# Do Complex Networks Require Complex Maps?

In his guest post, Aaron Priven explained the design process that he led for the distinctive AC Transit network map in 2003.  Here are some pieces of that map.  (For the whole thing in its most recent version, see here for PDF, or here in a version that you can pan and zoom online.)

Aaron writes:

One basic principle we wanted to follow was that there should be a one-to-one correspondence between the ink lines and the bus lines. Many American maps are like the Seattle map [pictured here] where no matter how many bus lines are on a street, they are shown by a single ink line. Trying to understand where a single line goes is very difficult on these maps. One has to hunt around for the bubbles to figure out where the route is going, and sometimes this can be very obscure.

For example …  there is a Line 30 bubble on Dexter Ave N., and another one further west, on an unlabeled street near Queen Anne Ave. N. How does Line 30 get between the two places? Does it dip downtown and come back in a U, or does it travel on one of the two sets of east-west streets shown? Or does it do something else entirely?

We wanted to make it easy to figure out how to follow where a bus line goes, which we thought was a basic goal of any bus map.

No argument there.  But here’s the AC Transit map’s legend:

Note that there is no attempt at frequency mapping here: a line that runs every 10 minutes can look just like a line that runs every hour.  Instead, they’ve used multiple colors mainly just to help people sort the lines out.

Then, to help distinguish between levels of service, they use a range of different kinds of “bubble” symbols.  But they are focused on explaining span — when service starts and ends — rather than frequency.  Is that the right priority?  Consider this:  If you tallied every person who looked at this map to figure out a particular route, what percentage do you think care that the last trip of the day is midnight or later?  Now, what percentage do you think care if there’s service on the line in the next half-hour?

Frequency usually tracks with span:  Lines that have the longest span are usually major lines in other respects, such as frequency.  But as Aaron notes, that’s not always the case, and the AC Transit system is particularly full of complexity.  So the design of this map really comes down to a choice:  Are we trying to accurately portray the complexity of the system or are we trying to help people see, amid this complexity, the portion of the network that they’re likely to find useful?

Aaron states his view clearly enough:

Ultimately, the question behind all of this is how to show the complexity of our system. In an ideal world we might simplify the system itself, but this wasn’t a choice open to us in the map project. We chose to try to capture the complexity of the system in the map rather than hide it away by creating something simpler, since we felt this would mislead potential riders. It is a disservice to passengers to portray the system as other than it is.

I disagree.  Emphasizing complexity conveys the message that the service takes a lot of work to figure out, so it tends to encourage people to consider transit only for one or two trips that they’ve learned how to make.  In fact, despite all the complexity on this map, a large share of the agency’s service, and ridership, is on a few major lines.  On these lines, the next bus is always coming soon; if you want to travel anywhere on those major lines — which together serve most of the major destinations and a lot of the residential density — the system that you need is really simple.

On the AC Transit map that simplicity is largely concealed.  The map forces everyone to wade through the complexity, even if the information they need is simple.  Even though a large share of customers, perhaps even a majority, are after fairly simple information: Which of these lines is likely to be there when I need it?  Span (when the service runs) is an important part of that, but the distinction between 10 minute frequency and 60 minute frequency affects a lot more people.  The one span category that I do recommend highlighting is peak-only, because peak-only routes exist for such a short period that showing them prominently on the map makes it harder to see the all-day structure, which is the network you’ll need to care about if you’re going to rely on transit for a range of trips.

Don’t miss the comment thread on Aaron’s post, which debates this issue in some detail.

### 16 Responses to Do Complex Networks Require Complex Maps?

1. ant6n September 6, 2010 at 12:45 am #

It seems to me that the easiest way to deal with spans would be to simply add a second legend listing all lines with number, name and service span. Like
this, only more complex. Then one could reserve the line patterns (color, thickness etc.) to show all-day frequent lines or corridors.
((The more I look at this map, I find myself lucky that the Montreal stm simplified the system just as I made a map. So just picking the frequent service it was fairly straightforward to create an abstract and compact letter-sized representation.))

2. rhywun September 6, 2010 at 5:50 am #

I completely agree with Jarrett, and I was in fact a little taken aback when Aaron suggested one of the reasons his map was so complex was to teach the agency a lesson that the system is too complex! Talk about losing focus.

3. Zoltán September 6, 2010 at 8:21 am #

@ant6n
Yet they still can’t quite bear to create a frequent Sherbrooke line, one of the most obvious possibilities of a simple Montreal bus network, by merging the 24 and 105, with a short diversion (about 500m) to serve Vendôme.
As for points on Décarie, the resources used to provide the frequent 24 could either provide a frequent shuttle from Vendôme to Villa Maria Metro, or more usefully could enhance frequency on the 17 running all the way via Décarie, with the 102 running all the way via Girouard.

4. Zoltán September 6, 2010 at 9:56 am #

Representing the span of service may not in itself be a bad thing, if you consolidate into sensible groups.
For example, for this map, you could have one symbol, the plain square. Then firstly, a category of buses that don’t run into the evening (finishes about 6pm or about 7pm). Secondly, a category of buses that run into the evening (finish later than that – 10pm, 11pm or midnight), which would perhaps be underlined, given bold numbers, or have a thick black border. Finally, buses that run all night, which would already be formatted as buses that run into the evening, would be given a crescent moon symbol next to the number.
Alternatively, you could do as Kick Design’s New York Subway map, and have a separate evening and late night map (day/http://i51.tinypic.com/34yoc39.png>day/ href=night),”>http://i52.tinypic.com/34yv6ls.png>night), which has the benefit of a de-cluttered view of services relevant to passengers travelling in the evening. In that case you could label buses all the same in the daytime map, and on the late evening map show all the buses running into the evening, with the underlining/bold numbers/border etc. for buses running until midnight, and that crescent moon symbol for those buses that run all night.

5. Zoltán September 6, 2010 at 9:58 am #

http://i51.tinypic.com/34yoc39.png
http://i52.tinypic.com/34yv6ls.png

6. Pete (UK) September 6, 2010 at 10:15 am #

When I looked at this map I was immediately put off by the complexity of all the sybols used to represent service variations to the extent that I just couldn’t take it all in – a case of ‘too much information’. For an Agency’s websie map you could use more interactive features to show the detail where it is relevant. Here is an example of clarity – Tahesdown Transport’s map in the town of Swindon, England. There is an interactive route diagram. Click on a route and the service span (daytime, eveining, Sunday), frequency, and termini are displayed in a box. Click on the box to go to the timetable.
http://www.thamesdown-transport.co.uk/index.asp?m=205&t=Where+do+we+go%3F
For more detail a PDF showing the routes on a street map, with all bus stops indicated is also available, listed under ‘Other Maps’

7. Pete (UK) September 6, 2010 at 10:18 am #

I’m going to type that again, a combination of mild keyboard dyslexia I’m afraid!
When I looked at this map I was immediately put off by the complexity of all the symbols used to represent service variations to the extent that I just couldn’t take it all in – a case of ‘too much information’. For an Agency’s website map you could use more interactive features to show the detail where it is relevant. Here is an example of clarity – Thamesdown Transport’s map in the town of Swindon, England. There is an interactive route diagram. Click on a route and the service span (daytime, evening, Sunday), frequency, and termini are displayed in a box. Click on the box to go to the timetable.
http://www.thamesdown-transport.co.uk/index.asp?m=205&t=Where+do+we+go%3F
For more detail a PDF showing the routes on a street map, with all bus stops indicated is also available, listed under ‘Other Maps’

8. Eric Doherty September 6, 2010 at 10:46 am #

I think that in most networks there are only a few places where such a map would be very useful. I would like to have one for the downtown core of Vancouver BC, but it would not add that much for most of the network.
You really need lots of maps, I have missed connections because I could not find the bus stop at a ‘bus loop’ where the loop and surrounding streets are full of different stops. Bay 11 is off on a side street because there are only 8 bays in the loop. And when I get off at a station, I really want a map that shows every street and but line in the immediate area.
But the frequent service network should be the map you see most often.

9. ant6n September 6, 2010 at 1:26 pm #

@Eric
Bus loops at the end of liens are really annoying, especially the large ones. At these, an abstract/compact map will diverge from reality, because it’s hard to represent them. This also means that users will find them hard to understand as well. And they make for a bad network, because lines will not meet each other at some defined intersection.
I understand the need to get buses to turn around at the end of a line, but couldn’t that happen outside of the line, just after the terminal stop? Would that take too many resources?

10. Zef Wagner September 6, 2010 at 2:33 pm #

Transit agencies need to get over the idea that they should have one single comprehensive transit map. People are accustomed to using different maps for different purposes–a highway map is different from a city road map, for example. Transit agencies should focus on creating maps for target customers. The frequent network map would cater to people who use transit often in their daily lives, the peak-only map would cater to transit commuters, and the late-night map would cater to that minority who would find it useful. For local service it would be more useful to have neighborhood transit maps, showing local and frequent service for a particular area. What’s great about these various maps is that you can easily combine them online in the form of layers to be turned on and off.

11. rhywun September 6, 2010 at 7:42 pm #

I’m not so sure how keen I am on the idea of multiple maps… Even with the “frequent map” which has been such a popular topic lately, I think I would actually prefer high frequency to be indicated on the MAIN map rather than on a separate map, if it’s done well. That might be my own bias though, because I like to stare at a map to see all the possibilities of where I CAN go, not just where there are (say) high-frequency or night routes. As long as I can easily discern WHICH routes are high-frequency, I’d rather see all routes at once.

12. Paul K. McGregor September 6, 2010 at 8:05 pm #

I agree that the complexity of the map does mask the simplisty of the system. I also agree that showing frequency is more important than span of service except for those peak/off peak service. When I used the map, I didn’t even pay attention to those bubbles because of the complexity and also in part because it was information that I never really paid attention to.
One thing I would add is that the Rapid routes are not really called out clearly to distinguish them from the other local routes that run in the same corridor. So you really can’t tell where the Rapid route operate.
We seem to be having a lot of discussion about this topic but when it’s all said and done, it is really what the customer would want on the map, not what the planners or map makers or transit geeks think it should be. I was wondering if anyone out there has really done any kind focus groups or market research to find out what kinds of things are important to customers to show on a map?

13. Zef Wagner September 6, 2010 at 8:23 pm #

Rhywun, you do have a point. I think multiple maps would work fine for most people, but a comprehensive map could work as long as rapid and frequent routes are most prominent.
I like the scheme mentioned on this blog before where locals are narrow lines, frequent routes are thick lines, and express routes are dashed. Rapid routes would have to be delineated some other way.
We should think about the use of color, as well. I find the dizzying array of colors on most transit maps to be confusing because they don’t mean anything. They just make the system look more complex. I would say use colors only on the major rapid routes, like subway lines in NYC, then make bus lines all the same color, but vary the thickness as mentioned above. Also, people, please be sensitive to the 10% of male population who have some degree of red-green colorblindness. Don’t put red and green close to one another, and add some blue tint to one of them to set them apart.

14. francis September 7, 2010 at 10:02 am #

Good point on the colorblindness – in the earlier post it was mentioned that AC Transit used color LED signs to display route numbers (hence the rainbow of colors on the map) but couldn’t use red since the police felt it could be confused for a taillight. But no restriction was made for green!

15. Wai Yip Tung September 7, 2010 at 5:26 pm #

This is a one size fit all problem. You want one system map that show all the lines. You want it to reflect the complexity of the system. You want it to be useful as a street map. You want it to be user friendly. And you want to print all these on a single sheet of paper.
Luckily we are living in a new era when maps can be generated on demand online. Many people are comfortable to check online maps and use it to find driving or transit direction. Also these days the route and time table are often published in machine readable GTFS format. This make it easy for professional outside of the official agency to make their own map, like the kick map of New York.
Even though it is not practical to use a computer all the time, and mobile phone is still has a lot of limitation, I see electronic map to be a big part of the future. One size fit all paper map is not going to be too helpful for people to navigate the system.

16. ajedrez November 20, 2010 at 1:44 pm #

Here in NYC, I think we have a fairly good system for showing the system. For example, here is the Queens Bus Map:
http://mta.info/nyct/maps/busqns.pdf – It makes no references to frequency-though it does show weekday-only services.
On the back, there is a legend that shows the operating hours and frequnies of the routes at different times:
http://mta.info/nyct/maps/busqns2.pdf