Part of the Bay Area News Group

and then the clouds parted

By enelson
Wednesday, May 2nd, 2007 at 6:47 pm in BART, Buses, Caltrans, driving, Freeway collapse, Freeways, Funding, Transit vs. driving.


There’s got to be some gloom and doom out there, I just know it.

But today Gov. Schwarzenegger announced that the closed ramp from westbound I-80 to southbound I-880 isn’t so badly damaged that it needs to be replaced. The fix will take seven to 10 days, and the lesser of the two traffic hassles will be erased.

This morning I got on KQED’s “Forum” program and predicted, as I did here, that this morning’s rain was going to drive commuters from Antioch and Livermore back into their cars so they wouldn’t have to put up with waiting out in the rain for buses or trains.

Instead, we have BART ridership continuing to surge and traffic no worse than it is on a normal day. Yesterday was an all-time record, beating a seven-year-old ridership high set when both the Yankees and the Mets were in town to battle our home teams on both sides of the Bay.

I do have to thank Randy Rentschler, spokesman and lobbyist for the Metropolitan Transportation Commission, who was also on “Forum” this morning. He noted that people should be mindful of the impact of the detours for the collapsed eastbound I-80-to-I-580 connector.

West Oakland residents have suffered for generations from diesel exhaust from truck and locomotive traffic in and out of the Port of Oakland, along with all that interstate traffic in the MacArthur Maze, I-880, I-580 and I-980. Putting the traffic on Grand Avenue and other city streets just makes it slower and more emission-intensive.

Gloom perhaps, but not quite doom.

edie-and-cat.jpgNext time I want to make a prediction, I should limit my audience to my dog, Edie.

I-80 traffic photo by D. Ross Cameron-Oakland Tribune

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7 Responses to “and then the clouds parted”

  1. Bruce De Benedictis Says:

    You know, I wonder what the emission impact actually is. The slower a vehicle travels, the less fuel it uses, so the fewer emissions are produced. The only way emissions will be increased is when the traffic is stopped, and if the fuel usage is reduced enough, that will diminish the effect of stoppages, which happen often enough in heavy traffic even when everything is normal!

  2. MikeyP Says:

    FWIW, afternoon rush hour traffic on Jackson street through Hayward (from 880/92 to Mission) has been unusually heavy all week. I have no idea if this is simply coincidence or if this is due to 580 avoidance.

  3. South Bay Resident Says:

    The peak fuel economy of most cars using normal driving techniques* is around 50-60 MPH. At higher speeds, the amount of energy needed to overcome wind resistance increases dramatically. At lower speeds the car’s engine isn’t running near its peak efficiency. As a side note, there’s nothing magic about 50-60 MPH it just happens to be the speed that most cars are designed for; some cars, such as hybrids, are more efficient at lower speeds. The real killer about diverting traffic to city streets is that the traffic has to stop and speed up again. This wastes lots of fuel compared to cruising at a constant speed.

    *Odd driving techniques, such as running the engine at around 3/4 throttle near the peak of its torque band to accelerate from 15-30 miles per hour then coasting back down to 15 with the engine turned off can get your very good fuel economy (like 3 x the EPA highway rating), but it’s not good for the car and annoying as heck to those around you.

  4. Bruce De Benedictis Says:

    The speed of a vehicle’s engine depends on the gearing, not the speed the vehicle is traveling at. I suspect that peak mileage under constant running conditions is probably about 5-15 MPH, but that may be high. Shell Oil, initial sponsors of the gasoline mileage contests, said in their advertisements years ago that if you are about to run out of gas, you should reduce speed. I would tend to believe them rather than someone who has a history of citing unlikely statistics

  5. Capricious Commuter Says:

    Bruce, please try to keep the criticism to the stats. I can think of very few instances where describing a person commenting in negative terms is appropriate here. As for the information proffered, you can attack all you want. That’s what the blog’s all about.

  6. South Bay Resident Says:


    You missed half of what I was saying. To run a gasoline engine at its optimum efficiency, you usually need to be pretty near peak output with the throttle pretty far open. A gasoline engine running with a nearly closed throttle is really inefficient. This offsets many of the gains you get from driving at a lower speed. At 15 miles per hour rolling resistance (which doesn’t vary much with speed) is more important than air drag for most cars. While there are vehicles that have optimum fuel economies at speeds that low you’re just wrong about typical cars.

    Here’s a link to a US Government site on fuel economy that contains a chart of fuel consumption vs. speed which is typical of gasoline-engined cars (the charts for diesels and hybrids look different).

  7. Bruce De Benedictis Says:

    The chart on the page South Bay Resident cited says pretty much what I said: There is not much difference in fuel mileage from 25 mph to 55 mph. Whether it amounts to anything is not really clear. Car manufacturers would do well to make the point where the big bend in the curve come sooner and sooner.

    Of course, the real question is not automobile mileage, but truck mileage. That is what people worry about in West Oakland. All the sources say that diesel trucks get about 4 mile per gallon, except for CARB diesels, which get about twice that, without regard to speed. You get those figures for transit buses as well as trucks, so speed is clearly not much of a factor. The upshot is that there will not be much difference in pollution.

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