Are road diets the next big thing for US cities?

Does Chicago really need all those lanes? Image: Getty.

Like so many new concepts in urban planning, road diets seem like a great idea at first. And, like so many concepts in urban planning, they tend to generate a lot more criticism once they’re put into place.

The idea of a road diet is simple: to pinpoint streets that have excess capacity and could be narrowed down without significant car congestion, so providing space for other uses, such as sidewalks and bike paths.

It’s also an almost exclusively American concept, which makes sense; while streets in Britain and other European countries aren’t exactly crying out to be narrowed down, on the other side of the Atlantic, the streets seem to be the only thing wider than the country’s waistlines.

The roots of the concept date back to the 1970s, but it only began gaining traction over the past decade, loosely connected with other movements such as smart growth and complete streets.


Planners in the US began studying cases in which city streets had been widened to improve traffic flow for cars. They found that, in most cases, these projects did little to improve traffic flow, while creating an enormous increase in accidents. For instance, a study done in Fort Madison, Iowa, showed that while widening a main road led to a traffic volume increase of 4 per cent, it also increased the accident rate 14 per cent, and the injury rate by 88 per cent.

The obvious response to these findings is, naturally, to slim wider streets back down. But this slimming down can take many forms: widened sidewalks; replacing four-lane highways with three-lane ones, in which the middle lane is for those turning; and separated bike lanes. Last year, urban planner and author Jeff Speck teamed up with animation specialist Spencer Boomhower to create a series of videos showing the many possible forms road diets can take.

How effective has the concept been? In the US, road diets have seen a number of success stories. In New York City, a 2013 study revealed that road diets there had “significant safety benefits”.  They’ve seen success on the west coast, too: a pioneer in road diets, San Francisco has implemented 34 road diet projects over the last four decades, with favourable reactions from traffic engineers. Similar projects have also been implemented successfully in nearby Davis, California.

A street in Davis, CA, before its road diet. Image: Transport Observer/Wikimedia Commons.

But though road diets have allowed some cities to slim down their traffic safety problems, others have found that sticking to road diets is harder than sticking to actual diets.

Take Carolina Beach, North Carolina. Back in 2010, planners implemented a road diet on Lake Park Boulevard, one of the city’s main thoroughfares, in a bid to make the city more bike friendly.

But the measure was met by howls of protest. Local businesses complained of decreased sales, and the city’s car traffic during holidays led to increased traffic jams. In 2012, the road diet was reversed.  

Down the coast, in Gainesville, Florida, a road diet was adopted in mid-2013 for a wooded stretch of 8th Avenue. Four traffic lanes were reduced to two on a trial basis.

While the trial decreased injuries significantly, it met with staunch criticism from drivers, inconvenienced by a difficult merge area created by the road diet. The new configuration remained for over a year, but it was finally removed after being voted down by the city commission in December 2014, though plans are in the works for adding a shared pedestrian/cycle path on both sides of the road.

The same street after its road diet. Image: Transport Observer/Wikimedia Commons.

Then there’s Los Angeles, which despite some noble efforts to reverse its car-centric status by expanding its metro system, lives up to its reputation in its efforts to pursue road diets. Back in 2011, an attempt to implement a road diet on Wilbur Avenue, deep in the depths of the suburban San Fernando Valley, was quickly put to sleep after massive neighbourhood outcry.

Even in Silver Lake, an LA neighbourhood packed with bike-loving hipsters, the policy is in trouble. A road diet on Rowena Avenue in place since 2013 has been the source of continuous controversy, including angry driver rants caught on tape, though it remains in place for the time being.


Though the reasons road diets fail vary city by city, their common underlying cause boils down to political convenience. By their nature, road diets create an immediate inconvenience for drivers – who tend to be more affluent and politically connected; to compensate that, there’s only the long-term promise of creating greater safety, and a more bike and pedestrian friendly urban environment. For local politicians eager for quick victories, this all too often proves to be a toxic combination.

The lesson is clear. Road diets have paid off for some US cities. But for others, powerful political forces and a deeply rooted car culture have made sticking to road diets as difficult as swearing off junk food.

 
 
 
 

This fun map allows you to see what a nuclear detonation would do to any city on Earth

A 1971 nuclear test at Mururoa atoll. Image: Getty.

In 1984, the BBC broadcast Threads, a documentary-style drama in which a young Sheffield couple rush to get married because of an unplanned pregnancy, but never quite get round to it because half way through the film the Soviets drop a nuclear bomb on Sheffield. Jimmy, we assume, is killed in the blast (he just disappears, never to be seen again); Ruth survives, but dies of old age 10 years later, while still in her early 30s, leaving her daughter to find for herself in a post-apocalyptic wasteland.

It’s horrifying. It’s so horrifying I’ve never seen the whole thing, even though it’s an incredibly good film which is freely available online, because I once watched the 10 minutes from the middle of the film which show the bomb actually going off and it genuinely gave me nightmares for a month.

In my mind, I suppose, I’d always imagined that being nuked would be a reasonably clean way to go – a bright light, a rushing noise and then whatever happened next wasn’t your problem. Threads taught me that maybe I had a rose-tinted view of nuclear holocaust.

Anyway. In the event you’d like to check what a nuke would do to the real Sheffield, the helpful NukeMap website has the answer.

It shows that dropping a bomb of the same size as the one the US used on Hiroshima in 1945 – a relatively diddly 15kt – would probably kill around 76,500 people:

Those within the central yellow and red circles would be likely to die instantly, due to fireball or air pressure. In the green circle, the radiation would kill at least half the population over a period of hours, days or weeks. In the grey, the thing most likely to kill you would be the collapse of your house, thanks to the air blast, while those in the outer, orange circle would most likely to get away with third degree burns.

Other than that, it’d be quite a nice day.

“Little boy”, the bomb dropped on Hiroshima, was tiny, by the standards of the bombs out there in the world today, of course – but don’t worry, because NukeMap lets you try bigger bombs on for size, too.

The largest bomb in the US arsenal at present is the B-83 which, weighing in at 1.2Mt, is about 80 times the size of Little Boy. Detonate that, and the map has to zoom out, quite a lot.

That’s an estimated 303,000 dead, around a quarter of the population of South Yorkshire. Another 400,000 are injured.

The biggest bomb of all in this fictional arsenal is the USSRS’s 100Mt Tsar Bomba, which was designed but never tested. (The smaller 50MT variety was tested in 1951.) Here’s what that would do:

Around 1.5m dead; 4.7m injured. Bloody hell.

We don’t have to stick to Sheffield, of course. Here’s what the same bomb would do to London:

(Near universal fatalities in zones 1 & 2. Widespread death as far as St Albans and Sevenoaks. Third degree burns in Brighton and Milton Keynes. Over 5.9m dead; another 6m injured.)

Everyone in this orange circle is definitely dead.

Or New York:

(More than 8m dead; another 6.7m injured. Fatalities effectively universal in Lower Manhattan, Downtown Brooklyn, Williamsburg, and Hoboken.)

Or, since it’s the biggest city in the world, Tokyo:

(Nearly 14m dead. Another 14.5m injured. By way of comparison, the estimated death toll of the Hiroshima bombing was somewhere between 90,000 and 146,000.)

I’m going to stop there. But if you’re feeling morbid, you can drop a bomb of any size on any area of earth, just to see what happens.


And whatever you do though: do not watch Threads. Just trust me on this.

Jonn Elledge is the editor of CityMetric. He is on Twitter as @jonnelledge and also has a Facebook page now for some reason. 

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