Bad question, useless answers: Traffic policy GIGO | A Pragmatist's Take | Douglas Moran | Palo Alto Online |

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By Douglas Moran

Bad question, useless answers: Traffic policy GIGO

Uploaded: Sep 17, 2015

City Hall is currently requesting citizen input on fundamental policy related to traffic and transportation issues. The currently advertised question (via Nextdoor) is "Do you find that traffic calming is an effective way to slow traffic in your neighborhood?" The term "traffic calming" has been bastardized far beyond the point where calling it a euphemism would itself be a euphemism. What had been a useful approach has been usurped by ideology.

Start with the meaning of "calm": It does not mean "slow". Think about being in a crowded room, and someone announces that there is a fire nextdoor and asks everyone to "calmly" move to the exits. Would you interpret that as telling you to be "slow" in leaving the room? If so, you deserve to die in the fire (joke). Calming is about removing jitters, of smoothing out motion and thereby making it more efficient. A major goal and benefit of traffic calming is to make movements of the vehicles more predictable, and thereby increase safety.

One of the basic observations of traffic engineering is that people have an intuition about how long it should take to get between two points. If they are slowed down in one segment of that trip, they unconsciously try to make up the time in subsequent segments. That also means that reducing congestion in one segment can reduce the inclination, or incentive, to speed in others. In the Caltrans/El Camino Design Study of the early 2000s, emphasis was given both to raising the speed in the slowest segments and to lowering the speed in the fastest, with a goal of not changing the overall end-to-end travel time for the corridor.

From presentations by traffic engineers that I attended before the term was usurped, the most intuitive counter-intuitive example was that stop signs have a potential for creating more collisions and injuries than they prevent. The first effect is that people accelerate out of the stop sign, resulting in both less predictable movement and in speeds between the stop signs that are greater than without the stop signs. The second effect occurs for stop signs that are put at intersections with little traffic: People become so accustomed to there being no cross traffic that their (rolling) stops become perfunctory, and eventually there is cross traffic that doesn't mentally register, even though that vehicle is perfectly visible.

Another counter-intuitive example that I have learned not to attempt to explain is provided by metering lights on freeway on-ramps. Briefly, for the average trip, the time you wait at the on-ramp is more than offset by the higher speed on the freeway (because it is operating near its maximum efficiency).

Old-style traffic calming involves the art of engineering (cost-effectiveness, tradeoffs ...), with heavy doses of experimentation and evaluation. Different measures that produce traffic calming can conflict in many situations, and the circumstances of a particular location rarely match the "textbook" version.

However if you look at the Traffic Calming page at the Institute for Traffic Engineers (ITE), you will see little of this. For example, there is a the goal "to reduce the negative effects of motor vehicles on the environment(e.g., pollution, sprawl)" and an objective of "encouraging water infiltration into the ground".

How does traffic calming promote the stated goal of "promoting...transit use"? Answer: If designed "properly" (sarcasm), it will increase congestion to a level where it is more painful than using transit.

One of the well-known problems of slowing traffic in one place is that of diverting vehicles to other routes. So where do these rank in the ITE objectives? Slowing is first; "reducing cut-through motor vehicle traffic" is dead last, including being after "water infiltration" and landscaping. Are those your priorities? Do you think this ranking should be the City's?

One of the goals of the original concept of traffic calming was to reduce driver stress and distractions as an important component of improving safety for everyone (drivers, passengers, bicyclists, pedestrians). In the usurped version, safety isn't even a goal, and is present only as an objective and even that is reduced to being measured by frequency and severity of collisions. Which version do you think the City should embrace?

So here we have the City asking for public input using a usurped term where the key word is totally unrelated to what City Hall is going to "understand" it as meaning. And they haven't provided any examples of what is and isn't meant by the term. If only there were a system where you could, you know, click or touch a phrase and get linked to additional and clarifying information. Just thinking out loud.

The big question to ask of City Hall is what is their explanation for using a term that they know is utterly deceptive if it isn't to pursue a dogma/ideology that doesn't have public support?
And if they claim that they don't mean what is written, ask why they keep saying what they don't mean year after year.

As to "GIGO" in the title, that is an Information Technology acronym for "Garbage In, Garbage Out".
For those who expect homage to the Ancient Greeks: The playwright Euripides wrote "A bad beginning makes a bad ending" and, on the flip side, Aristotle wrote "Well begun is half done".

An abbreviated index by topic and chronologically is available.

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