Wednesday, November 5, 2014

How I Learned to Stop Worrying and Love the Last Mile Problem

Heard of the last mile problem? The last mile problem is a feature of rapid transit, which tends to be expensive and have widely spaced stops, which means that in most cities where rapid transit exists, there will be few areas within easy walking distance of the rapid transit stops. There is then the issue of the last mile of the trip which cannot be done on the rapid transit line but must take some other mode of transport.
The last mile problem: Going from A to B, B is too far from the rapid transit line to be walked to comfortably, needing a modal change
The typical solutions to the last mile problem tend to about trying to accommodate this modal change by making it easier to get to and from the station.

For instance, on commuter rail lines, it is frequent in North America to see huge parking lots right next to the station so that suburban residents can park there and take the train downtown. That way, the "last mile" from low density suburban neighborhoods to the train station is done in a car.
Big park-and-ride lot next to commuter rail station in Blainville, a Montréal suburb (you can see the train at the bottom left)
More frequently, this is done with feeder buses that go around neighborhoods to provide service to plenty of people and take them directly to rapid transit stations:
A bus terminal at Angrignon Station on the Montréal subway
More rarely in North America but common in Japan and the Netherlands is to provide for plenty of bicycle parking so that residents around stations can go there on their bikes.
A 4-story high bike parking garage near Chigasaki station, in the Tokyo area
An advantage I will grant BRT is the ability to offer a "trunk-and-branch" system where buses on the trunk bus lane get off at "stations" and then act like feeder buses. That way, it reduces transfers. However, such a system may be good during peak hours, but less during off-peak hour as the frequency required on each branch may not be the frequency required on the trunk, forcing the transit authority to either run plenty of mostly empty buses on the trunk line (poor vehicle utilization means high operating costs) or reduce frequencies on each route to the point of discouraging taking the bus.
A trunk and branch BRT system with bus routes having "feeder" routes to increase coverage and continuing down the "trunk" of the BRT along a few stations
But let me ask a question here: is the last mile issue really a problem... or is it in reality an opportunity?

The last mile as an opportunity rather than a problem

A few posts back I wrote about what attracted industrial parks and shopping centers to highway interchanges. I said that people who decide where to settle care about a few things:
  1. The catchment area of the location: how many people can reach the place in a short amount of time
  2. The local traffic already present, which is useful to attract attention from passer-bys for whom the marginal cost of going at the location is nearly nil as it's already on the way.
  3. The transport capacity of the network leading to that location, as congested transport links can discourage people from going there
These factors explained why businesses went to highway interchanges when available, the location at highway exits allowed them to maximize the catchment area as plenty of people would be within a short drive from it, thanks to the high speed of highways. As there are only a few exits on highways, it means that there is plenty of local traffic passing through at each interchange, even as highways drain traffic off of commercial streets around. Finally, highways tend to have relatively high capacity per lane.

We can find a nearly perfect analogy here between rapid transit lines and highways... like highways, rapid transit lines are high-speed, high-capacity transport links with limited entry points and exits. Consequently, they draw people to them as people seek to profit from their speed (for transit, speed includes high frequencies which reduce wait times), leading to high concentrations of local traffic at entry and exit points of the line. The speed also allows them to reach a larger area than comparable, slower forms of transport for a given travel time.

Therefore, just like highway interchanges, rapid transit stations are perfect for commercial development. They also satisfy the three criteria of high catchment areas, plenty of local traffic as people get off the rapid transit vehicles then become pedestrians (perfect passersby) and the capacity of the link is incredibly high.

So I realize that: high-density transit-oriented development that concentrates retail, services and jobs at transit stations is the single best solution to the last mile issue.

In fact, the concentration of pedestrians at stations during the modal transfers represents a golden opportunity by creating the conditions for viable high-density, pedestrian-oriented development.

When people want to build pedestrianized areas, there is always the issue of finding places where pedestrian traffic is high enough to support pedestrianization and the retail that one seeks to plan there. Rapid transit actually solves that issue, stations are perfect places to build human-oriented developments because they already represent a waystation to thousands, sometimes tens of thousands, of people each day. This is perfect for specialized stores that require large customer pools to survive. For instance, in Japan, equivalents of Wal-Mart (Ito Yokado and Seiyu stores) and Best Buy (Yamada, Bic Camera, etc...), tend to congregate around train stations. There are some built like American big boxes farther away, but others are built in compact urban forms around train station. These stores require being accessible to plenty of people to survive, and train stations, which are accessible by vast numbers of people and at the center of most local bus lines (that act as feeders to the train station), are perfect locations for them.
Movement patterns in a city with a grid-like street and transit-system, with traffic being spread around and converging on the center of the city, with proximity stores (orange dots) spread around the city and high-density activity centers (red dots) only in the center

With a rapid transit line (in red), movement patterns are shifted to concentrate at stations where high-density activity centers can start growing, which draws even more trips towards the stations, even when there is no intent to actually take the rapid transit line

In other words, the concentration of activity at a few stations, which is the result of the "last mile problem", allows for the creation of a small pedestrianized downtown area at the station itself if developments are allowed and encouraged. This is also good for housing choice, as it allows high-density housing to be grouped near stations, without causing any congestion problem, while leaving lower-density housing further out in sleepy mostly residential areas, within a short bike or bus ride to an active, pedestrian-friendly area, rather than having a mainly uniform urban area. That way, each station can be the center of its very own urban village.

That's why, far from seeing the "last mile" issue as a problem and a strike against rapid transit, I personally see it as a great opportunity to develop cities in a transit-friendly and pedestrian-oriented way. Having plenty of people waiting around and doing modal transfers creates a perfect opportunity for the kind of large scale commercial development that draw crowds. By grouping the "destinations" of trips, the centers of economic activities, around rapid transit nodes, you also reduce, maybe even eliminate, the last mile problem. Though getting to the rapid transit network from one's home may still require a modal transfer, once arrived at the station, the vast majority of a region's jobs, shops and services are a mere train ride away as they are grouped around train stations, so no modal transfer is required, only a short walk, where people join pedestrian crowds that create opportunities for pedestrian areas.

Yes, in a way it is copying the highway-oriented development, but HOD has been tremendously successful, I think if TOD is to become more dominant, copying the pattern of the most successful pattern of development of the past 50 years is not a bad idea.


  1. Great post.

    When a city only has streetcars and buses their transit is kind of useless. They're using a 'last mile' mode (buses that stop every block) to connect the entire city - which isn't a very efficient way to get around unless you're travelling short distances that happen that lay along a route.

    Another method is to have two layers (a transit hierarchy). For example, in Melbourne there's a commuter rail network that is fast for covering large distances, while the Melbourne CBD and inner neighbourhoods have a dense tram network. You can take a train into the CBD then ride a tram through the last mile to your work.

    Alternatively - rapid transit can provide full coverage without spacing stations closer together (slowing it down.) Image if we had multiple rail lines running in parallel (half a mile apart from each other), with each line having a station every 1 mile:


    You would be guaranteed to always be within half a mile of a train station. Efficient, but expensive as you'd have to build more lines (but would it be cheaper in the long run being able to eliminate buses and streetcars completely?)

    Or, like you said, embrace the problem as a reason to build density around stations. If someone has an issue with this, they can ride a bike to the station.

    I wonder if the 'last mile' problem is largely a product of suburban planners that want to keep their car scale suburbia. Should these places even be connected to rapid transit?

    1. Indeed, local, mixed traffic buses and trams are not fast enough to be really useful, unless there is no biking infrastructure, or that biking is somehow not viable for everyone (plenty of hills and/or very cold and snowy weather, though there are ways around that), or that the city has certain sections that are a bit further out which means buses go through largely empty areas at maximum speed. But that's presuming a well-designed city, in a city designed around motorized transport, buses and trams can play a transitional role to provide some mobility along roads built for motorized transport, but that's not a well-designed city, they then represent a mitigation to a deeper problem.

      There is also a potential place for what I call semi-rapid transport, BRT and surface trams running on streets with spaced stops and their own right-of-way. They don't go all that fast, maybe around 20 km/h or so, but they are competitive with cars and can be faster than bikes. And if they are used to connect a city and its suburbs (like the stadtbahn of Karlsruhe or S-bahn of Munich), they can go much faster in the fields between the city and the suburbs.

      The "last mile" is largely a problem because transit planning and urban planning are too often cloistered activities that don't talk to each other. Transit planners do not consider the development impacts of their investments most of the time, and largely only consider the question "how do I serve the existing developments?". At least, that is my impression. And they're not all that wrong in cities under a zoning straitjacket with urban planners reluctant to touch the zoning of any existing area.

      The idea of "checkered" stations on rapid transit lines, if I may call it that way, is an interesting solution, but as you say, it requires a lot of rapid transit lines, more than most cities can build. Plus, in general you want to place your stations along big arterial streets, because that is where activities will be easier to concentrate, which means stations following a grid.

    2. Even serving existing development can be a decent start. In Ontario for instance, there's a lot of malls that have bus terminals. Some in Toronto have even had rapid transit built to them like Yorkdale, Fairview, Bayview Village and Scarborough Town Centre. The Hurontario LRT and Kitchener-Waterloo LRT would also hit up several malls. Of course they still have a lot of under-utilized land near the stations which you'd want to see developed.

      In the suburb where I grew up, there's still the feeling that parking needs to be right next to the GO station though. The plan for TOD there has mostly meant putting the parking in multi-storey garages so that it takes up less space, but it's still train station with the closest thing to it being parking (and a future square/park) and then about 100-200m further you start getting (or will get) retail, office and condos.

  2. It's taking the principles of highway-oriented development and generalizing it into network-oriented development. The convergence of people on a rapid transit station causes more services to converge there, which causes even more people to go there (not necessarily to catch the train anymore), and so on in a virtuous cycle. These forces tend to draw development inward, but there are also forces pushing against that, including people wanting more room, the cost of building things taller, zoning regulations, and, in the case of highway-oriented development, the space needed for cars.

    1. Exactly.

      As to people wanting more room, I think that is in fact the beauty of development around rapid transit lines. Yes, you have very high density around the stations, but one or two kilometers out, you can have lower density developments to satisfy people who want more room. That way, people who want lower densities don't need to exile themselves to far-flung suburbs like, say, in Paris.