To Widen or Not to Widen

Jim Rowen is wrong.

Fellow blogger Emily Mills posted her reaction to news that the Wisconsin Department of Transportation is planning on widening I39/90 from the Illinois border to Madison from 4 to 6 lanes. I was going to respond via a comment but it got rather lengthy so I've decided to note some things in a proper post.

With Americans driving less in the wake of inflated gas prices and government making overtures towards improved public transportation, Emily asks, "Why, then, spend hundreds of millions of dollars on an interstate expansion?"

The Cap Times article indicates why the expansion is being sought:

"Increased volumes of traffic on the interstate prompted the DOT to start looking at adding a third lane in each direction three years ago. The current average daily traffic count is between 47,000 and 68,000 vehicles a day."

The author or authors of the article ought to be taken to task for simply throwing out some numbers with no explanation. What do these numbers mean? Are travel times up significantly? Does this volume exceed a safety threshold of some kind? 99.9% of readers do not work for the DOT nor have the planning/engineering knowledge to make sense of that statistic. The Cap Times apparently never bothered to ask anyone with the knowledge to explain. They also neglected to tell us how current this "current" traffic count is. When was it made? Three years ago when the plan was first hatched or this year? Before or after gas went above $4/gallon? I think it's reasonable to assume that the section of interstate is near or at capacity for a 4-lane highway. Certainly during the summer it is maxed out with people from Illinois vacationing in our fair state. And I wouldn't be surprised if we see an increase on this stretch with more people who lost their jobs in Janesville commuting.

I also have an issue with Emily's reasoning. She took an aggregate statistic and applied it locally. You can't look at national trends and assume that it applies wherever you go. For example, just because George Bush won the 2004 election doesn't mean you can randomly pick a county and assume that the majority of people there voted for him. Similarly, while the nationwide trend is towards less driving, that doesn't mean that any given stretch of highway will see less traffic. You have to look at the traffic volume on a case-by-case basis.

One commenter noted the potential for Amtrak service to Madison. We really don't know how much congestion relief Amtrak service would provide, if any. For one thing, we have no idea how often the train would run. Currently it makes its Chicago<—>Seattle run once a day in each direction. While we may get Amtrak service here in Madison, I am doubtful that we will have the Empire Builder running through town more frequently than it does now. Plus the train would be coming in from Milwaukee – how likely are folks in Chicago's exurbs going to head east, nearly to the Lake, to catch a train that would bring them back west? I find any notion that Amtrak service in Madison would decrease traffic on the stretch of interstate at issue to be dubious.

Before anyone makes their mind up about this project, they should be considering the many variables at play and be asking a multitude of questions. Here are a few:

1) What is the daily average traffic count here in the second half of 2008?

2) What is the capacity of a four-lane backbone highway?

3) What are the projections for traffic volume over the coming decade and how were these numbers calculated?