Claim: cutting speed limits could slow climate change

Posted: August 14, 2020 by oldbrew in Emissions, Legal, Travel

The assertion being of course that human-caused emissions of the trace gas carbon dioxide somehow have a specific effect on the Earth’s climate, which must be countered. But if everyone is forced into electric cars, the speed limit argument becomes obsolete. Lower speed limits also mean more vehicles on the road at any one time, trying to complete their journeys, which in turn could lead to more traffic delays, potentially undermining the whole idea. As usual they conflate pollution and climate arguments to cause confusion.
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Canadian cities from Edmonton to Montreal are lowering speed limits, primarily in an attempt to save lives, says CBC News.

But slowing down may also be an easy way to reduce greenhouse gas emissions and air pollution — not just on urban roadways but also on highways (and even the high seas).

According to Natural Resources Canada, driving a vehicle with an internal combustion engine at 120 km/h burns 20 per cent more fuel than driving at 100 km/h.

An Ontario law that requires trucks to install technology to limit their speed to 105 km/h was estimated to have reduced greenhouse gas emissions by 4.6 megatonnes between 2009 and 2020.

That’s largely because air resistance increases exponentially at higher speeds, reducing a vehicle’s fuel efficiency and generating more pollution per kilometre.

In addition, certain pollutants such as nitrogen oxides are generated mainly at higher speeds, said Marianne Hatzopoulou, professor and Canada research chair in transportation and air quality at the University of Toronto.

That’s the reason the Netherlands recently cut its daytime highway speed limits from 130 km/h to 100 km/h. But Hatzopoulou said cutting speed limits can reduce emissions on city streets, too.

In both cases, it’s not just your maximum speed that counts but how often and how much you speed up and slow down, as a result of things like congestion and traffic control. “All these acceleration events will actually lead to higher emissions,” she said.

If a speed limit is set at 70 km/h, for example, cars try to accelerate to that speed at a green light, cruise very briefly at 70 km/h, then rapidly decelerate at the next red light. If the speed limit is 40 km/h, there’s a lot less acceleration and deceleration, Hatzopolou said.

Lower speed limits have indirect climate benefits, too. They can discourage car travel and, by making streets safer, encourage walking and cycling.

Full article here.

  1. oldbrew says:

    Lower speed limits have indirect climate benefits, too. They can discourage car travel and, by making streets safer, encourage walking and cycling.

    Are you more likely to walk if the speed limit is lower? The distance doesn’t change.

  2. Sartenada says:

    Yup. Less miles / kilometer and a gear free position in the downhill, also helps.

  3. A C Osborn says:

    I thought that everyone knew that the slower you go the more pollution is caused.
    Cars designed to run at 30mph in 4th gear need to run in 3rd gear at 20mph, so are less efficient.
    As well as that the vehicles are spending more time in the same area emitting exhaust fumes.
    Are these people really this dumb?
    No they just want us out of our cars altogether.

  4. Jim says:

    Yes they are. Amazing. Those people don’t car about the time of farm to market. Aerodynamics, or neat boxes they make you live in. You don’t see a Corvette shape on a pickup truck anymore. But you do see weak engines powering delivery vehicles that stall on load. Where the engineering could make a difference, it’s not used. Getting the product to a sales point, for use, Timley reduces wastage. Lowering the speed limit around the population centers, does not increase the viability of produce. It means produce must be picked while raw, and artificially ripened. Bad judgement. More chemicals in our foods.

  5. oldbrew says:

    Sartenada says: a gear free position in the downhill, also helps.

    A common assumption, but modern cars don’t work like that. Idling uses fuel, but if the car is left in gear with wheels moving but no acceleration, there’s zero fuel use because the engine management system cuts off the fuel supply.

  6. Chaeremon says:

    speed limit is an argument for fooling naive believers into thinking the wrong way.

    In my Swiss business we partnered with software model vendor, whose package we successfully sold and implemented in several regions, for switching traffic signs (in major cities, as well as for high-intensity autobahn junctions). All traffic obeys capacity restrictions which are result of architecture, service-level degree (i.e. maintenance), and actual demand. Everything else averages o_u_t 😉
    e.g. –

  7. Bob Greene says:

    The great thing about being an environmentalist is that you can recycle anything. Including failed ideas from the past. I guess it’s long enough that no one remembers just how well lowering the speed limits in the US to 55mph to save lives and fuels worked and just how much everyone enjoyed it. Give a bad idea long enough and some bright guy will reinvent it just like it was new.

    Terrible ideas are like the living dead. They just won’t really stay buried.

  8. A C Osborn says:

    I like that “Zombie Bad Ideas”.

  9. stpaulchuck says:

    During Carter’s 55 idiocy St Paul, MN to Elmhurst, IL (west of Chicago) took 7 hours+ at 60 mph (five over did not get the attention of the speed patrols). Instead we took a light plane from my aero club that cruised at 140 mph and it took about 2.5 hours with no fatigue. It was miserable on long trips at slow speeds.

    As for safety, at first the crashes went down but then as people got used to that speed the crashes started back up again. When the speeds went back to 60 to 70 mph some additional deaths occurred but then settled back down as the Darwin Award candidates eliminated themselves.

    With the newer cleaner engines I cannot see the current cars really “polluting” much at all except for the Satanic Gas – CO2. I’m hoping President Trump can get the pollutant designation for CO2 removed with presentation of real science to the courts that got pushed into that designation by liars and power seekers.

  10. oldbrew says:

    ‘Slowing down on urban roadways’ is largely pointless as they’re already choked up and slow, if not all day then in the usual rush hour periods at least.

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