one-way splits as symbolic transit

 Now and then I see a professional study of a transit line — often light rail or streetcar — that suggests that the two directions of service should be a little bit apart from each other, say on different streets, so that they "cover more area."

This is the clearest and simplest example I've seen of the conflict between symbolic transit and actual transit.  If you are creating transit for symbolic purposes — say, to give the appearance of permanent mobility so as to stimulate development, then it's certainly true that separating the two directions, so that rails and stops appear on two streets instead of one, will spread that appearance over a larger area.

However, if you care about people getting where they're going, the one-way split reduces the area served by a transit line.  That's because for a two-way line to be useful, you have to be able to walk to both directions of a service.  The further apart the two directions are, the smaller the area (light blue) that will have a reasonable walk to both of them.


One way split

If you're wondering whether a project is about getting people where they're going or just appearing to do so, the handling of one-way splits is often a clue. 

Obviously, one-way splits for transit are often required by a one-way street pattern, but even in these cases, when we're planning for both legibility and ease of use, planners sometimes suggest combining the two directions on one street.  This can be done by giving transit a lane that allows it to travel against the main traffic direction (called a contraflow lane), so that although traffic is split between two streets all transit is on one.  That maximizes the area actually covered by the line, but of course, it may reduce the area that has symbols of being covered! 

23 Responses to one-way splits as symbolic transit

  1. ant6n February 21, 2012 at 2:23 pm #

    Splits also make the system more complicated. Especially in the context of frequent service networks, it would be nice to have systems as simple as possible, such that users can navigate with only one map. In my Montreal frequent service map I tried to label if a bus goes on one street in one direction, and on another in the other direction, but it’s just cumbersome, and messes up the simplicity of it all.

  2. Jeremy Krygsman February 21, 2012 at 4:56 pm #

    Here in Waterloo Region, there are plans to build an LRT that splits in several locations: in Downtown Kitchener and Uptown Waterloo. I live Downtown right near the existing central bus terminal, which will be replaced with the southbound LRT station 450m away from my apartment (great!). But I would have to walk 5 blocks (850m) just to get to the northbound station!
    In this case though, the reasoning has more to do with space constraints in the ROWs (they want to keep bidirectional car traffic on all affected roads).
    Here’s a link to the plans:

  3. Bulbous February 21, 2012 at 5:22 pm #

    Here in Perth, Western Australia, our previous light rail plans (from 2006-ish) decided to put both lines on a couple of the one way streets in the CBD, with segregated right of way, leaving one lane of traffic and one lane of parking (down from two lanes of both in most cases). I believe it was due to this issue being raised during the planning, and they decided to move away from the couplet design on adjacent one way streets.
    I think that these plans are part of the bigger light rail plan being done now, as part of our 2031 transport plans (I think final route alignments are being worked out this year), and the route for this section remains roughly the same. The thing that did surprise me was that they were not shy about removing vehicle lanes to provide segregated right of way for the trams/LRV’s, which for a car-based city like Perth was a revelation (and something I believe should be done in quite a few corridors for both buses and light rail in Perth – most especially the new Great Eastern Highway expansion).

  4. mike0123 February 21, 2012 at 7:17 pm #

    I’m curious how you feel about one-way splits to create loops near the ends of routes that exist primarily to provide coverage to low-density areas.
    I guess the answer depends on the length and width of the split loop, and the frequency of the route. If the headways are longer than the time to complete the loop, it’s probably better for buses to go only one way around the loop.
    Are low-frequency coverage routes symbolic transit, split or not?

  5. LA Streetcar February 21, 2012 at 10:59 pm #

    The LA Streetcar was going to have one of these “symbolic” splits that would have significantly reduced the utility to riders. Fortunately, the termination of the redevelopment agencies statewide probably has placed the project on hold for the time being, since that would have been a major source of funding and financing.

  6. francis February 21, 2012 at 11:42 pm #

    One case a split may be useful: the block between the lines generates the bulk of the ridership. In this case, the split allows riders from that block to go both ways without crossing the street.

  7. Eric February 22, 2012 at 2:59 am #


  8. Jarrett at February 22, 2012 at 3:51 am #

    Mike.  One way loops at line-ends in low-density areas are often a way of providing basic coverage at minimal cost.  These are designed for an actual transit purpose, so I would not call them symbolic.

  9. kantor February 22, 2012 at 5:58 am #

    Many streetcar systems in Italy, almost all sadly dismantled in the fifties and the early sixties, had split tracks (and often big loops). The main reason was that in many italian cities the streets are narrow and the blocks are short, often a mere 100 meters of width. So running two one-way tracks in parallel streets was not terribly disrupting.
    However even then that was perceived as a severe limitation and was often used as an excuse to “modernize” (i.e. to destroy) the system.
    Admittedly in some cases going to buses was an improvement, at least for a while. There are several exceptions however and the main one is
    Genoa (that Jarrett saw only at night :)); it is a very interesting case of absolute mismanagement of resources worth exploring, but I do not want to bore the good folks here, so I’ll say only a couple of things. Genoa has 610.000 inhabitants (less than in 1936); in the fifties it ballooned up till 800.000 and had a transport system (mainly trams and trolleys) that could move a lot of people around. Now, despite a (small) new subway it is an absolute transportation nightmare; maybe the worst city in Italy from that point of view.

  10. Bossi February 22, 2012 at 7:03 am #

    Just a thought… I’d actually be alright if I was riding a split route where my home &/or are located along my AM path but I had to walk an extra distance for the PM path. In the AM I’m usually rather less-sociable and more keen on just getting from point A to point B. In the PM I’m often more willing to wander about, get a nice walk, stop somewhere for dinner or groceries, etc.
    Of course, there’s the other half of people living/working on the PM route or those who are morning people…

  11. Alan Robinson February 22, 2012 at 8:43 am #

    What motivations could there be for splitting lines. I can think of the following:
    – Making it simpler to turn busses around without a dedicated loop.
    – To match a one-way street pattern
    – To fit narrow steets.
    – To preserve parking on one side of a street.
    – To give the false impression of coverage.
    – To give an impression of importance to the area within the split.
    – To avoid placing transit stops on the side of a street devoid of demand (for instance, on a street along a river. @Eric, this can be an edge problem not a corner problem.)
    It surprises me when reading this list how many of these pressure are exacerbated in downtown cores, where a line’s coverage has the ability to serve the most people.
    @ Bossi,

    Of course, there’s the other half of people living/working on the PM route or those who are morning people…

    … seems like a new variable for TransitScore.

  12. Chaz February 22, 2012 at 9:26 am #

    The same geometric principle also applies to stop spacing, and highlights the importance of closely placed stop pairs, one for each direction of travel.
    I’ve encountered several times where someone wants to put the sister stop nearly 1/4 mile walk away from it’s sibling.

  13. ant6n February 22, 2012 at 1:56 pm #

    Also, single directional stops again make the system more complicated; and hard to represent in a concise way.

  14. Jarrett at February 22, 2012 at 5:18 pm #

    Bossi.  While everyone has preferences such as the one you express here, a transit system designed around such micro detail would be a nightmare of complexity.  Cheers, J

  15. Andrew February 24, 2012 at 6:52 am #

    The post is misleading. It makes more sense to calculate the round-trip walking distance, in which case the areas covered in blue would be the same.

  16. James February 24, 2012 at 7:42 pm #

    Jane Jacobs addresses this problem in chapter 18 of Death and Life of Great American Cities, noting that bus ridership dropped in Manhattan on avenues that were changed from two way to one way traffic. Page 351 of the 1992 Vintage paperback edition, indexed under “one-way streets.”
    Moving from two way to one way street traffic is a measure that trades off transit rider convenience for increased vehicular traffic throughput. Why you’d want to design your neighborhood’s traffic patterns to encourage people to use your streets as a thoroughfare at the expense of making it harder for people to actual get to places in your neighborhood, though, is beyond me.

  17. david vartanoff February 25, 2012 at 11:00 am #

    Good point, Jarrett. And of course one way streets were an excuse for bustitution of streetcars.

  18. hezec February 29, 2012 at 2:54 pm #

    Not the same, just less reduced. For instance, on the right end of the image your idea would cause a roundtrip of 400m+800m=1200m compared to 400m+400m=800m on the bi-directional section. 200m+600m would work, though.

  19. hezec March 1, 2012 at 12:15 am #

    …and of course the same applies on the other side, which just goes to show I didn’t think my previous comment far enough. The area is equal but displaced from the original. My bad. Many people likely won’t be quite as rational, though, as is now being argued in the newer post’s comments. Over and out.

  20. Nathanael Nerode March 1, 2012 at 1:16 pm #

    I’d like to point out that one-way street grids are now considered to be hostile to lively street life and local *car* access.
    I don’t think one *ought* to be constrained by a one-way street grid. One-way streets are a policy choice, and it’s looking more and more like they’re usually a bad one.

  21. Nathanael Nerode March 1, 2012 at 1:17 pm #

    Really narrow streets are an exception of course; there, going one-way is pretty much required by lack of room for two lanes.

  22. Neil D March 6, 2012 at 8:54 am #

    The problem with considering round-trip walk distances is that you disadvantage those with a moderate degree of mobility impairment. They might be able to (just about) make a walk of 400m, but one of 600m might put them off making the journey. That their return walk might only be 200m is irrelevant to them. This might increase call on flexibly-routed services or just lead to the journey being abandoned altogether and hence reduce patronage. Mobility impairment doesn’t have to be a disability – it can be carrying heavy shopping bags, or awkward topography, or barriers to movement such as having to cross yet another four lane road to get to your stop.
    For simplicity I stick with Jarrett’s original definition – with a one-way street pattern it’s easier to demonstrate the need for contraflow bus lanes on the basis of maintaining overall access to a service, than it is having to sell a split loop to the public.

  23. Aleks November 19, 2012 at 9:30 pm #

    Francis and Alan: The benefits you describe would require an inverted couplet. Otherwise, people on that block would have to cross the street in both directions.
    Inverted couplets definitely have their place. For example, a pair of inverted couplets can create a highly-active civic square. But I doubt that anyone proposing “symbolic transit” is going to suggest something as radical as an inverted couplet.
    Bossi and Jarrett: One preference that virtually everyone shares is that walking downhill is better than walking uphill. In Seattle, Route 47 serves a primarily residential district in the west part of Capitol Hill. Most of the passengers are heading downtown in the morning, and heading home in the evening. The bus happens to use a couplet, where the outbound street is significantly higher elevation than the inbound street. Therefore, people walk downhill to the bus in the morning, and the bus drops them uphill in the evening. I’m not sure I would have designed the system this way, but given that we have it, it’s actually pretty convenient.

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