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. CK says:

    In that case, we should continue to push for car-pooling, bicycling to work, and taking public transportation as well?

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  2. jimi says:

    Maybe Jews are just the worst drivers?

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  3. Eric M. Jones says:

    Alternatively, perhaps a lot of people become Jewish just for a day.

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  4. Jonathan Brown says:

    I’ve noticed the same thing in Boston traffic. In fact, my theory – rooted in conjecture which I will share with you now – is that if just 3% of the commuting population is off the road, traffic is fine – barring weather disruptions. Jewish holidays, Arab Holidays, school vacations, seem to work. I’m not a big fan of congestion tax – but maybe there could be a way of incenting more people to work from home….?

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  5. Dan says:

    Why not pay people to ride buses (or provide the ser vice for free).

    It could decrease vehicles on the road and stimulate the economy. (More people might shop if they can get there free (or get paid a small fee to ride)).

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  6. Traciatim says:

    CK beat me to it, I was going to mention that this should make the case that in order to improve traffic situations everywhere there should be huge pushes on to support public transit. Possibly even make the public transit system free or incredibly low cost.

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  7. MG says:

    Making public transit free can encourage riders, because everyone loves soemthing free. Additionally, this can improve bus efficiency. If the drivers doesn;t have to wait for people to deposit their exact change or show their pass, people can get on the bus quicker, and even use the backdoors to get on, so the bus can just get on it’s way faster. And if buses are quicker and punctual, that encourages ridership even more. Everyone wins.

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  8. Mike says:

    Some public schools now close on Yom Kippur. I think this has a more significant affect on things than getting all (or should I say many of) the Jewish drivers off the road.

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  9. 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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  10. 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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  11. 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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  12. 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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  13. frankenduf says:

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

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  14. 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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  15. 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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  16. 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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  17. Mike B says:

    The school holiday effect is far larger than the Jewish effect. I notice the same thing on election days in the city where I work because city public schools are closed on those days. Remove the buses, school staff and parents from the highways and thhe roads run very smoothly during the peak periods.

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  18. brett says:

    it’s definitely not ‘jews are the worst drivers’ – it’s OLD people are the worst drivers. get them off the road for the day, and everything gets better. see?

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  19. GEP says:

    Yes, yes, public transportation should be FREE. Just think of all the problems that would solve. Pollution, accidents, gas prices would drop. I remember visiting Ketchum, Idaho, years ago, and enjoyed their free buses. Hope they still have it.

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  20. Michael H. Wilson says:

    I’ve noticed a similar thing in Portland, OR. Every time there is a holiday where government employees are off the seats on the lightrail to downtown are virtually empty. As a friend once pointed out, you could roll a bowling ball down the center of one of the lightrail cars and not hit anyone.

    If the goal is to reduce the number of vehicles on the roads why not repeal some of the regulations that make it difficult for private owners/operators to enter the business?

    I could be wrong, but I understand that in most cities across the country it is difficult, if not impossible to compete in the urban transit market. Wouldn’t jitneys, ride sharing taxis and private bus companies help in a number of ways?

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  21. agb says:

    For three months, July, August, and September 1986, I commuted by car into northern Manhattan on the Palisades Parkway in northern New Jersey then across the GW Bridge. My trip took 1 1/2 hours in July and August, no delays, 2 hours after Labor Day, major delays both on the Parkway and at the bridge. Maybe a guess of 10% fewer drivers during the summer months. A small amount does make a huge difference in the carrying capacity of a road.

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  22. Heavy D says:

    IT was a new twist to the term, “Let My People Go!”

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  23. Al Dugan says:

    Not too hard to figure out. I commute by car 27 miles into Manhattan from NJ every day and have done so for the last 30 years. This current downturn in the economy has led to perfect traffic conditions. If I wasn’t so worried about my job, I would be happy that it takes me less than an hour to get in and 45 mins to get home.

    Easy to figure out how much the toll collections have dropped at the major crossings.

    I would much rather know the percentage of Jews who took off work on Yom Kippur vs the percentage of Jews who went to services. Any guesses?

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  24. Jonathan says:

    Same thing happened during the 1984 L.A. Olympics. Just enough people shifted their schedules because of a fear of traffic-to-end-all-traffic. As a result, traffic was the smoothest it has ever been.

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  25. Peter says:

    I noticed lighter-than-usual ridership on the Long Island Rail Road. Which meant a welcome break from the usual horror show.

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  26. susan says:

    Isnt the flow hyperbolic or inverted sort of parabolic curve?

    Isnt there that institute in Texas that notes the problem is the difference in comfort level related to distance from car in front? The idea is that is all autos are equipped with these infrared triggered controllers (like on some of the European cars – Mercedes, BMV, Volvo) that traffic would be smoother. (Cant account for the nuts who want to change lanes, though.)

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  27. aaron says:

    Don’t forget why the nonlinear build up is so strong. It’s the false believe that accelerating slowly is efficient. It’s the variation and slowness of acceleration rates that causes compounding congestion. And fast acceleration is also more fuel efficient.

    On top of that, as traffic builds, people are more likely to turn to distractions that delay people reactions to signal changes… and can be dangerous.

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  28. aaron says:

    Mike is also probably right that the reduction in school traffic has more of an impact than anything.

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  29. Ryan says:

    One of the best accounts of traffic I have read is by Philip Ball in his book- Critical Mass. If you haven’t read it check it out, it also has a nice overview of game theory (specifically the prisoner’s dilemma).

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  30. mike says:

    IBM in its efforts to be a nearlike God has a program called “smarter planet” In Singapore and some other european country they instituted higher tolls during rush hours to discourage people driving on congested roads. The other implementation was barring cars with the last character as a numerals on certain days from driving to push people to car pool or take mass transportation.

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  31. Toby Edison says:

    During the soccer world cup a few years ago Mexico was playing Brazil and the LA traffic was unbelievable light. I made it from Santa Monica to Anaheim (Disneyland) in 35 miles in 45 minutes including parking. If a small Jewish population can lighten the traffic load a little think about how a large latino population glued to the soccer match completely changes the traffic flow in the entire city.

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  32. Avi Rappoport says:

    Wow, I didn’t thing so many other people think that public transit should be free and frequent!

    In California, all the transit systems are cutting routes and hours, because the State is nearly broke. But subsidizing transit is a cheap way to cut carbon output, cut pollution, and cut traffic. Also, much less stress on bus drivers, no way to steal the money, and fewer resources spent on accounting.

    FREE AND FREQUENT, darn it!

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  33. dp says:

    This agrees with my anecdotal conclusion that rush-hour traffic in the Baltimore area on Jewish holidays is about the same as rush hour traffic during the summer. when some percentage of people are on vacation in any given week.

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  34. Peter B. says:

    Mike is right. Yom Kippur was an “unassigned day” for LAUSD, in other words there was no school.

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  35. doc says:

    Just imagine what the reverse is like on the first day of school when LA Unified’s 100,000 plus teachers hit the road at the same general time. Oy!

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