Ponder the happiness of our State Street corridor while reading about “The Causes of Traffic and Congestion.”


File under:

“Attempting to address congestion with solutions that make it easier to drive can make the problem worse by continuing to make the car the preferred way to get around.”

Alternatives, anyone?

The Causes of Traffic and Congestion, by Andrew Price (Strong Towns)

There are many misconceptions in my local conversation about what does or does not induce motor traffic. Some of these misconceptions are:

  • Single family homes do not increase traffic. If all we build are single-family homes, this will forever stay a quiet neighborhood.
  • Commercial development does not increase traffic, because it does not add more residents.
  • Congestion is bad, and we should treat avoiding it as a priority.

Let’s dive into it: traffic, what causes it, and what we can do about it.

The Role of the Street Network
The largest contributor to congestion is the hierarchical road network. This is where you have local streets feed into collectors that feed into arterials that feed into highways.

The Strong Towns article on Dealing with Congestion explains why this is bad. We are funneling all traffic through a small number of streets, giving us a lower vehicle capacity as well as fewer redundancies for when things go wrong (creating a fragile road network where one clog can grind traffic to a halt), and artificially spaces things out by reducing what you can reach in a given distance (sometimes stupidly so as in the case where two houses share a backyard despite their front doors being 7 miles apart).

A highly connected street network (this can mean a grid, but can also take non-geometric forms such as the street network of a medieval city) is better because there are a ton of redundancies (a street closure does not matter if you have countless alternative routes from A to B) and distances are shorter as you can take a more direct route from A to B. Because the load is distributed over the many redundancies, we are no longer funneling all of the traffic over a small handful of collectors or arterials, so you are going to encounter less traffic along your way, even if all else (population density, amount of travel) remains equal.

Designating a main thoroughfare, with higher speed and greater capacity, to funnel traffic through is bad, even if it is part of a street grid. This thoroughfare will attract all of the traffic until it is so congested that it no longer offers a speed advantage over alternative routes (such as parallel side streets), and all people will do is complain how congested it is. This holds true any time we deal with funneling a flow: getting all cars to take the same road, asking all spectators to leave through the same stadium door after a sports game, making all travelers at the airport to go through a single security line, pushing all commuters onto a single transit line, getting all permit approvals to flow through a single queue, and so on. It does not take many people for it to feel crowded when everyone is concentrated in one place.

Snipping through to the conclusion.

Is congestion really a problem?
At the end of the day, we should not worry too much about congestion or traffic. Congestion is part of the solution, not the problem. Congestion is feedback that we have built a place people want to be. The response to congestion should be to allow that Mexican restaurant to open up 3 blocks away rather than 2 miles away. To create bus lines and bike lanes that give people alternative ways to get around. The incorrect response to congestion is to build faster and wider streets, because that just reinforces car dependency and all of the negative consequences that come with it.

To summarize:

Development can add traffic. However, development that brings amenities and people closer together and reduces the need to travel so far can actually reduce traffic. With a mixture of uses, you can achieve a high population density with very little motor traffic.

A highly-connected street network (either a street grid or organic) with many redundancies better distributes the load of traffic and is more resilient to disruptions.

Designated thoroughfares and bypasses create an illusion of traffic because they funnel the traffic through a single point (and with this comes the fragility of a single point of failure that can bring down the system).

Attempting to address congestion with solutions that make it easier to drive can make the problem worse by continuing to make the car the preferred way to get around.

We should not worry too much about congestion, because it creates demand for other modes of transportation and for amenities to be closer.