Traffic Signal Synchronization, Ctd.


MinnPost file photo by John Noltner

I was recently quoted in an article on traffic signal synchronization – an ongoing project in Minneapolis right now. I have a contrary view to conventional wisdom on this topic as I have been quoted in the article and expressed in greater detail here.

Communities like traffic signal synchronization because it is smart technology that can reduce congestion and increase traffic flow without making any geometric changes to the roadway system. My argument is that these technologies work a little too well – they actually create induced demand  which in the longer term leads to more congestion and air pollution and poor land use decisions. I’ll stand by my quote in the article in that traffic signal synchronization is a solution that becomes a victim of its own success.

Traffic Signal Synchronization – Why not?

I was having a debate over John Hilkevitch’s article a while back in the Tribune about synchronized traffic signals with a friend of mine. My friend was surprised that this technology, most impressively shown in the movie, The Italian Job, was not widely deployed in many major cities such as Chicago. Alas, we still rely on, in some cases, 1950s technology to power our traffic signals. The essence of his thinking was why had it taken so long to roll out this technology given its substantial benefits.

My response, colored by my experience (cynicism?) in transportation, was to be skeptical. Traffic engineering has long been full of promises on solving road congestion, with many solutions worse than the problem. When roads have been widened or new roads built, induced demand has been the result. If we make all of our signals “smart” and easy for people to drive in the city, what happens then? We’ll see a mode shift away from alternative transportation options as people discover that synchronized traffic signals make driving easier, thus increasing demand for driving. As Todd Litman notes,

Field tests indicate that shifting from congested to uncongested traffic conditions significantly reduces pollution emissions, but traffic signal synchronization on congested roads provides little measurable benefit, and can increase emissions in some situations (Frey and Rouphail 2001).

Making driving easier brings all the negative externalities to the fore: increased auto emissions, gas consumption and pressure on land uses to accommodate cars. Thus, while traffic signal synchronization seems like a good idea, the unintended consequences are likely to make the existing traffic congestion status quo even worse.

Update: Dom Nozzi, making many of the same points, explains this in better detail here.

SimCity 5

I have been a huge fan of SimCity since I was a little kid. I’ve played the original SimCity, SimCity 2000, SimCity 3000 and SimCity 4. I’ve played it on the Super Nintendo game system and on my phone. And I’ve been waiting patiently for a new release. And that new release is coming next year! SimCity is a great game for urban planners like myself. But, for many of us in the profession, it still leaves a bit to be desired. Hence:

Regions should be more “regional.” In SimCity 4, the city was still treated as if it existed in a vacuum despite the regional map and transport connections. For example, you could still place power plants and other polluting land uses near the edge of your city to minimize the negative externalities and these externalities would not be present in the adjacent city. This has to change. Also, how about the ability to have multiple regions or a megalopolis?

Transportation needs to be realistic. SimCity had a built-in bias for roads when utilizing the transportation network. Subways were often under-utilized, even expressways! If this is the case, then buildings should be drawn to support these uses. That means more “suburban sprawl” because, after all, those cars have to go somewhere.  I’m not advocating this, of course. What I would like to see is a balanced transportation network of roads, transit and bike/pedestrian infrastructure that is accurately modeled. We need to know that the transit systems we build will be utilized, and that bike and pedestrian infrastructure can reduce auto demand in a similar fashion that transit can.

Finance is critical. Admittedly, this might make the game impossibly difficult, but I’d like to see more realistic infrastructure and development costs. Revenues and expenses should be more realistic as should economic impacts on the city. How does the economy effect a SimCity? I’d love to find out.

Scale. Why do some factories that employ 500 workers take up the same land area as a middle class house? Why does an airport or seaport seem so small? I’d love to see a better sense of scale. Airports are gigantic and can the size of a city itself. Seaports often have huge areas for container stacking, railroad terminals and truck storage. These should be shown at a realistic scale.

These are just a few things that this urban planner has been thinking about. I am excited to play the next version of the storied franchise next year.