Transit
Streetcar vs. bus debate hinges on mobility vs. accessibility
Advocates and policymakers constantly debate the virtues of different transit modes. Should we build streetcars or BRT? Commuter rail or heavy rail? Each involves technical and cost tradeoffs, but transit advocates often don't agree. This debate stems from a difference in how people think about transportation. Is the goal to maximize mobility, or accessibility?
Portland Streetcar. Photo by K_Gradinger.
Professionals' precise definitions vary, but in general, mobility refers to the distance or area a person can cover in a period of time. Accessibility is a more qualitative measure about what you can access, not how much ground you can cover. If a given transportation system allows you to easily access your job, a grocery store, and other local retail services within 20-25 minutes of travel time, that site would have good accessibility, even if that 20-25 minute window of time doesn't allow you to travel very far. Mobility, on the other hand, is transportation for transportation's sake. It deals only with distances and speeds, and thus, by extension, area covered.
Choosing which concept to focus on affects how land use fits into the debate. Mobility is a pure measure of distance covered, whereas accessibility is more concerned with the 'what' than the 'how far.' What's on the land matters a great deal. Increasing mobility usually also increase accessibility: the more area you can cover in a given amount of time, the more uses you can reach. But we can also increase accessibility without actually increasing mobility. In the United States, we have a legacy of designing transportation policy on mobility alone, while ignoring accessibility.
Jarrett Walker observed,
Streetcars that replace bus lines are not a mobility improvement. If you replace a bus with a streetcar on the same route, nobody will be able to get anywhere any faster than they could before. This makes streetcars quite different from most of the other transit investments being discussed today. ...New streetcars that replace buses do not change mobility. In theory, a streetcar traveling in mixed traffic will have the same mobility as a bus. Jarrett and other bloggers then grapple with mobility versus accessibility and what to measure. Cap'n Transit asks, "Why do we care about mobility?"Where a streetcar is faster or more reliable than the bus route it replaced, this is because other improvements were made at the same time
— improvements that could just as well have been made for the bus route. These improvements may have been politically packaged as part of the streetcar project, but they were logically independent, so their benefits are not really benefits of the streetcar as compared to the bus.
Interestingly, Jarrett uses Walk Score to count the places, meaning that his mobility takes density into account. That makes it more valuable than simply measuring how many route-miles you have available to you. There was some back-and-forth in the comments about whether streetcars could increase mobility by increasing density relative to a similar investment in buses, but I don't think there was a solid conclusion.Jarrett's response acknowledges the intrinsic value of accessibility, but also notes the limitations of that concept:
The argument is that the number of places you can get to doesn't matter so much. What matters is how far you need to go to do the things you need to do. In a denser and better designed city, your need for mobility should decline because more of your life's needs are closer to you. That's unquestionably true, and I suspect anyone who has chosen an urban life knows that in their bones. ...This cuts to the core of the tension between mobility and accessibility. In one sense, increasing mobility naturally increases access simply by opening up easy travel to new areas. However, accessibility captures a more complete picture by asking what the travel is for, not just to accommodate it. Streetcar systems and other rail based transit tend to have higher ridership than similar bus systems. This is known as rail bias, the tendency of passengers to ride trains more often than projected based solely on the mobility improvements of a transit line. Might this rail bias actually represent an accessibility bias?One puzzling thing about the access-not-mobility argument is that it suggests that much of what we travel for is generic and interchangeable. Many things are. I insist on living within 300m of a grocery store, dry cleaner, and several other services because I need them all the time and don't want those trips to generate much movement. But I go to a gym that's about 1500m away because I really like it, and don't like the ones that are closer. And every city worth living in is packed with unique businesses and activities and venues that must draw from the whole city. A lot of us want more of that uniqueness, less interchangability, in our cities. How is that possible if citizens aren't insisting on the freedom to go where they want?
Metro's history shows us some of the tension between these two concepts. The Orange line includes areas focused on accessibility between Rosslyn and Ballston, while the outer reaches of the line travel longer distances at higher speeds, prioritizing mobility. Of course, a subway presents an inherent increase in mobility over a bus or streetcar anyway, thanks to the grade separation of the subway tunnels. Still, the hybrid nature of Metro's system shows the different conceptions of mobility and accessibility.
In Zachary Schrag's The Great Society Subway, he concludes with a quote from a now retired WMATA official involved with the planning of Metro. Before choosing technologies, routes, and levels of transit service, you have to ask "what kind of city do you want?" One of the key arguments in favor of streetcars is their ability to attract transit oriented development in ways that buses cannot. If we accept Jarrett Walker's assertion that streetcars do not offer a mobility improvement over buses, what about an accessibility improvement? Transportation investments can be powerful forces for attracting and shaping development, and thus improving accessibility by shaping the city.
In determining what kind of city we want, we also have to recognize that different modes of transportation offer different improvements to both mobility and accessibility. Transit system can accomplish both goals, but design choices inherently emphasize mobility over accessibility or vice versa. Every fantasy transit system makes value judgments about mobility versus accessibility. When those systems are the work of one individual, they represent the preferences of that individual's vision for the city. How should the Washington region balance mobility and accessibility in future transit and transportation planning?
Cross-posted at City Block.
Alex Block is an urban planner in Washington, DC. Alex's planning interests focus on the interactions between transportation, land use, and urban design. He also blogs at City Block and currently lives in Hill East.  |
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The rail bias is simply a reflection of the fact that rail is a tool for better planning. Rail encourages denser, walkable development. This arrangement alone improves accessibility. What the author calls mobility is then negated. The need for "mobility" only makes sense in a low-density environment. In reality, people go to a destination. If the destinations are closer together, the need for "mobility" is less acute than accessibility.
Hence why streetcars always outperform buses.
by Cavan on Jul 15, 2009 1:56 pm • link • report
mobility=livability. Not being able to do errands around a busy schedule using the bus is why people drive in the first place.
by Not from MD on Jul 15, 2009 2:25 pm • link • report
We're seeing that now with the region's BRT plans. It's admittedly a rushed process, but given the circumstances, it's a nice case study in both the potential and limits of improving mobility and accessibility.
by Alex B. on Jul 15, 2009 2:28 pm • link • report
by Reid on Jul 15, 2009 2:43 pm • link • report
1. Comfort: at least the ones that ride on rails are more comfortable than buses. Less bumps.
2. Noise; much less noise pollution and much easier on everyone else in the street. Buses have moved to natural gas so they aren't quiet so dirty but they are sure more noisy. Less beeping as they don't lower themselves at every stop.
by charlie on Jul 15, 2009 2:48 pm • link • report
by Brenden N on Jul 15, 2009 2:52 pm • link • report
Some of the streetcars I saw in Europe were also quite loud (I'm thinking of Munich).
I definitely prefer streetcars to buses, but I think it's important to note that they are not inherently quieter.
by Reid on Jul 15, 2009 3:14 pm • link • report
Comfort is why people get in their car. It's easier than waiting for the bus. Comfort is also why people prefer rail over bus. It's way more comfortable.
Furthermore, I think rail shows more commitment of local authorities in that specific line. They only make that when that line is know to be heavily traveled for many years to come. Bus is more flexible. The commitment is shown in the adaptation of the area surrounding the line. Streetcars have the right of way, special lanes and get more respect from other traffic.
by Jasper on Jul 15, 2009 3:14 pm • link • report
Jarrett Walker's point, however, would be that all else being equal, streetcars do not offer a mobility upgrade over buses. That means, if you were to give streetcars dedicated ROW, you could get the same mobility from buses on dedicated ROW.
As I mentioned, accessibility, like ride quality, is a more qualitative measure than pure mobility.
by Alex B. on Jul 15, 2009 3:28 pm • link • report
This is just not true. If you have a bus but nobody is willing to ride it, then it doesn't do squat for mobility. If a bunch of new riders are willing to use the streetcar, that changes things.
Rider preference for rail is real. It cannot be simply ignored.
by BeyondDC on Jul 15, 2009 4:17 pm • link • report
Rider preference is certainly real, but that's not what mobility is looking to assess.
by Alex B. on Jul 15, 2009 4:44 pm • link • report
by BeyondDC on Jul 15, 2009 4:46 pm • link • report
by Simon on Jul 15, 2009 4:51 pm • link • report
You can see it in the current HSR debate. A lot of the debate is framed in mobility terms - how fast will these trains go, are 110 mph trains really HSR, etc. I'd say all of those discussions tend to favor the concept of mobility.
Granted, when discussing intercity travel, it's a totally different bag. But that's the point - how do you go about setting the goals for your transportation system, and therefore picking the right tools for the job? Too often, the debate is framed in simplistic terms.
Accessibility is tremendously important for urban living, and I would much rather that we favor that when planning. Still, I think there's value in getting the terms straight when having the discussion.
by Alex B. on Jul 15, 2009 4:55 pm • link • report
Generally I think streetcars are better on heavy routes but in DC we have none and spottier bus service than we need too.
But until we change the entitled, spoiled mindset where so many hop in their SUV to drive a few blocks or from one Metro stop to another, availability's not going to matter. People have to be pryed out of their SUV's with crowbars n the form of market-rate parking, elimination of free office parking, higher gas taxes, etc.
by Tom Coumaris on Jul 15, 2009 5:30 pm • link • report
In terms of semi-soft infrastructure, I would like to see some optically guided buses added to the mix. Is that a plausible addition to the BRT plans over time? A rush-hour guided bus lane (like NY has on 34th St) on some express routes could be a huge boon. As it is, during rush hour, when buses don't have to pull in and out and stop for every jerk who won't yield, I rarely see bunching and the ride is much less rocky.
by цarьchitect on Jul 15, 2009 5:57 pm • link • report
First, those terms are essentially so ambiguous as to be meaningless, and even then they'd probably only work for transit geeks, and only then to a small percentage of them. Not everyone has to know every thing, but dang -- if we want to avoid conflation, then let's get some terms that make sense to actual humans.
Second, how is the word 'accessibility' a qualitative measure of transportation? That term makes no sense if that's the accepted definition.
Third, running some junky bus line out to so far-flung neighborhood is not something we should be looking to 'achieve'. We need high quality transit -- walk, bike, train, etc. If we have existing bus service, and we don't think real transit will ever be available (for whatever reasons) in that corridor, then we should try to improve the existing service to make it less appalling. In that sense, this particular of definition of 'mobility' would be offensive to me. Being able to walk along El Camino Real, for instance (or most other ***-forsaken roads in this country), should not count towards either mobility or accessibility -- no human should have to put up with that, even if it is technically possible to survive the adventure.
There is every reason to believe that streetcars/trams can and should once again go out into the suburbs of every city/town.
Let's run a streetcar through Georgetown, up Wisconsin, out to wherever. Streetcars don't have to be these cutesy things running 2.5 mi loops in downtown -- they can actually be useful.
And let's make all bus travel in DC free starting today. Nobody should have to pay for traveling by bus.
by Peter Smith on Jul 15, 2009 6:46 pm • link • report
"Also, the buses that stop in front of my apartment are really crummy and I rarely see other people like myself ride those buses."
Let me be provocative because no one else is and I'd really like to challenge people. Some people want streetcar over bus because they think white people will use streetcars and they won't use buses.
I am convinced that this is what's really behind the streetcar movement on Columbia Pike. The PikeRide system (Metro 16s, etc.) works just fine. Also, in terms of redevelopment, the Pike is doing *just fine* anyway at least as far west as Glebe Road. But I think some people believe there's a redevelopment ceiling if bus is the only option.
So -- anyone have any data on it? Anyone agree with my take on what public officials might be thinking? Are you white and unwilling to take the bus, or less likely for reasons that you find yourself unwilling to verbalize?
by D on Jul 15, 2009 9:16 pm • link • report
You are right. We should not loose ourselves here in well-intended, but somewhat stringently defined terms. It is about reality. Not about the perfect model that simulates reality closely. Modelers (and theoreticians) tend to forget that.
by Jasper on Jul 15, 2009 9:25 pm • link • report
i'd love to hear from one single person who has a choice, but still chooses to ride Transmilenio. most people down there were already riding buses -- they ride the transmilenio buses because they like having a job, and consequently, a house, eating, etc.
also, many people are forced to ride on those big jalopies because the government restricts car driving into the city on alternate days -- this was stated in the last NYT article, but it even slipped by me -- all I saw and read was "Big Shiny Buses Will Solve World's Problems!":
To the dismay of car owners, Bogotá removed one-third of its street parking to make room for TransMilenio and imposed alternate-day driving restrictions determined by license plate numbers, forcing car owners onto the system.
There was very little context to the article. I'm all for auto restrictions, but I'd like to have seen a mention about the continuing rise in car ownership in Bogota, how people who live right next to the system will still drive their cars, etc.
by Peter Smith on Jul 15, 2009 9:48 pm • link • report
From my take, although the Pike Ride is a vast improvement in service, I still would prefer to see streetcars along the Pike as it would attract even more TOD and streetcars would attract new riders. Unfortunately buses get a bad rep for transporting individuals that are usually transit dependent, and unfortunately that is the reality in a lot of areas of the county including the Pike. I know many others that would never take a bus but if there were other options such as light rail or streetcar, they would be more inclined to use transit. Sometimes perception plays a big and major role in changing the travel patterns of others.
by Arlington Resident on Jul 16, 2009 3:48 pm • link • report
I used the Walkscore map as a definition of mobility because itÂ’s a convenient way for people to visualize their own mobility (or accessibility if you prefer). I certainly never intended this to be read as implying that I give equal weight to each square mile of area. The point is that people can look at the Walkscore map and quickly see how easy it is to get to places and people that matter to them.
The problem with appealing to accessibility is that it conflates two effects that we really have to keep separate. Many responses to my post emphasized that people would get better accessibility because the streetcar would attract development that made their city denser, so that more things would be in walking distance. We can argue about whether you need streetcars as opposed to just good transit to achieve that outcome; streetcars seem to have good effects in this regard now, but this is just an echo of current rail bias in the population and I expect it will diminish as (a) more people get smarter about transit and (b) bus technologies continue to improve in the direction of rail.
I do think itÂ’s crucial to be able to assess the ability of transit proposals to actually help people get where they are going NOW, and intended my definition of mobility to appeal narrowly to this direct effect as distinct from indirect effects such as densification that might follow, and that might turn out to have required the streetcar. IÂ’m not saying that the indirect effect is unimportant, but merely that it is less direct, depends on more catalysts and background conditions, and is therefore inherently less certain, especially when thinking long term.
Perhaps I should claim the mantle of "accessibility" for what I've been calling mobility. But I do think we have to be able to talk about direct vs indirect effects, and that there's reason to wonder how many direct benefits we should sacrifice for the sake of indirect ones.
by Jarrett at HumanTransit.org on Jul 22, 2009 11:47 am • link • report
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