Utah clean air advocates asking lawmakers to hit brakes on increased speed limits

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SALT LAKE CITY - Drivers are hitting the roads faster thanks to increased speed limits and now some clear air advocates are slamming on the brakes.

The advocates say increasing freeway speeds is a step in the wrong direction.

Some are concerned the higher speeds could have a negative impact on air quality.

The group, Utah Mom's for Clean Airhas tried to roadblock increasing the speeds for the last year.

Group members said this could mean more fatal accidents and worsening air pollution.

However, studies by the Utah Division of Air Quality show there is little change in emissions whether you're traveling 55 mph or 75 mph.

Supporters of the speed increase argue people are already driving  70 mph anyway so the limit increase won't add to the air pollution.

Utah Moms For Clean Air founder Cherise Udell said, "It's basic math and basic law of physics that if you drive faster, you're going to get less miles per gallon, which means you're going to burn more gas and make more air pollution."

A member of Utah Moms for Clean Air has started an online petition urging UDOT to change the urban speed limit to 60 mph, lower than it was before the change.


  • Bobert

    People are already going 70+mph on most Utah Highways… Sounds like these mommies groups needs to get back in the kitchen and worry about some dirty dishes and making dinner…

    • Reuben

      Hi yes, if she can’t I can. Basically the speeds at which you get the most mileage for each gallon of gas you buy is between 40 and 60mph. I’ve experimented personally with those speeds, and you can also look up EPA MOVES studies for more information. Basically, if you’re going greater than 60 you’re efficiency goes down. Every gallon we use usually gets made by one of the three refineries here in Salt Lake City. So it’s safe to say that even though your emissions don’t rise tons between 60 and 70, they do some, and for all the gallons extra you spend to go faster, the refinery makes them, and pollutes a lot of nasty stuff to do so. I want to go faster too, I just don’t believe we can knowingly put more crap in the air than we’re already doing.

    • Cherise Udell

      Our (Utah Moms for Clean Air) technical advisor informs us that as a car goes faster, the form drag dominates the resistance to movement. The form drag is proportional to the square of velocity. Form drag (F) times velocity (V) is the power (P) you need to apply from the engine to the wheels to overcome that resistance. That’s the basic physics.

      So the math is F*V=P. And the power multiplied by the time you apply that power is the energy (E). Or P*T=E. The time (T) to go a given distance (L) is T=L/V. So E=P*L/V=F. Thus the energy to go a give distance, say a mile, is proportional to the form drag which increases with the square of velocity. Since the fuel burned to overcome form drag increases as the square of velocity, we pollute more and get lower mileage as we drive faster.

      Hope you find my answer to your question satisfying because I am back to the kitchen to finish the dishes.

      • Henry

        Your math and physics don’t take into account driving dynamics and differences in aerodynamics, engine efficiency and real empirical data. Let me help. Fleet fuel economy is defined as the number of miles driven by the number of gallons used for the overall vehicle fleet in the United States. During the 1970-1976 time period, fleet fuel economy fluctuated between 11.9 and 12.4 mpg, within normal statistical fluctuation for that and prior years. Fleet fuel economy did not break 13 mpg until 1980 when fuel economy regualtions were being more fully implemented and the vehicle mix on the highway began to change. The 55 mph speed limit affected no more than 30 percent of miles driven on the nation’s highways. A couple of things were responsible. The speed limit did not reduce driving speeds and the speed limit caused an increase in speed variance, enabling acceleration and deceleration as motorists attempted to pass the slower moving traffic. The result: the lower speed limit did not reduce gas usage.

  • BOB

    Utah Moms For Clean Air founder Cherise Udell has absolutely no common sense. The mayor of Seattle wanted to ban beach fires to improve clean air. That was while the entire state of California was suffering from a plague of wild fires.

    • jreu2e

      Hi Bob, I can’t agree with you there. I’ve watched her group for awhile and they work in smart ways to do something for all of us, namely, work towards making the air we all breathe, cleaner. Have a good one.

    • Tina Escobar-Taft

      That Cherise Udell with no common sense sure did just break down a complicated physics lesson for you, didn’t she? Do me a favor, the next time you want to question the SCIENCE of what we do, why don’t you warm your car up while sitting in your garage with the door down then tell us how stupid we are. OH! I have cookies burning, gotta go!

  • Robert

    Instead of limiting how fast we can drive, let’s limit households to two kids. More kids equal bigger cars now and more cars in the future.

  • Stephen

    This “environment” speed limit is motr political than environment or safety.

    Maybe 20 to 30 years ago before cats, but with modern cars the “emissions” are massively lower,

    The “group” calling on this calls are more on political limits, not environmental protection.

      • jcwconsult

        For JREU2E You cannot get cleaner air with lower posted speed limits, because posted limits have almost no effect on actual travel speeds, unless there is 24/7 enforcement everywhere – something no government can afford. All you get is increased speed variance with a few people who misguidedly obey the artificially low limits which increases passing, tailgating, lane shopping, uneven speeds, more diversion to lesser roads, and higher crash risks. The only beneficiaries of artificially low limits are the groups that get the speed trap revenue, including the insurance companies that surcharge the premiums of safe drivers who get tickets for the “dastardly crime” of driving safely with the main flow of traffic.
        James C. Walker, Life Member – National Motorists Association

  • Stephen

    “However, studies by the Utah Division of Air Quality show there is little change in emissions whether you’re traveling 55 mph or 75 mph.” Pretty much states the enviro nut group is full of it!

    • jreu2e

      Hi Stephen,

      The DAQ report highlighted three pollutants that stay at relatively the same level at the different speeds. The report does not talk about CO2, which is nasty, and does increase a lot as speed increases. Also, the faster you go, the more fuel you burn, and the more fuel you burn the harder the refineries work to supply you with more gas, and what they spew to give us that gasoline is far worse. Slowing down helps enormously. I’m working with DAQ to have them acknowledge just how limited their report to the legislature was. I’m calling on anyone in this valley that drives to voluntarily slow down and go a speed that gets you the furthest for the least amount of gas, namely, driving smoothly between 40 and 60. I know it seems a little nuts, but what’s even crazier is how little we’re doing about living and breathing in a super toxic cloud of pollutants all day every day. Believe me, I started the petition to ask people to go 60, and if it weren’t for our health, yours and mine, being affected by pollution I’d be the first guy around to be hauling down the freeway at higher speeds. Unfortunately that’s just not the world we live in. We’ve got to make some efforts to clean up our air.

  • James C. Walker

    The objections are nonsense for two reasons. 1) Posted speed limits have virtually no effect on actual travel speeds, setting limits to match the actual, current, safe travel speeds of most vehicles just makes them legal. 2) Modern vehicles emit almost no pollution at highway cruising speeds because the fuel is completely and efficiently burned. Most pollution is from cold start and acceleration at lower speeds in lower gears. There is one, and only one, real reason to post limits lower than the actual and safest 85th percentile speed of free flowing traffic under good conditions — that is to facilitate predatory and lucrative speed traps for tickets to safe drivers going along with the normal flow of traffic. This is an immoral but very profitable practice – one that should be illegal everywhere.
    James C. Walker, Life Member – National Motorists Association

    • jreu2e

      Hi James, Thanks for your comments. What you stated is only partially accurate. While it is true that a lot of emissions occur at start up and low speeds, plenty are still being emitted at higher speeds, and they do increase with speed. For example, at 60mph, a modern car averages an emissions of 330grams of CO2/mile, while that same car traveling at 70mph emits 400grams of CO2/mile. That’s been proven repeatedly and as much as I’d love to believe otherwise it’s indisputable. I encourage 60mph because it’s essentially the greatest speed most vehicles can travel while operating near their fuel efficiency peak. I agree that, HERE, the speed limits don’t have a lot of bearing on the rates people choose to travel. However, my experiences traveling on freeways in a lot of other Western cities, (Phoenix, Seattle, Portland, San Francisco, San Jose, Sacramento, to name a few…) the compliance to posted speed limits is far greater. I don’t know why. Fines in those states aren’t more than here. Maybe you could help me understand that. At any rate, for the reasons stated earlier I’m entirely for a lower speed limit, and I voluntarily travel slower. Our air is very polluted and traveling slower and more smoothly is one of many things anyone can do to reduce the problem.

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