Germany Considers Slowing its Autobahn to Curb Emissions

Though Germany’s famous Autobahn highway system is world-renowned for its lack of a general speed limit, many people who haven’t driven on it are unaware that more than half its total length is governed by state and local speed laws. Now, with the Green Party poised to take power in the country’s third-largest state—which happens to play home to both Porsche and Mercedes Benz—the Autobahn may soon be losing a little more of its edge.

In recent elections, the state of Baden-Württemberg fell from the control of Germany’s more conservative Christian Democratic Party to a coalition composed of Greens and Social Democrats. Both parties have long favored imposing a national speed limit to help curb carbon-emissions, and in all likelihood will take action soon to do just that in Baden-Württemberg.

The Greens support setting the cap at 120 kph (or 74.6 mph,) while the Social Democrats have proposed a 130 kph number. German carmakers are fiercely opposed to any further taming of Autobahn’s thrillingly fast—though surprisingly safe—roads, citing the highway system as an integral part of the industry’s international image. Opponents also point out that only a tiny fraction of driving in the country actually takes place on limit-free stretches. (Recent estimates place that number as low as 2 percent.)

The Case for Slowing Down

55 mph

Over the years, numerous studies have confirmed that cars have fuel economy “sweet spots” that usually fall somewhere between 30 mph and 60 mph on the speedometer. Different models have different optimal efficiency speeds, but for every 5 mph they travel above those speeds, drivers can expect to lose about 5 to 10 percent efficiency. (This drop-off occurs because the effect of drag becomes more pronounced the faster an object moves against the air.)

The idea of lowering speed limits to save fuel is isn’t a new one. In 1974, the United States adopted a nationwide 55 mph speed limit on federal highways, in an effort to curb gas consumption in response to the 1972 oil embargo. By 1995 though, that law had been completely rolled back, with states free to set limits of their choosing. Today, the trend in places like Kansas, Ohio, and Texas has actually been to increase top speeds, not lower them.

A 2008 study by the GAO found that going back to a 55 mph national speed limit would decrease oil consumption in the United States by between 175,000 and 275,000 barrels per day (or by about 1 to 2 percent. Over the course of a full year, those gains could add up to more than 145 million barrels, saving American drivers as much as $15 billion annually at current market prices.

Even with gas prices threatening to soon surpass 2008’s record highs, the political climate in the U.S. may not yet be ripe for such a proposal. That could change, but in the meantime a growing population of hypermilers around the country are choosing to do whatever they can to optimize their fuel efficiency—without the threat of a speeding ticket looming above their heads.

For most hybrids, the optimal speed range falls at about 40 to 45 mph, but regardless of the kind of car you have, even cutting your target speed from 70 mph to 60 mph can provide noticeable fuel savings for drivers who spend a lot of time on the highway. Set it to cruise control, keep your tires inflated, and follow a few other simple guidelines, and those savings should become even more noticeable.

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  • Henry Stowe

    This is the most idiotic idea proposed yet. I am sympathetic to the idea of saving energy, but posting lower speed limits did NOT improve the fleet fuel mileage in 1974-76. According to Energy Information Agency figures, fleet fuel mileage in 1973 was 11.9 mpg. In 1974 it was 12.0 mpg, which was still below the 1968-72 levels. Fleet gas mileage did not start going up until the new CAFE requirements took effect in 1976-1980.

    To save energy people need to ditch their cars for one day a week, combine trips, cancel their road trips, and junk their gas guzzlers (if they can afford to do so). This will have way more of an effect than posting slow speed limits on freeways.

  • Dom

    Oh good grief. They already tax the wazoo out of fuel in Europe… I don’t think the Autobahn is killing the planet considering Europe has a great selection of really fuel-efficient cars.

  • Dave S

    this is incorrect… Reducing the vehicles speed from let’s say 70 to 55 DOES improve fuel mileage. It doesn’t matter what you drive.

  • Pablo

    The velocity used in the aerodynamic equation is the relative velocity between an object and the flow. The aerodynamic force depends on the square of the velocity. Doubling the velocity quadruples the force. The dependence of lift and drag on the square of the velocity has been known for more than a hundred years. The Wright brothers used this information in the design of their first aircraft.
    The cross-section of the car “A” is also important.
    The density of the air is also important, so the speed limit in the mountain states could be higher.

    When optimizing the speed limit we need to put weight factors on the time spent for traveling and on the traffic accident statistics.

    I would say 75mph is good limit for Prius.
    The pick-up trucks and the SUVs have terrible shape and they need lover speed limit.

  • Evan

    The only thing did 55mph speed limit was allow police to ticket drivers more. No one slowed down.

  • Dom

    I’m not arguing the fact that slowing down improves fuel economy… I know that is true… though how much depends on the vehicle being driven. Seeing as most Europeans already drive fairly fuel efficient cars (especially their diesels which still get pretty decent fuel economy while cruising at high-speed), slowing down from 80 to 55 isn’t going to see the same savings as say slowing down a full-sized SUV from 80 to 55 here in the US. Besides, they’re talking about emissions not fuel economy, which though related are sometimes at odds with each other with regard to regulations.

    But all that said, sometimes it is worth it to the individual to get worse fuel economy to get to a destination quicker… time is money. Besides, as long as you’re not going under the minimum speed limit (if the Autobahn has one), one is perfectly free to drive slower, if one wishes to get better fuel economy or to save the planet.

  • tapra1

    while the Social Democrats have proposed a 130 kph number. German carmakers are fiercely opposed to any further taming of Autobahn’s thrillingly.Best UK Hosting