This post is an important early section in the book I'm working on. Longtime readers will recognize the primordial muck from which it arose. I thought I would share it because it's a key conceptual marking-point and I know it will be controversial. In brief, I argue that while "mobility" is problematic as a goal of a whole transportation system, we can't abandon it as a descriptor of transit's primary purpose and function, because to do so makes it impossible to understand how and why transit does what it does. If anyone has a better word for what I'm calling mobility, I'd love to hear it.
Because transit debates so often lose track of transit’s defining product – which I’ve called personal mobility – it’s worth pausing to clear some weeds around this concept.
In contemporary urbanist thinking, the world mobility is profoundly out of fashion. Todd Litman of the Victoria Transport Policy Institute defines mobility this way:
Mobility refers to the movement of people or goods. It assumes that “travel” means person- or ton-miles, “trip” means person- or freight-vehicle trip. It assumes that any increase in travel mileage or speed benefits society. (Litman, 2008)
By this definition the output of transit that matters is passenger-miles or passenger-km. A passenger-mile is one passenger carried for one mile. (Ten passenger miles, for example, could mean one passenger carried for ten miles or ten passengers each carried for one mile.)
Defined this way, the concept of mobility can be misleading because it doesn’t measure how readily people got to where they were going; it just measures how far they were moved. Most of the time, though, our travel isn’t motivated by a sheer desire for movement; it’s motivated by the need to do something – make some kind of economic or personal contact – that is too far away to walk to.
Suppose that your favorite grocery store is reachable from your house only via a circuitous bus route. When you ride this bus to the store, you only want to go about 3 miles, but the bus takes you 5 miles in the course of getting there, and the bus company will claim to have delivered 5 passenger-miles of mobility as a result of your trip. Obviously, that’s unfair, because you only wanted to go 3 miles.
But really, you didn’t even want that. What you wanted was your favorite grocery store. You wanted access to your grocery store, not 3 miles worth of mobility.
So there are two problems with mobility, defined and measured this way. First, it measures how far you were moved, even if some of that movement wasn’t necessary. Second, more fundamentally, it implies that a greater good was delivered by taking you to shops three miles away than would have been delivered if the same shops were close enough to walk to.
Transit that participates in reshaping the city, by encouraging greater density and walkability so that the basic needs of life are available with less travel, has the effect of increasing access even as it reduces our need for mobility. From the perspective of almost all of transit’s goals, replacing long trips with short trips that achieve the same outcome is a good thing. If shops identical to the ones you have three miles away were to open next to your house, you wouldn’t travel as far. In fact, you wouldn’t make a transit trip at all. The bus company would lose a customer and its ridership would fall as a result. Yet clearly, the ability to do something via a short trip rather than a long trip is better for you, better for the energy-efficiency in your city, and better for the environment.
That’s why Litman suggests we should care more about what he calls access:
Accessibility (or just access) refers to the ability to reach desired goods, services, activities and destinations … Access is the ultimate goal of most transportation, except a small portion of travel in which movement is an end in itself (jogging, horseback riding, pleasure drives), with no destination. This perspective assumes that there may be many ways of improving transportation, including improved mobility, improved land use accessibility (which reduce the distance between destinations), or improved mobility substitutes such as telecommunications or delivery services. (Litman, 2008)
Mobility is how far you can go in a given time. Access is how many useful or valuable things you can do. If a new grocery store opens near your house, that doesn't improve your mobility but it does improve your access. You can now get your groceries closer to home, so you don't need as much mobility as you did before. You can also improve your access by working at home instead of commuting, downloading music instead of going to a CD store, and moving in with your romantic partner. In other words, a lot of the work of access is simply about eliminating the need to move your body around the city in order to complete the economic and personal transactions that make up a happy life.
But before we dismiss mobility as a distraction, let’s look again at the three ways of improving access, as Litman lists them:
- “Improved mobility”
- “Improved land use accessibility (which reduces the distance between destinations)”
- “improved mobility substitutes such as telecommunications or delivery services”
When I say that transit’s product is personal mobility, I’m emphasizing the first of these three ways of improving access. I’m not implying that the others are unimportant, only that the first of these – improving access by improving mobility – is transit’s primary job, just as firefighting is the fire company’s primary job.
Transit does have side effects, though, that affect the second kind of access, and we’ll return to these in Part II. If an especially popular or exciting form of transit, such a streetcar or monorail, is built in an area, this may raise the land value of the area in a way that encourages denser development, and denser development often improves access by putting shops and other destinations that you value closer to your house.
Designing transit to trigger desirable development is one of the core ideas of the New Urbanism, but like many new ideas it’s really an old one. In 1900, when public transit was the primary form of urban transport for distances too far to walk, the public transit infrastructure determined the shape of the city’s growth. In fact, many transit lines were created and owned by developers whose real goal was to build and sell houses along the line.
So transit can improve access two ways: (a) by providing personal mobility and (b) by influencing development to create denser communities where less mobility is required to do the same things.
The second of these, however, is obviously an indirect impact. Transit may lead to access-improving development, but only via several intermediate and unreliable steps. You can build a rapid transit line and still not get more density if several other things don’t fall into place – including zoning, economic growth, cooperative neighbors, and bankers willing to lend to developers. In that case, the new transit project doesn’t improve access at all, unless it has improved the first kind of access: mobility.
What is more, the ability of transit to stimulate development is clearly related to how well that transit seems to promise good mobility to the people who will live, work, or play there. We don’t pay more for an apartment over a transit station because the station is a nice community amenity, like brick paving and planter boxes. A transit station adds value to development precisely because buyers think it will make it easier for them, or their tenants, to get around. So if transit isn’t credible in offering mobility, or at least appearing to do so, it’s unlikely to stimulate development.
In 2009, we began to see web-based tools that allow you to enter an address and see where you can go, in a fixed amount of time, from that address. Here, for example, is the output from WalkScore.com's travel time tool, when queried by someone near the San Francisco Civic Center at 9:00 AM:
These tools aren’t for planning a trip, they’re for visualizing your freedom. Not your freedom in some improved city of the future, but your freedom now. That’s what mobility is: your freedom to move right now.
But the genius of these tools is that they let us see how choices we might make would affect that freedom. Imagine that you’re deciding where in a city to live. For each house or apartment you’re considering, you can check one of these sites and see quickly where you’ll be able to get to easily on transit. And you won't get just an abstract "transit score." You can look at this map and see how easy it will be to get to the places that matter to you.
The tool might save you a fortune. If you’ve decided that you can only afford a house in a distant suburb, enter that address and you’ll get a clear map of just how far away things that you care about will be. You might run the numbers on the cost of commuting and decide you’ll save money by spending more to live in a better location, closer to rapid transit and/or closer to the city, where you’ll spend less on transportation.
In other words, you might make a decision that requires less mobility, because it has better access. That access will consist not just in being closer to things you value, but also in having better transit options for the trips that are still too far to walk or cycle.
Mobility and access aren’t opposites, and mobility isn’t some tired doctrine worshipped only by blinkered traffic engineers. If we want cities to be built in ways that require less travel, cities with better access, we will do that by ensuring that those cities still have generous transit mobility. We need to show that if you locate in a transit-intensive place, you will be able to get to lots of places that matter to you, on transit; indeed, that you’ll have full access to all the riches of your city, or at least those that you care about.
So in a book on transit, I’m going to insist, unfashionably, that in the transit business mobility is still our primary product. Mobility is only one dimension of access. The other two, as Litman defines them, are urban redevelopment and telecommunications, both of which can reduce the need for travel. But mobility is the kind of access that most people expect transit, in particular, to deliver.
One of the major hazards of urban planning is that planners and theorists can get so excited by their visions of the future that they lose track of the present. We can imagine futures in which transit systems help us to build denser cities, where we can have more access because things are closer. But if we want today’s voters to support our vision, we have to care equally about what their needs are right now.
In the short term, most of us are stuck with the current geography of our lives. Our homes, jobs, relatives, friends, and favorite shops are wherever they are, and we’ve accepted, consciously or not, the need to travel the distances between these important things. We can try to relocate some of these things in the months or years ahead, but we can’t relocate any of them today.
This book will look more at urban form and all the ways we can change it, but we can’t use transit to create better cities unless we first understand how transit does its primary task of providing mobility. Meanwhile, though, transit needs to focus on the shorter-term perspective: the perspective of someone who needs to go somewhere, and get there soon, to address a need that they have right now. This person isn’t thinking about how better transit might help transform her city. She’s thinking: “I just need to be there!” We need to figure out whether transit can help her, and if so, how.