Why do we allow head-on collisions (and left turns)?

“Be safe honey, don’t make too many left turns!”

-wife of the future

A few years back, I started Speed Limit Zero to cast a critical eye on America’s pursuit of safety at all costs. Olives on pizza have to go, as do bones in chicken. We’ve banned buckyballs and outlawed Kinder Surprises.


I was amused when New York Mayor Bill deBlasio adopted Vision Zero for his new traffic safety campaign. He has since lowered New York City’s speed limit one sixth of the way to 0 mph.


Speed is a great thing, at least outside city limits. It keeps us awake, it makes us feel alive, and it lets us spend more time with our friends and family. It even reduces the likelihood of distracted driving. If you’re cruising down the highway at a hundred ten miles an hour, the last thing you’ll do is send a text. Driving gets safer when the act of driving itself is distracting.

The most dangerous part of driving isn’t speed but oncoming traffic—which doubles impact speeds—and intersections (which can see minor driver errors flare up into fatal collisions). It’s odd that divided highway speed limits aren’t far higher than they are, since society has decided to put up with relatively high speed limits on two-way roads. Similarly strange is the decision to allow undivided two-way streets, left-turns across oncoming traffic, and path-crossing (i.e. non-roundabout) intersections at all.


Instructions for a left turn:

  • Stop in the middle of the road.
  • Wait for a gap in oncoming traffic.
  • Time your crossing of oncoming traffic perfectly

    Note: do not turn your wheels to the left when you’re waiting. If you get rear ended your car will lurch forward into oncoming traffic.

The whole process is time consuming and high risk (that’s why UPS has sought to eliminate left turns from their routes). It’s a wonder that safety-obsessed America has not yet started attacking left turns en masse. The most common safety strategy is to buy the biggest safest car you can afford (read Malcolm Gladwell’s thoughts here—winter tires, cars with good dynamic safety, and further driver training are all but ignored).

Only Michigan has put forth a real effort to minimize the number of left turns, with the “Michigan Left.” It is a bloated, fragmented roundabout that involves plenty of crossings and demands vast amounts of real estate. Worse, it doesn’t fail gracefully, either in terms of driver error or electrical failure.


The Michigan Left at Big Beaver and Crooks:


There’s also the ever-present problem of oncoming traffic. Our willingness to have left turns available nearly everywhere we drive puts us in the sights of oncoming traffic and, when we slow to turn left, of cars approaching us from behind.

We are used to oncoming traffic, but it presents the biggest threat to us on our roads. People don’t flinch at a two-way road with a speed limit of 55, but 110 mph on the highway is a ticket straight to jail.


On mountain roads in France, traffic planners sometimes place a divider in the middle of the road to separate cars and motorcycles from oncoming traffic. It’s not practical to extend the divider all the way along the road because overtaking is sometimes necessary, but the dividers do make the corners safer.


In a city, where overtaking is never an option, what’s preventing widespread application of dividers? The obvious answer is the need for mid-block left turns.

If there were a roundabout at each intersection, however, drivers could easily get to a destination on the other side of the road, because roundabouts make U-turns trivial. Here’s how a city street thus arranged looks:


These physically separated opposing lanes on the main roads mean several things:

No head-on collisions.

No waiting to turn across traffic.

No waiting to pull out across traffic.

No dangerous left turns.

UPS would be proud.

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