A Gut Yontif for L.A. Drivers

As I was out driving on the recent Yom Kippur holiday (sorry Mom and Dad, but at least I fasted!), I enjoyed what seemed like a miracle: swiftly flowing traffic in the middle of the day on the streets of West L.A.

This was no fluke; there’s a big improvement in the Westside traffic situation every year on the Jewish high holidays. To many, this seems mysterious. True, West L.A. and the southern San Fernando Valley have large Jewish populations, but not that large. How can the removal of a relatively small number of cars be responsible for such a marked drop in congestion?

The reason is the non-linear way in which traffic congestion builds. Each car added to a road creates a very different amount of delay, depending on how congested that road already is when the car enters.

Quite obviously, many cars can be added to a facility without creating congestion at all as the road fills up.

However, when a road reaches capacity, order breaks down very quickly. At that point additional cars impose a comparatively large amount of delay, quite out of proportion to their small numbers. This slows vehicles upstream and ultimately throughout the entire road system.

The bad news? Since the addition of a relatively small amount of new traffic can cause lots of congestion, modest increases in, say, population or economic activity can result in considerable trouble.

But the good part is the converse: getting a fairly small number of cars off the road can greatly improve conditions. This augurs well for solutions like congestion pricing (which I blogged about here and here), because if dissuading only a few drivers will make a significant difference, the tolls may not have to be draconian.

Another option is hoping the Presbyterians do their part by discovering some new driving-light holidays of their own. But that’s pretty doubtful at this point. So why not think about congestion pricing? A small toll can have big effects.

Happy holidays!

(Hat tip: Martin Wachs, RAND Corporation)


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  1. Bruce Steinback says:

    But Eric, you’re supposed to be the transportation specialist! Certainly a fairly small amount of missing drivers does appear to make a big difference in traffic. Recessions here in Silicon Valley make a big dent in traffic, and probably only involve removing like 5% of trips. Has nobody done a study on figures? Agreed, it’d probably be a tricky test to setup, but using something like Jewish holidays might be an interesting start.

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  2. rusty says:

    As a regular public-transit commuter, I’ve gotta say, it’s going to take capital improvements to the infrastructure, more than just cash incentives, to get people out of their cars and onto the bus / subway. American public transit has never been a priority, and, as such, even when it’s “convenient” (relative to the rest of the country), people with cars see obvious benefits to not using it.

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  3. Rob says:

    Wouldn’t we just expect people to notice this phenomenon and start taking more trips on Jewish holidays to take incentive of the reduced traffic? It would still create a reduction in traffic, but not that much

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  4. rda says:

    These effects are only temporary, since a longer term improvement in traffic flow will bring more traffic when mroe people decide to drive, or more businesses and homes are built where the traffic is ok.

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  5. frankenduf says:

    the more obvious answer is that Jews drive more cautiously/slowly

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  6. Gary says:

    Rusty #10,

    I agree 100%t. Public transit in this country is mostly a joke. Here in DC where we have the Metrorail and Metrobus systems, I use a fair amount of public transport, but outside of peak hours, I seldom use the bus or trains. At 9 pm it takes me about an hour to get home from downtown DC via rail and bus. I can drive home in about 12 minutes. If they could get it down to 30 mins or so, I’d take the train everyday. Until then, I’ll stick with my car, at least for the nights I know I’ll be working late.

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  7. Brian says:

    I think public transport should be encouraged.

    I think there should be first class in public transport à la Paris in years past in their metro. Let’s see now…if I take my car, I get to sit down the whole way, but if I take public transport at rush hour (the problem times we’re talking about…) then I get to stand up and ride and get jostled by strangers.

    Why do airline flight attendants get apoplectic when you try to stand up when the plane is taxiing in, while on a city bus, it’s all you can do to hang on around corners. To say nothing of NYC’s screeching, lurching subways. Hey, if I could be assured a seat (maybe even with uphostery?) then I’d ride.

    Oh, and congestion tax? Phooey…that means trusting politicians. They’d soon take that money to spend elsewhere and raise the rates No thanks.

    Brian in Brooklyn

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  8. Vi says:

    A somewhat related tangential remark —

    I read in Tom Vanderbuilt’s book Traffic, that some parts of LA has the Jewish calendar programed into their traffic signal system. Since Jews cannot operate any machinery on holy days, they also cannot push the walk button for crossing intersections. Hence, there are certain sections of LA that automatically switch through the walk cycle on Jewish holy days even without anyone pushing the walk button.

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