Removing Travel Lanes in Boulder, Colorado

By Dom Nozzi

June 15, 2015

Removing travel lanes from a street is increasingly popular throughout the nation due to the fact that so many streets have been (very expensively) oversized due to conventional, tragic views in the past that widening a street would result in beneficial reductions in road diet before and aftertraffic congestion. What we have now quite conclusively learned is that widening a street will not durably reduce congestion, and the new car trips induced by the widening create a vast array of new problems.

Happily, most all cities which have removed travel lanes from oversized streets have enjoyed a great many benefits, such as improved safety, quality of life enhancements, better conditions for retail, and better financial conditions for local government, among many other large benefits.

The threshold “rule of thumb” I’ve always heard through the years to successfully remove travel lanes is 25,000 average daily car trips. Volumes above that tend to not be considered feasible for a lane removal, or at least very difficult.

There are a few things I would say to skeptics of lane removal in Boulder.

First, the traffic models used by the City of Boulder exaggerate problems with lane removal (that is, they make the impacts of lane removal seem worse than it will be in the real world) because the models used by the City don’t incorporate induced trips (caused by the original over-sizing of the road) or discouraged trips (discretionary trips that can occur at non-rush hr times, on different routes, on weekends, or be non-car, or not at all). Therefore, Boulder is using models that exaggerate problems, yet even such a flawed, exaggerating model clearly shows that lane removal is desirable and feasible on many Boulder streets. That tells me we can be rather confident there will not be meaningful problems.

Most congestion problems are created at intersections, not the street segments between intersections (in other words, it is the intersections that are the chokepoints, not the street width approaching them). Because Boulder often proposes to retain the double-left turn lanes at intersections, this is another reason why the lane removal should not be a problem. Note that there are a large number of reasons why I believe double-left turn lanes are highly detrimental, but because lane removal tends to be so beneficial, I’m willing to compromise and not fight against double-left turn lanes in order to make the lane removals more likely to succeed.

For the Iris avenue lane removal project proposed in Boulder, I counted EIGHT side street intersections without a left turn lane on the portion of Iris proposed for lane removal. When a four-lane street, such as that found on Iris, does not have a dedicated left turn lane at an intersection, left-turning cars at those intersections are doing so in a THROUGH lane. Each time a car makes a left at such intersections, therefore, Iris is ALREADY acting, functionally, as a three-lane road. Given the fact that there are eight such intersections on Iris, there would be a very, very modest loss of car-carrying capacity if two travel lanes were removed from Iris.

“Projected” traffic volumes these days need to be taken with a big grain of salt. Nationally, we are for the first time ever seeing vehicle miles traveled (VMT) level off and start to decline for a number of years. In Boulder, that trend is even more pronounced. Hard to imagine a growth in VMT in Boulder in the future.

A common argument is that it is impossible to remove travel lanes on a street when the community will grow in population size in the future. Where will all those new car trips go? One of my responses is to consider a large city such as NYC. If we look at NYC, say, 100 years ago, their population was small compared to the several million today. Are we to conclude that NYC should have been proportionally increasing the size of its roads to incorporate all the new car trips from the new residents?

In sum, lane removal for streets in Boulder is much more feasible than is thought by many.


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Filed under Road Diet, Transportation

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