An astute reader named Paul writes with this query: “I work on 34th Street in Manhattan and watch traffic “cops” direct traffic as I walk to my office. As far as I can tell, these officers have nothing but a negative impact; they confuse drivers and pedestrians alike and simply offer no value above what traffic lights do. I understand the idea of having a police presence, say, on a parade day, but why always? Do you have any thoughts on this?”

The first thing to note is that in the world of traffic, every case needs to be taken on its own; so without extensive study of the flows and geometries of that particular intersection, it would be hard to offer concrete analysis. And I’ve not seen hard-core studies analyzing human control versus signalized control (but if anyone has, please let me know).

The second thing is that I’m instinctively sympathetic with traffic cops; after all, the only thing more dangerous than driving in traffic is standing in the middle of it. I must have spent an hour watching the police in Hanoi do their work at a massively tricky crossing, as pictured above. And Paul, you may feel better about the NYPD’s traffic cops after reading this New York Times piece.

But the question raises a number of interesting issues…

Namely, do we even need traffic cops? The first, as an engineer in a major urban DOT told me, is that traffic police are generally used, except in the case of signal failures or special events, at intersections where “driver behavior” is an issue. In other words, people are not obeying the signals, not letting pedestrians cross safely, interfering with pedestrian rights of way, and generally acting like cretins. This is why, for example, one often sees cops near the Holland Tunnel entrance in New York City — left to their own devices, cars (particularly from a certain, ahem, neighboring state) tend to “block the box,” as well as make life miserable for pedestrians. None of this good for throughput, efficiency, or safety.

So the intersections where we tend to see human traffic cops tend to be the worst intersections to begin with (we don’t see them at the empty well-flowing intersections), and seeing them may reinforce the idea that they are somehow making things worse. In fact, things would probably be far worse in their absence. The traffic cop is a sign of our own failure; if we did as we were told, human supervision would not be needed.

In the early 20th century, as traffic signals were being introduced, to phase out human control (New York City got its first traffic cops in 1903), there was a raging debate over which system — man or machine — was more efficient. Burton Marsh, the first full-time urban traffic engineer in the U.S., argued in 1927 that “a competent traffic officer working at his best can usually handle traffic at an individual right-angle corner better than any other means of control of that individual corner yet developed…. the officer can take advantage of variations in the volume of traffic on the two streets and give to each street that proportion of time best suited to it at that minute.”

There’s one major drawback with having traffic cops control intersections, of course, as my DOT contact pointed out: They cannot effectively coordinate with other intersections “down the line.” So they may unwitting send too many vehicles toward a cluttered intersection two blocks away, and not enough toward an empty stretch of road in the other.

There’s one other potential problem, though I’ve not seen this in New York City. In many places — e.g., Moscow — traffic cops are famously corrupt. So rather than making things better they may just be “rent-seeking” as it were. Or, to paraphrase Chicago mayor Richard Daley, they are there “to preserve the existing disorder.” In Mexico City, they’ve tackled this problem in an interesting way: By hiring only women to direct traffic. The “swans,” as they are called, pictured below, are beacons of propriety and a delightful addition to the often mean streets of the D.F.

This entry was posted on Friday, June 13th, 2008 at 8:02 am and is filed under Etc., Uncategorized. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.