some questions on frequent network mapping

@CityBeautiful21 tweets this question about Frequent Network mapping (explained here, examples here and here):

@humantransit In a place that is improving its transit but cannot yet draw a [Frequent Service] map by your ["every 15 minutes all day, seven days a week"  requirements], how would you draw the map?

When a transit agency first sits down to do frequent network mapping, this always comes up.  Not all services are frequent over the same exact span.  Many are frequent all day but not evening or weekend.  This the the normal outcome of a history of route-by-route and hour-by-hour service analysis.

[A Frequent Network policy will gradually enhance those analysis methods by bringing your focus to (a) the entire independent network instead of each route individually and (b) the entirety of the day rather than each hour individually.  Hour-by-hour analysis of routes is especially misleading because ridership at each time of day depends on service availability another time of day; you won't use transit in either direction unless it's available in both directions at times you expect to travel, and if you're not sure when you come back, you care about the abundance and extent of the whole evening service pattern.  This is why cutting evening service — which may have low ridership when analyzed trip by trip — can damage a route's usefulness throughout the service day.]

Meanwhile, how to draw the map?

1.  Start where you are.  If your current frequent service offering is only weekdays all day, then say that.  The map will still be useful.  If you can come up with some kind of minimum evening/weekend service commitment for those route segments (every 30?) then say that as part of the definition of the frequent product.  Meanwhile, you can use your long range planning process to articulate the need for a more robust service span on the Frequent Network, over time.

2.  Consider the larger principle, which is this:  Service that is more likely to be useful to lots of people for lots of purposes, and that are designed to work together as a network, should be more visually prominent.  Service that is highly specialized to a limited market should be less visually prominent, including peak-only services and any service that runs less than once an hour (or even every 30).  It's these occasional service patterns that make transit maps unbearably complicated — a problem easily fixed by ensuring that your map shows those ephemeral route segments but that they recede visually so that the more frequent network stands out.    

It never makes sense to draw a route that runs three times a day in the same line that you'd use for service every 30 minutes all day.  The problem of such maps is the same: you weaken the meaning of a line on the map by using that line to refer to something so ephemeral and specialized, thereby implying that any line on the map may be equally ephemeral and specialized.  So use a different, weaker line for those services.

For some good examples of maps showing all routes in a network, but using this principle that more frequent routes should stand out and less frequent routes should recede, see the full network maps for Portland and Spokane, discussed further in this post.  Here's a slice of Spokane's, where the red lines are frequent and the fainter pink lines are peak-only:

Spokane slice

… and of Portland's, where a wider line is Frequent and peak-only lines are dashed with a white number bullet:

Trimet slice

Full maps here:  Spokane.  Portland.

In both examples, more broadly useful services are more visually prominent.  Peak-only services recede (a thin pink line vs a wide red one in Spokane, a dashed line in Portland) so that you can see them but won't be distracted by them when you want to see the all-day network.  Both maps also highlight the Frequent Network in different ways.  Overall, I prefer the clarity of the Spokane map, because Portland introduces much complexity by trying to differentiate every route by color.  But both are good design responses to the basic problem, which is: Show me the services that are most likely to be useful!

More on this in Chapter 7 of my book.

7 Responses to some questions on frequent network mapping

  1. Zoltán April 4, 2012 at 10:51 am #

    If you wish to describe a large city’s frequent network on a small map, a separate map may be useful. Outside of these circumstances, doing as Spokane did, and creating a legible map that makes the frequent services stand out, and intermittent service recede into the background, is the best thing to do.
    I’d argue that it should be possible and useful, particularly if using colours as well as line widths like Spokane, to highlight two frequency standards, to publicise service at decent frequencies that falls outside of the frequency definition – I’d argue for a standard of every 10 minutes in large cities, and to highlight service running every 20, or 15 and 30 minutes respectively in smaller cities.
    What happens to service in the evening and at weekends varies a whole lot, but it should be possible to look at service and work out at what time of the evening service starts to drop off, and define and publicise a frequency standard after those times of what would probably be half of the daytime frequency standard – so, every 20 minutes if your frequent network runs every 10.

  2. Alan Tanaman April 4, 2012 at 12:53 pm #

    Great advice – I wish I’d read this post 8 months ago! All the same, HT has really inspired me, and as a result I have been working to provide frequent network maps for the Tel Aviv metropolitan area (, where the first big step of a long-overdue reorganisation took place in July 2011.
    Unfortunately, the changes have been plagued with local political resistance (“We want a one journey trip”) as well as bad implementation of transfer points and a lack of network-wide information.
    Although the change was based on a flat-fare with unlimited transfers over 90 minutes, the agency neglected to provide a coherent system-wide map.
    The result has been a series of u-turns where a lot of the simplification that took place has now been undone.
    So the map, which started off as fairly simple endevour, has now become a pile of spaghetti.
    I’m working on an English-language version, which I hope to release in the next couple of weeks. However, if you are wondering what is going on there – I mix the French system of marking routes with coloured lines with the classical/British system of annotating route numbers along streets. The former is used for frequent lines (thick=better than 10 and thin=better than 20 minutes) and the latter is for less frequent lines (black=better than 30, grey=lower frequency).
    So far I have avoided the evening post 8pm, because there is simply far too much inconsistency. Some frequent routes don’t even run after 9pm, whereas some that are less frequent continue until midnight. This will probably require a separate map.

  3. Alon Levy April 6, 2012 at 10:16 am #

    Alan, I think the mixture is probably the best way to deal with the (completely unwarranted) complexity of the Tel Aviv bus system. It makes it clearer which routes really are coupled for a long way and which just run on the same street for 2 km. Way better than the official map, which doesn’t use any color differentiation and expects you to guess where each line turns.

  4. DAODAO April 8, 2012 at 8:36 am #

    One of the main problems with frequent service maps is that few routes run frequently in the evenings or public rest days, and if they do run at all then, quite often the operator is different and return/multi-journey tickets are rarely interavailable. At least there are some rail/bus services on Sundays and holidays (other than Xmas) in the UK, in contrast to the city referred to in previous comments, where there is absolutely no public transport of any kind on Friday evenings, Saturdays (before nightfall) or public holidays.

  5. Alon Levy April 8, 2012 at 4:01 pm #

    Yes, in Israel indeed the lack of weekend service is a travesty. But it’s a question of religious politics rather than of transit planning.
    Moreover, because the lack of weekend service in Tel Aviv is universal, it’s possible to draw a frequent network map based on weekday off-peak frequency. Practically any user can be expected to know that there’s no weekend service. Really, the only thing that’s worth reminding people on such map is when on Friday service ends and when on Saturday night it resumes.

  6. CHKAmerica April 9, 2012 at 1:05 pm #

    CHK America was proud to work on this project for Spokane Transit and we, too, are pleased with the results. It’s nice to see the dialog about the importance of providing easy to understand information for transit customers, especially with more complex systems. We couldn’t agree more.
    Alan, it sounds like you’ve got some unique challenges in communicating Tel Aviv’s system. Glad to hear you’re employing design principles that ultimately make it easier for the rider to gather the information quickly and easily. Please let us know if we can be of assistance. It would be an interesting project on which to collaborate with you.

  7. Nathanael April 18, 2012 at 7:58 am #

    “Show me the services that are most likely to be useful!”
    This is a really excellent way of summing up principles of map design!