Articles by Clark Williams-Derry

Jammin’ on traffic

From Gordon Price's most recent Price Tags newsletter -- a computer simulation of traffic congestion that will run on any java-enabled web browser.

It's mesmerizing to watch "phantom" traffic jams form -- temporary slowdowns in traffic caused just by congestion, without any obstacle in the road.

And the especially nifty thing (or big time-waster) for me is that you can tweak the settings -- traffic volume, driver politeness, road setup -- to see what kinds of things lead to more congestion. For example, traffic that flows along smoothly when the speed limit is set at 80 km per hour (about 50 miles per hour) might completely jam up when the speed limit is bumped to 100 kph (or 60 miles per hour). And the same road can jam up when speed limits are decreased to 40 km per hour. This may seem either counterintuitive or completely obvious, depending on your perspective. In both cases, though, it's pretty easy to identify with the little dots stuck in traffic -- the congestion patterns are all too familiar.

As drivers, we tend to think that we exercise conscious control over what happens on the road-- which makes it easy to blame other drivers' "mistakes" when traffic slows down for no apparent reason, as in a "phantom" traffic jam. So it's instructive to see that little computer rectangles following simple rules show the exact same kinds of complex traffic patterns that humans create. Which is a reminder, perhaps, that the rules of the road can have more of an effect on real-world outcomes (traffic or otherwise) than our conscious choices -- which really is something to chew on while you're stuck in traffic.

Density Star

From the New Urban News comes this nugget:

Researchers presented findings at the Congress for the New Urbanism annual conference that show substantial energy savings from higher-density urbanism -- greater savings than can be achieved from the US government Energy Star program.

As the chart on the left shows (if you can read it -- sorry it's so small), even small increases in density can yield substantial energy savings; increasing residential density from 3 housing units per acre to 6 units per acre actually saves more energy than the average efficiency boost provided by Energy Star appliances.

Now, this shouldn't be much of a surprise, since it's been well established for decades that people who live in compact neighborhoods drive much less than people who live in more sparsely populated suburbs. Still, it's an important reminder: Neighborhood design is a powerful determinant of how much energy we use.

But for some reason, when people talk about making our transportation system more fuel efficient, they typically talk about improving the efficiency of vehicles, rather than of neighborhoods. Efficient vehicles have a high-tech cachet, I guess. But if anything, efficient neighborhoods are even more important than efficient vehicles. Hybrids and biodiesel vehicles do save fossil fuels and reduce pollution, obviously; but by reducing how much people need to drive, efficent neighborhoods not only save fuel, but also reduce other costly externalities, ranging from highway spending to car crashes.

The question of whether to buy locally grown food is not as clear as it might appear.

When shopping for food, how important is it to buy local? This question isn't rhetorical: I no longer know quite what to think about this. Obviously, transporting food long distances requires fossil fuels and creates air pollution, among other ills. So all else being equal, it's better to buy local. But how much better, I'm just not sure.

Studies such as this one (reported on here by the BBC, blogged about here) suggest that, in terms of net environmental impact, it's even more important to buy local than to buy organic. The authors of the study didn't look at human health issues, but did attempt to quantify all sorts of environmental "externalities" -- i.e., costs not borne by the consumer -- resulting from food production. And they found that transportating food was far and away the largest component of external environmental costs. In other words, the closer to home the food is grown, the better it is for the planet.

Critics of new urbanism’s grid street pattern miss the point.

One of the defining characteristics of sprawl is a branching street pattern -- one in which cul-de-sacs feed residential streets, which feed local arteries, which feed thoroughfares, which ultimately feed freeways. It's a design that can work fine for cars, but not so well for people. I spent (or misspent) part of my childhood in that sort of neighborhood. There were houses that were literally 100 yards from my house as the crow flies, but nearly a mile by the road network. That sort of thing discourages, you know, walking and stuff. Which is one reason why people who care about promoting walking and biking as transportation prefer an interconnected street network to a hierarchical one.

Now, Wendell Cox, a smart-growth skeptic and fellow of the Heartland Institute, writes in defense of the cul-de-sac: