Most evenings I walk from my office through downtown Chicago to catch a Metra train home. The walk is 1.1 miles, heading South and West from State and Hubbard to Union Station’s Madison Street entrance. The direction I’m heading cuts diagonally across downtown, which creates a lot of flexibility when it comes to route choice. Regardless of which streets are taken, there are at least eleven intersections to pass through and upwards of 20 navigation decisions to be made along the way.
There are essentially three factors that impact how fast the entire journey will be.
1. How fast I’m walking
2. Weather
3. How much time I must wait at intersections
The real opportunity here is in defining a routing methodology that minimizes time not walking. I’m in direct control of my walking speed, and the weather bows to no man.
Over time, I’ve developed the following guidelines for route taking to minimize time not walking per trip to an average of 18 seconds.
Never wait by choice*
Every intersection choice point has two valid directional options—South or West. In most cases, waiting is not necessary because if one direction is blocked, the other is open. *This guideline must sometimes be overruled in order to stay away from the perimeter of the route.
Hop to it!
If I can run a few paces to make the tail end of a “walk” sign, I’ll do it. The extra benefit is that when crossing near the end of light, I can immediately turn and cross again when I get to the other side.
Maximize choice points
Every intersection that is not on the perimeter of the route contains 1-2 choice points, each with two valid directional options. For example, let’s say I’m coming south on the east side of Dearborn and I arrive at Wacker Drive. My first choice point is to either continue South on Dearborn (crossing Wacker), or to turn right on Wacker, (crossing Dearborn). Once either of these moves are made, I cross the street and immediately encounter my next choice point, continue or turn.
In most cases, choice should be made entirely by the “Never Wait” guideline, but there is another principle at play that makes it advantageous to wait for short times (if necessary) in order to stay away from the perimeter. The perimeter of route is where waiting happens, because there are no longer any choice points and directional options that don’t increase the overall distance of the trip. If the light is red, I’ve gotta wait. The guideline I use is to avoid the outside perimeter and the next block in from it until I’ve reached the Lyric Opera at Washington and Wacker. I may wait 8 seconds or less at an early intersection to ensure that I avoid perimeter woes.
Avoid multiple Wacker drive intersections
All intersections are not created equally. Waiting, if necessary, takes longer on intersections where at least one of the streets are two-way. I try to head quickly to cross the River, then if I’m not lucky enough to cross Wacker right away, I’ll walk west until I get to an intersection where I can cross without any waiting.
In conclusion
If I am optimizing for speed, this is how I do it. I may make another post some time about optimizing the same walk for beauty, which I have thoughts about too. Enjoy walking!
