Measuring Transit Effectiveness: How Isochrones Could Be the New Standard
The Shifting Preferences of an Urban World
Support for public transit in the US has increased steadily over the years as more and more people move back into downtowns and prefer car-free lifestyles. Only a quarter of 16-year-olds had licenses in 2014, and Baby Boomers, who primarily plan to age in place, have reported being amenable to alternative modes of transportation in retirement. Parallel to these major demographic shifts, our urban centers have grown rapidly to become home to over 80 percent of Americans — where having a car is quickly becoming a luxury, not a necessity.
Yet transportation metrics in use today often reflect things that may no longer represent our values. The goal of cities is not to accommodate the automobile but to foster collaboration, creativity, and commerce. Similarly, public transit aims to move people across the city freely to any and all destinations as efficiently as possible. The goal of public transportation in cities should not be to reduce automobile congestion.
If the real goal of transit is to provide connections to the communities we serve, then we should use the best data that’s available.
Why is Transit Access the Best Measurement?
We here at Remix strongly feel that transportation metrics should reflect access. Jarrett Walker defines transit access as “how many useful or valuable things you can do in a given amount of time” by using transit. By focusing on access, cities can concentrate on connecting people to jobs, educational opportunities, recreation, and — most importantly — other people. In short, transit access captures the ultimate goal of cities: to promote collaboration, creativity, and commerce.
Today, most transit agencies measure efficacy and efficiency by reporting on ridership, passengers per mile, passenger per hour, and similar measures. By focusing on ridership, however, we are looking at today’s performance comparable to past performance. This measurement is one-sided.
What we’re still missing is effectiveness — whether the quality of our service matches the community we’re serving. How many people live within 15 minutes of a given stop? How many jobs can someone access within 30 minutes of a transit ride? These provide the qualitative framework to put ridership numbers into perspective. And if an agency is trying to evaluate why ridership numbers are declining, it provides a logical starting point for whether existing routes are making the best connections across our communities.
Capturing People Impacts with Isochrones
In terms of actually applying this kind of thinking, travel-time isochrones put people at the center of the conversation. Isochrones are visualizations that show how far a transit rider can get from a given starting point within 15, 30, 45, and 60 minutes of travel using only transit and walking. By using isochrones, we can figure out where transit exists today, at what frequencies, and understand how to invest in modes of travel that get at the heart of cities’ purposes.
Travel-Time Isochrones Are Mode-Blind
If we want to emphasize access outcomes, then mode shouldn’t matter. Frequency, stop spacing, and vehicle speed should. Despite this, there’s a persisting perception that rail transportation garners more development and more ridership than bus transportation. Granted, buses are often delayed due to traffic, which affects ridership, but that boils down to a street space issue. If buses, like rail, were allocated dedicated right of way, providing more reliability, service quality can begin to be on equal footing between modes. But instead of framing the question as bus versus rail, agencies should focus on how a transit network can foster collaboration, creativity, and commerce across their cities and regions.
Travel-time isochrones are mode-blind. They do not have a bus perception problem. Isochrones prioritize frequency, access to stop infrastructure, and service spans as a basis for measuring the quality of transit available in a given neighborhood. In order to truly measure an agency’s ability to achieve broader city goals, agencies need to ensure that connections are possible regardless of the mode. Focusing on connections reframes the question about the quality of the transit network instead of the type of modal infrastructure.
Let’s look at Jack London Square in Oakland, CA, as an example. Today, people in the area can access only small portions of Oakland and downtown San Francisco within an hour of riding BART heavy rail (image, left). Without a precise measure of transit access, local officials could feel pressure to invest in more infrastructure to and from the area, causing other underserved areas to compete for limited transit dollars.
By taking a mode-blind approach, however — that is, evaluating BART heavy rail together with the AC Transit bus system and the Alameda Ferry (image, right) — a planner could easily demonstrate that people in Jack London Square can already access nearly all of Alameda County and much of San Francisco within an hour. It’s clear that transit dollars would be better spent in areas with fewer transit options that meet thresholds of high density population and jobs — and even focus on how to connect the densest parts of neighboring jobs-rich and population-rich areas.
Cities and transit agencies need to continue to be in the business of providing quality transit. In times of looming and uncertain budgets, this can help focus agencies’ services toward cost-effective strategies.
By becoming mode-blind, we can also begin to unpack our perception of Paris, Tokyo, and New York as “true” mass transit and look to places like Bogota, Jakarta, and Curitiba, where buses are paving the way. The stigma that buses have long suffered is slowly changing, and isochrones help prioritize quality of transit — and not significance of infrastructural investment — in our everyday analysis of transit benefits.
Travel-Time Isochrones Are People-Centric
Beyond the question of quality, isochrones also allow us to ask the question of quality for whom? When answered in the context of transit access, this helps us focus on the goals of promoting collaboration, creativity, and commerce for people across the socioeconomic spectrum.
Isochrones visually represent where you live, what your options are, and what can be accessed in a reasonable amount of time given your built environment. Coupling this with how many people and jobs are within a given isochrone zone, we can easily see the potential capture of that area.
Once we understand how far a person can travel within a set amount of time, extrapolating outward, we can then begin to measure the greater benefits mobility provides and understand the transit access of whole neighborhoods. Much like the concept of a 30-minute walkable community, travel-time isochrones can highlight 30-minute transit communities.
Using this concept to support the spirit of service equity, isochrones can help ensure that low-income, minority, and other vulnerable communities have reliable transit access. By adopting transit access indices, planners and agencies can leverage visualizations to ensure connections for all groups of people to the things that are valuable to them, like grocery stores, schools, and jobs. In turn, transit-accessible communities can help to achieve broader civic goals like equity and quality of life for all.
Combatting Slipping Ridership with Transit Access Measures
The past few months have been filled with reports about declining transit ridership across America. While a drop in oil prices and the growing use of ride-hailing apps are likely playing a role, there is also anecdotal evidence that light rail expansions and bus system redesigns have helped reel in these declines. Ensuring transit networks focus on access, reliability, and quality can make strides in serving the needs of the community, which in turn is one of the best antidotes to declines in ridership.
By coupling ridership goals with access goals, transit agencies can focus on meeting the needs of riders and analyze any missing gaps in the network. Ultimately, travel-time isochrones empower planners to think about transit as freedom of mobility for people, without placing a mode-lens around the how.
