reducing air pollution and increasing public space is the Barcelona superblock. In addition to journal articles on this model, the Barcelona Institute for Global Health created a mini-graphic novel to tell the fictional story of how the Barcelona Superblock came to be, inserting air pollution’s health effects (“one third of childhood asthma cases are caused by air pollution”) into the story.
This issue picks up from our last newsletter on integrating equity into transportation, with a focus on delivering equitable outcomes. The following builds upon the first steps typically taken in a transportation process: defining the problem and identifying needs.
Goals and objectives
As discussed in the last newsletter, community engagement is essential for all steps of the process, and possibly none more so for setting goals. Goals and objectives respond in part to the needs identified in the previous step. If you’ve identified the needs of a variety of community members—not only the office commuters—then you are ready to consider how to develop goals to address these challenges. This may require developing goals for supporting essential workers’ travel needs, safe travel for disabled populations (which populations are in your study area? The needs of a blind person and someone with a mobility disability are different), and reducing vehicular pollution exposure in areas with high asthma rates.
Performance measures and evaluation criteria
It is becoming more common to adopt performance measures as part of a transportation plan or project. Performance measures can be a way to increase transparency and accountability in decision-making. Some of the most successful (i.e., meaningful, well-used) performance measures emerge from the engagement process. Rather than isolating the development of performance measures in a technical committee, consider them as an extension of the goal-setting process.
Performance measures can be used in a variety of ways, in part depending on whether the transportation effort is a plan or a project. In some cases, when performance measures are reported on an annual basis, they serve to help practitioners and decision-makers “course correct” over time. Performance measures may be used as evaluation criteria for the prioritization or selection of projects. This often requires a qualitative assessment to determine which projects are most likely to help agencies meet their goals (see this newsletter for a discussion of how evaluation could build the evidence base to improve this process).
Many cities are exploring equity performance measures and tools to help prioritize projects. For example, the Portland Bureau of Transportation developed an Equity Matrix to help prioritize investment. In the Denver Blueprint planning process, health equity was an important point of discussion and analysis. Their Neighborhood Equity Index also serves as a prioritization tool.
A final note about performance measures: they are successful when there is organizational support and capacity to measure and report them. Many transportation professionals focus on the data: Do we have the right data? At the right scale? While questions about the availability and validity of the data are important, this is not the primary barrier for making performance measures useful. Agency capacity and political will are critical.
Develop and evaluate alternatives
As practitioners develop alternatives that respond to the goals (and perhaps use performance measures to evaluate their impact), how the benefits and burdens of the transportation plan or project are distributed across geographies and populations should be evaluated. Don't forget land use and zoning as part of alternatives development; land use can significantly change travel behaviors and patterns over time. In terms of equity, consider how racist land use practices have shaped landscapes and how it affects access opportunities today.
Practitioners can use tools to quantify the health and climate benefits of transportation plans and projects. Health Impact Assessments, often focused on health equity, can be used to evaluate alternatives. For regional analysis, the Integrated Transport and Health Impact Model (ITHIM) Tool calculates the health and climate benefits of active travel. ITHIM is available in the United States through this online tool. The WHO Health Economic Assessment Tool (HEAT) can estimate the value of reduced mortality from regular walking and cycling.
The final step in this process is identifying the preferred alternative, after listening to the community, understanding their needs and goals, and evaluating who benefits from and is burdened by the transportation alternatives.