Friday, July 10, 2009

Interesting tidbits from Texas Transportation Institute Study

Television and newspaper coverage of the new Urban Mobility Report from the Texas Transportation Institute (TTI) has emphasized the $300 million annual cost of traffic congestion to Milwaukee area commuters while also acknowledging that Metro Milwaukee's traffic conditions are tame when compared to other urban areas.

A review of the full set of performance measure data yields several additional interesting tidbits and questions that may be relevant to taxpayers and elected officials as we prepare for billions of dollars of expenditures on I-94 reconstruction and expansion and a major overhaul of the Zoo Interchange, and as we continue to debate new transit options for the region. Here are a few:

  1. The mobility data - which tracks back to 1982 - indicates that while freeway congestion levels in Metro Milwaukee grew considerably from the early 1980s to mid 90s, they have leveled off since then. For example, while the average Milwaukee peak hour commuter suffered seven hours of delay per year in 1982, that number tripled to 21 in 1993. Since that time, however, it has stayed about the same, and even decreased to 18 in both 2006 and 2007. Does this finding cast doubt on the accuracy of repeated projections that traffic congestion in Metro Milwaukee would grow precipitously without major investment in added freeway capacity? Or, conversely, does it support the value of investments we have made on a new Marquette Interchange and other improvements? Does the data speak mainly to freeway congestion, which may have reached its natural limit, as opposed to congestion on parallel arterials, which may have increased instead? Also, how does this finding mesh with recent projections utilized to plan the I-94 and Zoo Interchange projects?

  2. A key indicator used by the Texas Institute is a Travel Time Index, which measures "the ratio of travel time in the peak period to travel time in free flow". Milwaukee's Travel Time Index in 2007 was 1.13, which means a trip that would take 20 minutes in free flow conditions would take 22.6 minutes on average in peak periods. Again, a look at the historical trend shows that this index leveled off in the mid 90s and is lower in 2007 than it was earlier in the decade. But what is perhaps most striking is just how low the index is. With an average two-and-a-half minute delay in peak conditions versus free flow for a 20-minute commuter, should we be surprised that highway expansion proposals often are contentious? Likewise, is the lack of intolerable traffic congestion in Metro Milwaukee perhaps the biggest reason why proposals for modern transit investments have not taken hold here as they have in other cities? Should the other benefits associated with such transit investments really be the basis for our deliberations?

  3. TTI tracks "operations strategies" utilized to manage congestion from 2000 to 2007. This data indicates significantly greater usage of three such strategies in Milwaukee: freeway ramp metering, freeway cameras, and better signal coordination on arterials. Is there a need to further explore the causal relationship between these lower cost strategies and steady congestion levels in Metro Milwaukee before we consider costlier alternatives?
There's a lot of data in TTI's report, and it certainly can be used by advocates on all sides of the transportation spectrum to make the points they wish to make. Let's also hope that in the course of our upcoming transportation deliberations, those presenting options to policymakers and citizens also make fair and objective use of it.

1 comment:

Dave Reid said...

It also appears from the data that removal of the Park East Freeway had little or no impact on congestion In fact it looks like a slight decline occurred after its removal.