In 2013, 34 pedestrians died on the streets of Denmark. The city of Copenhagen, roundly hailed as the world's pleasantest city for walking and biking, has about 10 percent of Denmark's population of 5.6 million. We can extrapolate that exactly three pedestrians died in Copenhagen in 2013, for a rate of about 0.5 per 100,000.

To be sure, those three deaths deserve due lamentation, scrutiny, and sympathy. On the other hand, they deserve celebration. Copenhagen's pedestrian fatality rate is about as low as it gets. The lowest pedestrian fatality rate of any major American city is 0.76. Copenhagen's rate is a full five times lower than that of the City of Los Angeles, which, at 2.57 (pdf) is towards the high end.

If you divide Copenhagen's fatality rate by Los Angeles', you get 19 percent. The question that some in Los Angeles are now asking is, what happens when you divide by zero?

Founded in Sweden in 1997, Vision Zero is an international movement dedicated to reducing pedestrian fatalities to nil. Los Angeles Mayor Eric Garcetti supports Vision Zero enthusiastically. He made it is one of inspirations behind the new Los Angeles Mobility Plan 2035, which I reported on this month. In loose affiliation with a handful of other cities around the world and around the state -- including San Diego, San Jose, and San Francisco -- Los Angeles has pledged to calm traffic, improve sidewalks and crossings, enhance public transit, and do a host of great things that are, directly or indirectly, designed to make walking safer.

Safer is admirable and good, just as 2.57 is not good at all. Safer is especially good when it comes with collateral benefits and when multiple goals -- such as placemaking -- are achieved at once. But zero?

The trouble with Vision Zero is that, from the moment it was devised, it was destined to fail.

Even before I covered the Mobility Plan, Garcetti's embrace Vision Zero made me uncomfortable, for its both grandiosity and fantasy. How can Los Angeles -- or any other city in the civilized world -- ever hope to live up to such a stark, uncompromising goal?

Accidents are going to happen, even in Copenhagen. Someone is going to bust an inner tube and hit the curb. Someone is going to slip on a carelessly discarded smørrebrød and faceplant into an oncoming bus. Someone will get tangled in his scarf and end up in a canal. Even perfect cities aren't perfect.

The fact is, planning can never eliminate all bad things -- whatever the thing happens to be. In the case of pedestrian safety, it can absolutely reduce deaths. It can, if you go back to high school calculus, approach zero. But this is still a free country. Unless Los Angeles bans cars entirely and replaces all its pavement with compacted marshmallow, it can never reach zero. Not in 2015, not in 2035, not ever. In the battle between absolutes and public policy, policy never wins. 

As much as I admire the Swedes' approach to urbanism, Vision Zero strikes me -- in its rhetoric, it not necessarily in its strategy -- as a paternalistic extension of parents' paranoia over germs, dirt, boogeymen, and walking home from school. Should public policy look out for citizens' safety? Of course, but not maniacally so. And, more to the point, not inefficiently so.

Planning Commissioner Richard Katz notes that Los Angeles really shouldn't worry about traffic deaths. It should worry about all deaths.  There are four million ways to die in the naked city, from lung cancer to drug overdoses to gang shootings. Public policy should be prejudiced only by those cases that will yield the most lives saved. Then again, we can't repeal the Second Amendment, so we might as well fix our streets.

Laura Lake, who heads a group that is suing the city over the Mobility Plan, takes the Zero Paradox a step further. She notes that by slowing traffic on certain streets, the plan might impede ambulances that are responding to fires and medical emergencies. For every pedestrian saved, someone else might expire in a gurney on the way to the hospital.

Lake's hypothetical is, possibly, a bit out there. But these potential unintended consequences are surely worthy of discussion, especially when the Vision Zero movement is gaining so much momentum. That's a lot of preordained failure.

The planning field hasn't had much luck lately with vague, ominous slogans. (Agenda 21, anyone?) Let's hope that, unlike Agenda 21, Vision Zero faces not unhinged opposition but rather a more nuanced, thoughtful strategy than its name implies and a willingness to strive for realistic goals.