Tutorial: Drawing Complex Highway Interchanges in Illustrator

This is kind of a tangent to my normal tutorials, but I had a surprising number of requests for this after I published my McKinney Avenue Trolley map, so here goes!

The first thing to note is that this is not a 100-percent accurate representation of the interchange: this trolley map is not intended to be a road map or to be used to navigate freeways. I want to communicate the idea of an interchange stack and show general connections, but I’ve left some of the fiddly detail out. However, this technique stands up pretty well to any level of detail required: it’s just a matter of how patient you are.

Let’s run through this step by step:

This just shows my base layers before any of the complex stuff starts. At the very bottom, there would be a some sort of source image template for tracing elements from (which I’m not showing to improve clarity), then the background colour layer, then two road layers. In this part of Dallas, some parts of the highways are actually lower than the surface roads, so they come first (in a layer called “Hwy Low”), then a “Streets” layer for those surface roads.

A note here on colours. I actually define separate global colours for the different types of roads I need to show on a map, so that I can easily tell them apart while working. So, as shown here, there’s yellow for freeways/highways, white for surface roads and blue for freeway ramps. When I’m done, I can simply re-edit all these global colours to achieve the final look of the map (in this case, all roads end up being white). I also define a “road edge” colour for the stroke that separates the different level of roads (black in its working mode, the same colour as the background in the final piece).

I’ve added a layer for those parts of the highways that are elevated above the surface roads, called “Hwy Up”. Once I’ve drawn the paths for the roads, I’ve copied them and sent them to the back (a quick Cmd/Ctrl-C, Cmd/Ctrl-B combo) and changed their stroke from a 6pt “highway yellow” to an 8pt “road edge” black.

Here’s the first of my clever tricks for this type of work: the top yellow line has a rounded cap end, while the lower black line has a flat cap end (these are defined in the Strokes panel). If both of them had a flat cap end, then you can often see a tiny thin sliver of black extending past the end of the yellow, especially with PDF output. It’s tricky to see with this image, but I’ve circled a deliberate example of this in “Step 2” above. If both strokes have round ends, then the black stroke extends all the way around the yellow one, which we don’t want. Having a round cap above the flat cap hides it effectively every time.

Now it’s just a matter of adding all the desired freeway ramps and overpasses, working your way up from lowest in elevation to the highest. You can do this all in one layer if you’re confident in Illustrator, or you can make separate layers for each level as you go up. I thinned my ramps down to 4pt wide, with a 6pt “road edge” stroke behind them. The outside edge of the ramp stroke needs to line up pretty precisely with the outside edge of the freeway stroke below it: this probably takes the most practice to get right on a consistent basis.

You’ll note in the images above that even though the “road edge” stroke should cross over and be visible above the highway that’s on a lower layer, it isn’t. This is my second little trick: I use an opacity mask on the strokes where required to hide parts of them from view.

If you haven’t used opacity masks in Illustrator before, then I highly encourage you to do some research and make them a part of your workflow. Basically, you draw a 100-percent black object that defines the area that you want to be masked, making sure it’s placed above the stroke in the stacking order. Then, select both the stroke and the mask object and click the “Make Mask” button in the Transparency palette (you might also have to uncheck the “Clip” check box to make things show up as you expect).

It’s certainly not as intuitive as masking in Photoshop, but it saves having to shuffle things around layers in an often futile attempt to get them behind some objects while still being in front of others. In the images above, I’ve shown the masks I’ve used for each stroke as a magenta box, just to give an idea of what’s required.

Note: You could also use the simpler Clipping Mask function to achieve the same end result, although here you have to draw a masking object that covers what you want to be visible after masking, not what you want hidden. I personally find it easier to draw a small object over the tiny part I want to hide, rather than a large object that encompasses the rest of the relevant stroke.

We could really call things done after finishing Step 5, but I wanted to give the freeway ramps and overpasses a little more dimensionality and depth. I do this by copying “road edge” strokes where they cross lower layers and then pasting them behind. I cut them using the scissors tool so that I’m only left with the pieces that are required, then I just nudge them a few points directly down the page to give the illusion of depth. These are shown in green in Step 6 above.

Now it’s just a matter of redefining the working global colours for each element to achieve the final look. For this map, that means changing all the road elements to be white, and the “road edge” colour to match the background colour. Beautiful!

Future Map: Proposed Extension to the Bakerloo Tube Line, London

Very much in TfL’s house style, even as a more geographical map. Mainly interesting because it’s a major expansion of the Tube south of the Thames, which has historically been underserved by the Underground.

If you live in London and want to have say in the routing of this line, then you should go and take TfL’s survey. More information on the project can be found here, where I also sourced this image from.

New Adobe Illustrator “Join Tool” Aids Transit Map Design!

When Adobe Illustrator CC introduced “Live Corners" in January of this year, I was overjoyed. They’d taken one of the most time-consuming and tedious tasks in transit mapping – generating properly nested sets of rounded corners where route lines changed direction – and turned it into something intuitive, quick and 100-precent accurate every time.

However, it didn’t solve every problem. Joining two separate paths into one (so that Live Corners could be applied to the new corner point) was still a laborious task that involved using the Scissors tool and hoping that it snapped to the paths properly, or a lot of manual pulling and pushing of endpoints until the two points aligned precisely (and it had to be precise, or you’d end up with two points very close to each other, one of which would have to be deleted before Live Corners could be used).

Despite their name, Illustrator’s Pathfinder tools actually do a lousy job with unclosed paths: only one of them –  Outline – works at all, and even then it strips all stroke attributes from the path in the process. So they’re not the answer, either.

However, the October update to Illustrator CC 2014 (version 18.1, if you’re keeping track) introduced the new “Join Tool” that hides away underneath the Pencil tool, as seen in the first picture above: and it’s simply fantastic.

Simply select the two paths you want to join, and then just lazily swipe over the bits of the paths that you want to be eliminated, as shown by the arrow in the second picture. That’s it! Because you’ve selected what you want to tool to affect, it doesn’t do anything to other paths nearby, like the cyan paths in the example shown.

As you can see in the third picture, Illustrator has instantly joined the two paths with a single point, that (in all my experiments at least) is exactly where it should be. It does also add some bezier anchors even though the paths are completely straight, which doesn’t seem to affect the subsequent application of Live Corners (picture 4). If it really bothers you or you like super-clean artwork (like me!), then you can click on the point with the Anchor Point Tool (Shift-C) to get rid of them before any further editing.

Submission - Washington DC Metro Cross Stitch

Submitted by ghostof-electricity, who says:

DC metro map cross stitch I made this summer. I moved away two weeks before the silver line opened so I chose to create the metro map pre-silver line, the way I remember it  :)


Transit Maps says:

Rectilinear transit diagrams lend themselves well to cross stitch, but this is one of the neater ones I’ve seen. Nice work!

  1. Camera: iPhone 4S
  2. Aperture: f/2.4
  3. Exposure: 1/20th
  4. Focal Length: 4mm

Historical Map: Railway Clearing House Junction Diagram of Buckinghamshire, 1911

Not a true map, but what the Railway Clearing House (RCH) called a “Railway Junction Diagram”. Note that while railway lines, stations and junctions are faithfully and accurately depicted, not a single other detail is shown. That’s because these diagrams were created to assist the RCH in its primary task — the equitable apportionment of fares and receipts when trains from one railway company used the track of another.

Obviously, if a train from one company used its own track for an entire journey, the company was entitled to the full fare or fee. However, if that train had to use the track of other companies on its trip, then those companies would be entitled to a portion of the fare, usually based on pro-rated mileage. Before nationalisation of rail in Great Britain, there were many, many competing railways — both large and small — all entangled in a complex web of wholly owned and shared track.

The RCH was formed (and later enshrined by an Act of Parliament) to act as a broker between the railway companies to fairly settle any matters of trackage payment. Hence these highly accurate maps, with distances between stations and junctions marked prominently upon them to make computation of mileage easier. The measurements, by the way, are in miles and chains (a chain being 22 yards or 66 feet long: also the distance between the two sets of stumps on a cricket pitch). As befits the convoluted Imperial measurement system, the chain is also made up of 100 links or four rods, and there are 10 chains to a furlong, and 80 chains to a mile.


Railway Clearing House map of Buckinghamshire, 1911. The green spur is the Brill Tramway, which became the end of the Metropolitan Line of the London Underground until its closure in 1932. The multicoloured line up to Verney Junction at the top was the other end of the Metropolitan; the red east-west line that it meets there was the Oxford to Cambridge route, known as the Varsity Line, which was shut in 1968. There are currently plans to reopen at least the western part of it, from Oxford to Bedford.

Work in Progress: McKinney Avenue Trolley Map - Current Service

This is pretty much the finished product, I think, barring any major errors. The MATA website states that there are 38 trolley stops along the route, but I can only find 37, even after multiple “drives” along the entire route in Google Street View. 

I changed the background colour from silver to beige after doing some prints: the whole thing just looked too drab and grey once on paper. This works much better and make the whole map seem a little visually lighter.

Points of interest are taken directly from the current official MATA map, although far more accurately located. The only addition is the the historic trolley barn, which I’ve also highlighted by using the M-Line’s distinctive maroon colour. The map also usefully includes MATA’s contact information and general hours of operation. The whole map is formatted to print out perfectly on a US Letter sheet with half-inch margins all around – handy for tourists to print out and bring along for the ride!

The route line itself shows direction of travel, as well as where the route is double-tracked (down McKinney Avenue itself). I’ve made an effort to show where on the road the tracks actually are – left-running, right-running or center-running – while the little “half-circle” stop symbols indicate which side of the road riders should stand on to board the trolley. Full circle markers are reserved for those stops where the trolley physically changes direction: the turntable at Uptown, and the current southern terminus at St. Paul & Ross.

Stops are generally named after the street they are on, with the nearest cross street as the second part of the name. This only leads to one less than optimal result, when the Cole & Lemmon stop is immediately followed by Lemmon & Cole. A few exceptions to the rule are also made for stops near notable landmarks – the Dallas Museum of Art, for example.

DART light rail stations are shown, but lower in the information hierarchy than the streetcar, or even the Katy Trail (in orange), a popular and important multi-use (bike/pedestrian) path that links Uptown and Downtown. The DART line up to Cityplace/Uptown station actually runs in a tunnel underneath the freeway, but I’m not entirely sure if that’s really an important thing to show on a map like this.

I’ve also made two other versions of this map: one for when the spur along Olive Street opens (reportedly very soon), and one for the final configuration with the full loop through the Arts District. All up, I’ve probably only spent 20 hours or so on this project, and that includes drawing the base map from scratch. Once I’m finally done, I’ll be reaching out to MATA to see if they’d like to use this map in any way.

Thoughts? Errors? Can anyone tell me where the mysterious missing 38th stop is?

Interactive Map: Evolution of the Beijing Subway, 1971-2015 (and Beyond!)

A simple little timeline map from CNN charting the rapid growth of one of the world’s largest and busiest subway systems. The exponential expansion that has occurred since 2006 (pictured above) is both phenomenal and just a little frightening. Despite this, the network is struggling to keep up with the transportation needs of the region, and the newest expansion plans call for more than 1,000km of track by 2020 — more than double the current length of 465km.  

Work in Progress: McKinney Avenue Trolley Map, Dallas, Texas

Thanks to Michael Champlin for inspiring this little project. I’ve been thinking of doing a more geographically-based map for a while now to break out of the routine of always doing diagrammatic transit maps, so when he sent me a link to the actual map (PDF, 5.6MB) that this heritage streetcar system in Dallas, Texas uses, I knew that something better could be done.

So here’s a work-in-progress screenshot. Most of the hard work has been done, but I’m still toying with a few elements here and there and adding the final informational layers on top. I drew the street map by hand in Illustrator, which is time consuming but rewarding. I did actually try to export the streets, parks and rivers from ArcGIS to style up in Illustrator, but got incredibly frustrated with the poor quality of linework from the City of Dallas’ GIS files: wonky curves, non-joined road segments, etc. It’d take me longer to clean that up than just draw it myself, so that’s what I did. At least I know what I’m ending up with when I do it myself!

The main experiment here – that I think is working well – is the bounding box around the two separate northbound and southbound stops along McKinney Avenue that share the same cross street (and therefore the name of the stop). This means I only have to label the stops once!

Other notes: the background grid is in quarter-mile increments, and the typeface is Good Headline Pro, which has a nice old world “Gothic” feel, but with a bit of a modern twist. Also: huge x-height and tiny descenders, which are great for this type of labelling work. The orange line is the Katy Trail, a popular multi-use path that’s an important part of the urban fabric of this part of Dallas.

Thoughts and suggestions?

Delightful three-dimensional representation of daily passenger numbers on Frankfurt’s streetcar lines in the early 20th century. Each strip of wood represents 4,000 passengers: the higher the wood, the more passengers on that section of line!

The figure is from Willard C. Brinton’s Graphic Methods for Presenting Facts, first published in 1914 and widely regarded as the first book on data visualization best practices. You can read the book on archive.org



It’s not easy to show passenger numbers on a transit network. But in 1914 all you need to do is use wood, as above, or strips of metal!

Photo: Giant Tube Map Wall at Transport for London’s Offices

I have to admit that I’m pretty jealous of this floor-to-ceiling Tube Map in TfL’s spiffy digs. It’s also magnetic and dry-erase marker proof.

Source: david_cunningham/Flickr