This week, excerpts from Todd Litman’s ‘Congestion Costing Critique’ – an analysis by the executive director of the Victoria Transport Policy Institute (and Planetizen blogger).
I’m going to take bite-sized pieces from his report in the hope that it will reach a wider audience than would normally dip into something so specialized and directed to professionals.
Why? Because Litman is taking on the Urban Mobility Report (UMR) – “a widely-cited study (by the Texas Transportation Institute) that quantifies and monetizes U.S. traffic congestion costs.” Every year when it comes out, media rush to report on the ‘most congested cities’ in North America – and convey without too much examination the conclusion that congestion costs us billions.
The implication, of course, is that government should spend billions to reduce it. And we do.
Hence the UMR is one of the most powerful tools of Motordom: the auto-dependent urban form that we have been building for most of the last century. Most recent local evidence: the Massey Tunnel.
So an understanding of the assumptions (and deficiencies) of the UMR is something even the general public should be aware of. Like this: “The UMR uses the terms commuter when the analysis only considers automobile commuters, ignoring other types of travelers.”
This week, we’ll look at other parts of the report in greater detail. First up, one of the most critical assumptions behind the UMR: speed is good.
The UMR uses freeflow speeds (level-of-service A, which reflects posted speed limits) as a baseline. For example, if a roadway’s legal speed limit is 60 miles per hour, and congestion reduces peak-period traffic speeds to 50 mph, the UMR considers the 10 mph speed reduction wasted time.
However, freeflow traffic speeds do not maximize system efficiency. Higher speeds require more shy distance between vehicles which reduces roadway capacity. For example, at 60 mph a highway lane can carry up to 700 vehicles per hour, about half of its 45-55 mph capacity (Table 2).
The lower speed range also tends to minimize fuel consumption and pollution emission rates (Barth and Boriboonsomin 2009). As a result, many experts recommend a much lower baseline speed, typically about LOS C, since that maximizes roadway capacity and fuel efficiency (TC 2006; Wallis and Lupton 2013).
As one leading economist explains: … all vehicles are deemed to travel at completely congestion-free speeds. This situation could never exist in reality, nor (in my view) is it reasonable to encourage public opinion to imagine that this is an achievable aim of transport policy.” (Goodwin 2003).
Because the Urban Mobility Report chooses a high baseline, the travel time costs are significantly higher than most experts and government agencies recommend A slower more realistic speed – i.e., the real world – would dramatically affect the presumed costs.