Remember the 55 mph speed limit? Remember… ignoring it? Wired’s Autopia blog is wondering if we should consider bringing it back. Back in 1974 Congress passed the National Maximum Speed Law, and threatened to cut funding to any state that didn’t comply with the new 55 mph maximum speed limit. Theoretically, forcing everyone to drive slower increases fuel economy, and the oil embargo had people stressed. But did the lower speed limit work? Did we save gas?
From Autopia:
The U.S. Department of Energy says gas mileage plummets above 60 mph and says every 5 mph above that speed is akin to paying an additional $0.20 per gallon for gas. But the American Heritage Foundation claims 12 years of 55 mph speed limits cut fuel consumption by just 1 percent. After Congress repealed the National Maximum Speed Law and 33 states raised their speed limits, the Cato Institute said traffic deaths dropped to a record low.
More than fuel economy and traffic deaths are at stake now. “Emissions increase pretty appreciably above 55,” McNaull says. drive55.org claims Washington state would cut CO2 emissions by 10 percent if it cut its 70 mph speed limit by 15 mph. But even here, the evidence is debated. The Automobile Association in England claims reducing the speed limit from 30 mph to 20 on residential roads would increase CO2 emission by more than 10%.
What do you think? Should we bring back the national speed limit?
With Gas Prices Rising And The Planet Warming, Is It Time To Drive 55 Again? [Wired]
Wow. 250 comments already? Not like anyone will read this, but here goes:
Isn’t fuel economy the same as carbon emissions? Since you can’t strip out carbon dioxide from the exhaust stream and assuming there is complete combustion at all speeds (or at least total carbon liberation), I think they’re the same?
the problem with bringing back the 55 limit is that there are decades of cars that are not geared for that on the roads. there are tons of cars that are not getting optimal fuel mileage at 55, but rather 65 or 70, and going slower would not save a dime.
Try maintaining 55 on a highway in your vehicle, you might be surprised at how it reacts.
Perfect example – my 2007 chevy trailblazer.
it tachs 1475 rpms at 55mph in top gear based on the math. But, at that rpm, the torque converter is not fully locked up, so unless you are fully off the gas, you will not see that rpm. What you will see however is slippage up to the 1800-2000 rpm range when you’re not really on the throttle, and if you’re above more than an estimated 1/8 pedal, the vehicle would downshift, and you’d be at 2100 rpms to stay at 55mph. So figure you would spend a third of your time at 1500, a third at 1900 and a third at 2100, that’s an average rpm of 1833, and a lot of shifting (as in transmission wear) to maintain it.
However at 70mph, the rpms are 1900 rpms all the time, since you’d be at lockup rpm, and even some light throttle would not cause a downshift. your rpms are a whopping 3% higher, which would have a negligible impact on gas mileage, you have better transmission life, and you get there around 20% faster.
@xAnarChisTx: “Well, by driving my gas guzzler, I am forced to have to drive 55.
And you know what? I SAVE MONEY!”
Why 55? Why not drive even slower.
I save money by driving faster so I’m really getting a kick outta these replies.
@Bladefist
If you don’t want goverment regulating your speed, then stop driving on the highways that THEY build…
I’ve been driving 65-70 instead of 70-75 for the last couple of years now. 55 is hard to do for me even on curvy two lanes.