22 September 2005


The picture above, of Houston residents fleeing Hurricane Rita provokes an immediate and obvious reaction. Has the world gone mad? Why aren't they letting people who are fleeing the city drive on the wrong side of the highway? Later in the day, they did just that. Too late, in my opinion, but credit where credit is due for finally waking up to reality. Allowing people to drive on the wrong side of the highway is called "contraflow" in traffic engineering circles.

The big question in my mind is not why it took so long to do it in Houston (see the section in my post on Conspiracy Theories about how people are frequently incompetent). The big question in my mind is why every major city in America doesn't routinely use contraflow approaches on a daily basis.

Traffic flows on interstate highways in major metropolitan areas are exceedingly predictable. Every weekday morning there is a rush going into the central city. Every weekday afternoon there is a rush going out of the central city. Indeed, this isn't the only place you see highly predictable traffic patterns on interstate highways. The road going to Vail is jammed every Friday evening and Saturday morning during ski season. The road leaving Vail is jammed every Sunday evening during ski season. This isn't rocket science.

I used to have a job in the suburbs at a time when I lived in my beloved central Denver Washington Park neighborhood. Every morning I zipped along Route 6 to the suburbs at 55 mph directing a smirk at the poor souls stuck in bumper to bumper 5 mph traffic going the other direction. On the occassional evenings when I got to go home as early as rush hour, I did the same thing in the evening. I know of no major city in the United States where this pattern does not hold true for at least some major highways.

Highways cost money. Lots of money. Adding a couple of lanes to I-25 between my downtown home and the Denver Tech Center, a project called T-Rex which will be finished at the end of 2006, cost $1.67 billion dollars to improve 17 miles of highway. For those of you who are math challenged, that means that adding lanes to interstate highways in the middle of urban areas costs about $100 million a mile.

Wasting billion dollar resources is bad. Very bad. It would be like Wal-Mart keeping three years of inventory in their warehouses at all times. They'd go broke. Yet, every major city in America does exactly this. They waste a couple of lanes of a six lane highway, every single workday, all through both rush hours.

It is not hard to build convertable central lanes in highways. Concrete dividers, road paint and traffic signs are far less expensive than building new lanes. While I'm going out on a limb here with a guess, I'd be willing to guess that they definitely cost less than $10 million a mile, and that's if you decide to hire Halliburton to do the work. Denver has a similar system with a couple of reversable central lanes on I-25 from downtown to Highway 36 to Boulder that are designated as HOV (high occupancy vehicle) lanes. But, the HOV component really doesn't matter. Chicago calls similar limited access lanes express lanes and lets anyone use them. The important thing is that if you can reverse central lanes you can add capacity at a fraction of the price of new lanes on the sides of the highway.

I'd be happy to see someone tell me that there is a good reason for not doing this routinely now. But, I sure don't see it. And, the picture at the top of this post could provide the extra boost necessary to get this idea implemented. A simple system for setting up contraflows helps when interstate highways are called upon to help evacuate cities, which was the official justification for creating them in the first place.

No comments: