Fogbreaker
There is a worn diagonal across the corner of a lawn near you. Someone laid a path at ninety degrees, everybody cut the corner instead, and the grass gave up.
The usual reaction is that this is a small failure of planning. It is more interesting than that, because the same mechanism that drew that line across the grass has drawn the lines you walk, and in your case nobody is going to come along and pave them.
Fifteen people is all it takes
The number is smaller than most people guess. As few as 15 passages over a site can be enough to create a distinct trail, and once a trail is visible it recruits: the next person walks it because it is there, not because they worked out the route.
That is the whole feedback loop, and it produces some large numbers. Detroit's Lower Eastside was measured at over 150 miles, roughly 240 km, of desire line as of 2010. When lockdown pushed people outdoors in 2020, Webster Woods near Boston gained 36% more desire paths, an amount the researchers put at 47 years' worth of normal creation.
The term itself comes from traffic engineering, not from landscape design. American transport planners used "desire line" in the 1946 Portland Metropolitan Area Traffic Survey to mean a straight line drawn on a map between an origin and a destination, and the 1959 Chicago Area Transportation Study used them to picture commuter choices. Landscape architects borrowed the phrase later for the footpath in the grass, which is the sense everybody knows now.
Some planners have made peace with it. Finnish designers are known for waiting until after the first snowfall, photographing where the tracks actually go, and routing the paths there. Broadway in New York is believed to follow a trail developed by the Wecquaesgeek, which makes it the oldest desire path most people have walked on.
Now the uncomfortable part
You are the grass.
Fifteen repetitions is also roughly what it takes for a route to stop being a decision. You walked to the station a few times, one way turned out fine, and you have not evaluated it since. Multiply that by the handful of places you go and you arrive at the state most people are in: four or five fixed lines, chosen years ago under conditions that no longer apply, running through a city you believe you know.
The difference between the lawn and you is the scale at which the shortcut happens. Across a lawn, the desire path is genuinely optimal, which is why planners give in and pave it. Across a city, the "shortest route to the station" is optimal for exactly one thing, getting to the station, and you were never asked whether that was the only thing you wanted.
What this looks like as area
Walking reveals a corridor roughly 30 metres wide, fifteen metres to each side.
Say you walk 5 km a day. Spread over streets you have not used before, that clears about 54 km² in a year.
Spread over five fixed routes of 2 km each, it clears 0.3 km². Not per year, in total, because a route walked 200 times reveals exactly as much ground as a route walked once, and the figure stops moving in the first week.
Same distance, same effort, same shoes. The entire difference is whether the line is new.
Four ways to use this
- Go and find the real ones. Desire paths are free route intelligence. Where one crosses a park, a verge or a fence gap, it is telling you the official network is wrong at that point, and it usually connects two things worth connecting.
- Walk the complement. Write down your five habitual routes. Then pick the streets that touch them but are not them. This is the cheapest possible intervention and the one nobody does.
- Use the fifteen rule on purpose. If a new route survives about fifteen walks, it stops costing you a decision and becomes the automatic one. That works in your favour exactly as often as against you.
- Look after snow or heavy rain. The Finnish trick works for your own behaviour too. Fresh snow shows you which lines you and your neighbours actually use, and they are never quite the ones on the map.
Making your own lines visible
The problem with the advice above is that your own desire paths are invisible to you. The lawn has the decency to go brown. Your route set leaves no mark at all, which is why people are genuinely surprised when they finally see it drawn.
A fog map draws it. The idea comes from strategy games: the map starts covered, and walking clears the fog in a strip around you, so after a few weeks you are looking at a photo negative of that lawn. The bright lines are your desire paths. The dark is everything you decided against once, years ago, without noticing you were deciding. Fog of war, but for real life explains how the mechanic works.
Fogbreaker turns it into a percentage per neighbourhood with Territories, which matters here because a desire path is efficient and a rut is not, and until you can see the shape of the thing the two feel identical from inside.
The honest limits
Desire paths are not automatically good. Across sensitive ground they are erosion with a nice name, and on restoration areas, dunes and alpine meadows the fifteen-passage threshold is the problem rather than the discovery. Where a sign asks you to keep off, the desire path is just a trespass that several people got away with before you.
And for the app: fog clears outdoors, on GPS. Fogbreaker is free on iOS and Android. If you would rather have a system for choosing new routes than a rule about old ones, finding new walking routes is the practical version, and if you live in a grid, every zigzag is the same length, which makes breaking a desire path cost you nothing at all.
