The Unintentional Road Diet

In June of 2015, one of the greatest experiments in road diets took place on one of the most prominent commuter routes in the United States. Ironically, it was entirely unintentional. One-third of the motor vehicle lanes on Memorial Bridge between Arlington, VA, and Washington, D.C., were closed to allow for emergency repairs. The repairs would last for many months. 

The bridge handles a whopping 68,000 cars per day. The Federal Highway Administration recommends that only streets with less than 25,000 cars per day should get road diets. Given the huge disparity in these numbers, a traffic apocalypse should have happened by now. It should be impossible to enter the District of Columbia from Virginia, unless you’re prepared to swim. U.S. Senator Tim Kaine of Virginia warned of “unbearable congestion” due to the closures.

So where is the apocalypse? Why aren’t people abandoning their cars mid-span and walking across, as though an invisible snowstorm had struck? Simple: motorists had warning and changed their habits.

A Wednesday afternoon: no apocalypse in sight.

The truth is that any road can have a successful implementation of a road diet. In the latter part of the 20^th century, Groningen, The Netherlands, narrowed a road with 4 through-lanes, a center turn lane, and 2 parking lanes. This was no unimportant side street, as it lies between the center of town and the central train station. The current configuration is now split into sections with 2 through-lanes, a bus-only lane, and two protected bike lanes. The turn lane is gone, as is a fair amount of parking. The road’s importance to motorists dropped as they found either alternative routes or chose a different mode, such as buses or bikes. Since the initial narrowing, parts of the street have been further restricted to motorists, with buses getting priority.

How can the Dutch stand all this gridlock?

The obstacle to road diets isn’t the traffic count. It’s politics. Even when the traffic count is low, politicians will thunder forth about the need to keep motorist convenience has a higher priority than the safety of people who walk or bike, as the mayor of Gainesville, FL, did in 2014. The mayor successfully campaigned to remove bike lanes from a road with a mere 14,551 vehicles per day. No evidence of congestion caused by the bike lanes existed, but political posturing is seldom backed by facts.

That is the inherent problem with the debate over road diets: those who oppose them use unverifiable anecdotes (to be generous) and never manage to offer scientific data to back up their arguments. That can be forgiven from a public that is largely uninformed on matters of transportation, but it is inexcusable from professionals in the field.

Consider New Orleans: much like another Dutch city, Amsterdam, the city is largely below sea level. That means the topography is ideal for biking and walking. But, as I found on a recent trip, current street conditions are hardly up to the Dutch standard. Bike lanes are rare, even though streets are often very wide. That makes life a little tough for all vulnerable road users, but many leaders in post-Katrina New Orleans recognize the need to better. So, the Baronne Street road diet project was put forward.

Nice lane markings, eh? When waiting on the streetcar, don’t stick your rear too far out in the street.

The Baronne Street project would be no mere set of stripes on the road, but a protected bike lane buffered from moving vehicles by a parking lane. The bike lane would be created via a reduction in motor vehicle lanes on a one-way street from 2 to 1.

Image courtesy of Bike Easy

As with all things, it isn’t considered perfect, but people who bike love it. Yet they had opposition from a transportation professional. 

A New Orleans transportation engineer  wrote emails to his supervisor claiming that traffic would be gridlocked with the loss of a lane. Although he cited little more than anecdotal evidence and an internal Level of Service (LOS) study, his emails were enough to persuade a judge to grant a temporary order freezing the project. Thankfully, the judge later ruled that there were no legal grounds to stop the project.

This engineer thought a shared lane, or sharrow, would suffice. Those who bike in New Orleans thought otherwise, which is why so many of them turned out to the public hearings on the project. So, why couldn’t this engineer produce anything more than discredited LOS modeling? Simple: scientific evidence that road diets cause congestion does not exist. 

The sharrow just visible to the right is fine, but only because the street is empty.

That should not be surprising. Transportation experts who are on the cutting edge of the field have long known that induced demand results from road expansions; why should the opposite strategy not produce opposite results? Even the state of California’s Department of Transportation, Caltrans, admitted recently in public that bigger roads cause more traffic (though I’d heard it from them at an event over a year ago). 

But old habits are hard to break, so Caltrans plans a monumental road expansion via a tunnel project in the Los Angeles area. I cannot argue that switching from surface parking lots (LA’s current freeway system) to underground parking (this project’s certain outcome) is progress.

The utility of wide highways is clearly not as scientifically supported as parts of the profession or the large swathes of the public think it is. Perhaps a few more completed road diets, even if somewhat unintentional like DC’s Memorial Bridge, will finally put an end to debunked, old-school, transportation thinking.