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Transition to electric cars - lower speed limits?

  • 26-05-2021 7:31am
    #1
    Registered Users Posts: 45 ✭✭✭ Captain Lugger


    A thought provoking, or perhaps provocative, letter in The Guardian this morning about the ongoing ‘smart motorway’ controversy in England.

    The central argument is that lowering speed limits on conventional motorways saves more lives than ‘all lane running’ including the former hard shoulders. The writer also makes the interesting point that as the range of electric cars is 30% greater at 50 mph than at 70, fewer charge points would be needed. The other benefit would be that three lanes could be made into four, with a marginal narrowing of the hard shoulder.

    Given that transitioning from fossil fuel in Ireland by the end of this decade is going to be a big ask, to put it mildly, is this one way of freeing up scarcer power resources for homes and businesses? Ireland’s dependence on imported fossil fuels would seem to suggest so, but will the usual inertia prevent us from practical solutions until we face a crisis?


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Comments

  • Registered Users Posts: 489 ✭✭ grassylawn


    It's inefficient to drive faster than 105kmph in a ICE vehicle as well.
    The Energy Saving Trust says that the most efficient speed you can travel in a car in terms of achieving the best fuel economy is 55-65mph. Any faster, though, and the fuel efficiency decreases rapidly. For example, driving at 85mph uses 40% more fuel than at 70mph (oh, and it's illegal too).

    https://www.theguardian.com/environment/green-living-blog/2011/mar/25/hypermiling-tips#:~:text=The%20Energy%20Saving%20Trust%20says,%2C%20and%20it's%20illegal%20too)


  • Registered Users Posts: 3,305 ✭✭✭ Padre_Pio


    It may well feature if autopilot ever works.
    Slow everything down.
    Increase safety
    Increase range.

    Driver doesn't care since they're on Netflix.


  • Registered Users Posts: 489 ✭✭ grassylawn


    Padre_Pio wrote: »
    It may well feature if autopilot ever works.
    Slow everything down.
    Increase safety
    Increase range.

    Driver doesn't care since they're on Netflix.
    Though it's important not to confuse cruise control with autopilot.

    https://www.suffolkgazette.com/news/motorhome-crash/


  • Registered Users Posts: 3,305 ✭✭✭ Padre_Pio


    grassylawn wrote: »
    Though it's important not to confuse cruise control with autopilot.

    https://www.suffolkgazette.com/news/motorhome-crash/

    https://youtu.be/IfY49zx7RU0?t=56


  • Registered Users Posts: 1,229 ✭✭✭ Lurching


    People just love to change things, don't they?


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  • Registered Users Posts: 18,577 ✭✭✭✭ ELM327


    Absolutely nonsense.
    I've done over 150k km in Evs, most of that on the motorway at 120.


  • Moderators, Sports Moderators Posts: 43,442 Mod ✭✭✭✭ magicbastarder


    air resistance is exponential in relation to speed, and this matters not a whit if you are in an EV or an ICE car. so all vehicles become more inefficient above about 50MPH or thereabouts (depends on what the efficient sweet spot in their rev range is in top gear, i suspect)
    i think i remember that in the bugatti veyron, it took 150HP to reach 150MPH, and the other 850HP to reach 250MPH.


  • Registered Users Posts: 18,577 ✭✭✭✭ ELM327


    Drag squares with speed, so the faster you get the more energy you need to add the next 10km/h.


  • Registered Users Posts: 10,973 ✭✭✭✭ Calahonda52


    ELM327 wrote: »
    Absolutely nonsense.
    I've done over 150k km in Evs, most of that on the motorway at 120.


    Mens roomesque comparisons are not the issue here.
    Next we will have folk like unkel et al coming on telling us they did 500,000 kms all at blah blah , and never paid a cent in charging fees:D


  • Moderators, Education Moderators Posts: 26,348 Mod ✭✭✭✭ Peregrine


    From an ICE pollution point of view:

    The Netherlands reduced motorway speed limits from 130 km/h to 100 km/h at daytime to tackle NOx pollution.
    https://www.bbc.com/news/world-europe-50396037

    Similarly, the Welsh government introduced 50mph speed limits on motorways at a few built up areas to reduce NOx pollution.
    https://www.bbc.co.uk/news/uk-wales-48723302


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  • Moderators, Sports Moderators Posts: 43,442 Mod ✭✭✭✭ magicbastarder


    ELM327 wrote: »
    Absolutely nonsense.
    I've done over 150k km in Evs, most of that on the motorway at 120.
    as pointed out elsewhere, nothing of what you say here addresses the point being made in the article. it does not claim EVs cannot do 120km/h.
    the point is efficiency very noticeably reduces the faster you go (regardless of engine type)


  • Registered Users Posts: 1,746 ✭✭✭ Buddy Bubs


    As far as I remember the old mpg tests before wltp were conducted at 38 mph for the extra urban figure with all the panel gaps taped up. Always baffles me here when some people report getting the claimed fuel efficiency figures given by manufacturers. Are ye all driving around at constant 40mph the whole time or what?


  • Moderators, Sports Moderators Posts: 43,442 Mod ✭✭✭✭ magicbastarder


    huh, if you're to believe the onboard calculator on my car, i get not far off it (1.2Tsi petrol) - 5.3l/100km for the last few thousand km. that's 53MPG.


  • Moderators, Motoring & Transport Moderators, Technology & Internet Moderators Posts: 21,071 Mod ✭✭✭✭ bk


    as pointed out elsewhere, nothing of what you say here addresses the point being made in the article. it does not claim EVs cannot do 120km/h.
    the point is efficiency very noticeably reduces the faster you go (regardless of engine type)

    What Elm is getting at is that many people in the general public have this idea that EV's are slow (think milk carts) or have to stop constantly to charge.

    And titles like this thread and suggestions of having to reduce speed limits don't help with these misinformation, quiet the opposite, they reinforce it and will most likely slow down the adoption of EV's. It really isn't helpful at all.

    And of course it isn't true, most new EV's sold today can easily do Dublin to Cork/Limerick/Galway/Belfast at 120km/h without needing to stop to charge.

    And while I understand an EV at 120km/h will use more electricity then one at 80km/h. It would still be much cleaner then either a petrol or Diesel doing the same at 80km/h, never mind 120.

    If anything a better suggestion would be to limit petrol/diesel cars to the slow lane and 80km/h and allow EV's to do 120km/h in the overtaking lane. That would help drive faster adoption of EV's and have a faster and more positive impact on the environment.

    In the end, does it even matter that an EV is using some more electricity at 120, if most of it is coming from wind power anyway.

    What we need to focus on is getting the public to switch to EV's (and walking/cycling/public transport) as quickly as possible.


  • Registered Users Posts: 10,973 ✭✭✭✭ Calahonda52


    huh, if you're to believe the onboard calculator on my car, i get not far off it (1.2Tsi petrol) - 5.3l/100km for the last few thousand km. that's 53MPG.
    .
    53kW/100 kms costing 7 euro
    15kw/100 kms costing c 3 /1.5 euro day/night rate:)


  • Moderators, Motoring & Transport Moderators, Regional East Moderators Posts: 6,232 Mod ✭✭✭✭ liamog


    bk wrote: »
    If anything a better suggestion would be to limit petrol/diesel cars to the slow lane and 80km/h and allow EV's to do 120km/h in the overtaking lane. That would help drive faster adoption of EV's and have a faster and more positive impact on the environment.

    I believe Austria proposed this on motorways through urban areas. During periods of high emissions the speed limit is dropped down to 100km/h but EVs were allowed to do 130km/h as there are no local emissions.


  • Moderators, Sports Moderators Posts: 43,442 Mod ✭✭✭✭ magicbastarder


    bk wrote: »
    If anything a better suggestion would be to limit petrol/diesel cars to the slow lane and 80km/h and allow EV's to do 120km/h in the overtaking lane. That would help drive faster adoption of EV's and have a faster and more positive impact on the environment.
    i think if autonomous cars ever arrive, it'd offer a better opportunity to drop the max speed (regardless of engine type) - on the assumption that you could pack them more tightly onto the roads, and reduce delays due to stop/start traffic so that'd compensate for lower max speeds.

    that said, i don't particularly like the idea of even more cars on the roads.


  • Registered Users Posts: 45 ✭✭✭ Captain Lugger


    bk wrote: »
    What Elm is getting at is that many people in the general public have this idea that EV's are slow (think milk carts) or have to stop constantly to charge.

    And titles like this thread and suggestions of having to reduce speed limits don't help with these misinformation, quiet the opposite, they reinforce it and will most likely slow down the adoption of EV's. It really isn't helpful at all.

    I simply asked a question in the title of the thread and in the OP.I am very interested in EVs as we will have to transition to them eventually, but clearly asking questions about how we do that causes discomfort for some.


  • Moderators, Motoring & Transport Moderators, Technology & Internet Moderators Posts: 21,071 Mod ✭✭✭✭ bk


    I simply asked a question in the title of the thread and in the OP.I am very interested in EVs as we will have to transition to them eventually, but clearly asking questions about how we do that causes discomfort for some.

    What discomfort?!! Are we not having a discussion, the point of this forum?

    EV's don't require lower speed limits, they can operate at the current speed limit just fine (and much faster if you want).

    The title of this thread is rather provocative and all it does is help to damage the image of EV's and slow down their adoption.

    There is a discussion we could possibly have on reducing the speed limits on ALL cars on safety grounds, or we could discuss reducing the speed limit on petrol/diesel cars, while keeping EV's at 120km/h, which would immediately help reduce the environmental damage done by the majority of cars on the road which are petrol/diesel, while speeding up the adoption of EV's.

    But basically, no EV's don't need lower speed limits or anything of the sort. And it is pretty damaging to even make that suggestion.

    Instead we need to focus on how we speed up the adoption of EV's (+public transport) and how they can be a positive change to our lives.


  • Registered Users Posts: 45 ✭✭✭ Captain Lugger


    bk wrote: »
    What discomfort?!! Are we not having a discussion, the point of this forum?

    EV's don't require lower speed limits, they can operate at the current speed limit just fine (and much faster if you want).

    The title of this thread is rather provocative and all it does is help to damage the image of EV's and slow down their adoption.

    There is a discussion we could possibly have on reducing the speed limits on ALL cars on safety grounds, or we could discuss reducing the speed limit on petrol/diesel cars, while keeping EV's at 120km/h, which would immediately help reduce the environmental damage done by the majority of cars on the road which are petrol/diesel, while speeding up the adoption of EV's.

    But basically, no EV's don't need lower speed limits or anything of the sort. And it is pretty damaging to even make that suggestion.

    Instead we need to focus on how we speed up the adoption of EV's (+public transport) and how they can be a positive change to our lives.

    I am struggling with the concept that a thread title on boards.ie influences perceptions in Irish society about EVs, to the extent that their reputation can be damaged.


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  • Moderators, Motoring & Transport Moderators, Regional East Moderators Posts: 6,232 Mod ✭✭✭✭ liamog


    Given that transitioning from fossil fuel in Ireland by the end of this decade is going to be a big ask, to put it mildly, is this one way of freeing up scarcer power resources for homes and businesses? Ireland’s dependence on imported fossil fuels would seem to suggest so, but will the usual inertia prevent us from practical solutions until we face a crisis?

    There are a lot of assumptions built into this statement, could you give us an idea of how much power needs to be added to the grid to handle the nightly charging requirements of the private passenger vehicle fleet?


  • Registered Users Posts: 10,503 ✭✭✭✭ Cookiemunster


    liamog wrote: »
    There are a lot of assumptions built into this statement, could you give us an idea of how much power needs to be added to the grid to handle the nightly charging requirements of the private passenger vehicle fleet?
    It won't even be nightly charging. Most people will need to charge no more than once a week. With ranges in the 200-300km range, many won't even need to charge that often.


  • Moderators, Motoring & Transport Moderators, Technology & Internet Moderators Posts: 21,071 Mod ✭✭✭✭ bk


    I am struggling with the concept that a thread title on boards.ie influences perceptions in Irish society about EVs, to the extent that their reputation can be damaged.

    It isn't just your thread title, in your post you say:
    he writer also makes the interesting point that as the range of electric cars is 30% greater at 50 mph than at 70, fewer charge points would be needed.
    Given that transitioning from fossil fuel in Ireland by the end of this decade is going to be a big ask, to put it mildly, is this one way of freeing up scarcer power resources for homes and businesses? Ireland’s dependence on imported fossil fuels would seem to suggest so, but will the usual inertia prevent us from practical solutions until we face a crisis?

    You are making reducing speed limits about the transition to EV's which simply makes no logical sense for a number of reasons:

    1) EV's make up much less than 1% of all cars in Ireland. They have almost no impact on our energy usage yet, reducing the speed limit for them wouldn't move the needle at all.

    2) EV's use electricity which in 2020 was 44% renewables (mostly wind), growing to 70% by 2030 and 100% (carbon neutral) by 2050. So EV's aren't using some scarce resource, they will mostly use wind power, which isn't exactly in limited supply in Ireland!

    3) Most of Irelands electricity supply is not imported, like you make out. As of 2020, 44% wind and the rest mostly natural gas which mostly comes from our own sources (Corrib gas field).

    What is imported too Ireland is almost 100% of petrol and diesel for almost 2.8 million cars in Ireland. By comparison there is a mere 15,000 EV's in Ireland!

    Moving to EV's will actually greatly reduce our need to import foreign fossil fuels.

    Frankly it makes no sense to focus on EV's in this manner.

    A suggestion that might make sense is: "We should reduce the speed limit for ALL cars, as most are petrol/diesel, and that would give us an immediate reduction in carbon emissions".

    Or even better: "We should reduce the speed limit of petrol/diesel cars, while allowing EV's to continue at 120km/h, this would give us an immediate reduction carbon emissions, while promoting a speedier uptake of EV's".

    We need to find ways to speed up the adoption of EV's. Like London waving the congestion charge for EV's, Norway allowing EV's to use bus lanes (which I'm not in favour of), free road tolls, etc.


  • Registered Users Posts: 5,059 ✭✭✭ timmyntc


    i think if autonomous cars ever arrive, it'd offer a better opportunity to drop the max speed (regardless of engine type) - on the assumption that you could pack them more tightly onto the roads, and reduce delays due to stop/start traffic so that'd compensate for lower max speeds.

    that said, i don't particularly like the idea of even more cars on the roads.

    That only applies to areas where traffic congestion slows down the overall journey time. Most stretches of motorway don't suffer these issues, so you would ultimately be losing massive amount of time, and time is money.
    Shipping gets more expensive, travel times go up. Seems like a step backwards


  • Moderators, Motoring & Transport Moderators, Regional East Moderators Posts: 6,232 Mod ✭✭✭✭ liamog


    It won't even be nightly charging. Most people will need to charge no more than once a week. With ranges in the 200-300km range, many won't even need to charge that often.

    I was looking for a nightly average need for the fleet as a whole, the OP seems to think that it's a "big ask" I'd like the OP to give an idea of just how monumental the challenge would be, then perhaps we could discuss practical measures that could be implicated to mitigate the impact.


  • Moderators, Sports Moderators Posts: 43,442 Mod ✭✭✭✭ magicbastarder


    of course it applies to motorways? that was one of the cases i was thinking of, pertaining to rush hour.
    if you maintain a two second rule on a motorway, and an autonomous car can maintain a one second rule, it doubles the motorway capacity instantly?
    and in theory, fewer delays caused by inattentive drivers driving into other people too.

    yes, it may not apply to stretches which don't suffer from congestion, but i had hoped it was clear that wasn't the case i was talking about.


  • Registered Users Posts: 5,059 ✭✭✭ timmyntc


    of course it applies to motorways? that was one of the cases i was thinking of, pertaining to rush hour.
    if you maintain a two second rule on a motorway, and an autonomous car can maintain a one second rule, it doubles the motorway capacity instantly?
    and in theory, fewer delays caused by inattentive drivers driving into other people too.

    yes, it may not apply to stretches which don't suffer from congestion, but i had hoped it was clear that wasn't the case i was talking about.

    It applies to a few select sections of motorway - the majority of the motorway network doesnt suffer these issues. Not to mention dropping the speed limit would basically make motorway construction near worthless compared to the cheaper DC, given speed limits are similar.

    But what you're proposing would greatly increase journey times across most of the motorway network, only to "recoup" some of the lost time in the form of better traffic flow between autonomous vehicles - something that would happen regardless of speed limit.


  • Registered Users Posts: 7,694 ✭✭✭ Markcheese


    timmyntc wrote: »
    That only applies to areas where traffic congestion slows down the overall journey time. Most stretches of motorway don't suffer these issues, so you would ultimately be losing massive amount of time, and time is money.
    Shipping gets more expensive, travel times go up. Seems like a step backwards

    Shipping won't really
    be affected though - lorries and hgvs are already speed limited - and hgv fleet managers take fuel efficiency and fuel burn very very seriously ,
    For most commuters if it reduced stop start driving and hard braking and acceleration it could actually decrease journey times ,
    ( well in the short term , because increased road capacity would result in extra cars ,and increased congestion again )

    Slava ukraini 🇺🇦



  • Moderators, Motoring & Transport Moderators, Technology & Internet Moderators Posts: 21,071 Mod ✭✭✭✭ bk


    Yes, the OP is talking about issues that they are having with extreme motorway congestion in the UK, which mostly don't apply to Ireland.

    Most of our motorways are nowhere near congested, quite the opposite, except for the M50 and a small bits of approach to it.

    The M50 already has a lower 100km/h speed limit and there are plans for variable speed limits on it that go as low as 60km/h at peak times. The idea being similar to what magicbastarder is suggesting, that the lower speed allows for more cars to fit on the M50 at peak times.

    But this need certainly isn't there for the majority of the motorways between Cork/Limerick/Galway/Belfast and Dublin.

    I could see a possibility in the distant future when 100% of cars are self driving are all are linked together, where if traffic is light, they all agree to drive at 120, if traffic is heavy they all drive at 60km/h on that stretch to maximise usage of the road. It is a very compelling idea, but likely many decades out.

    I do think the idea of lower speed limits and variable speed limits are a better idea then just continuously widening existing motorways like Naas road widening, unless it is to build busways. We need more rail and other public transport heading into our cities.


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  • Moderators, Sports Moderators Posts: 43,442 Mod ✭✭✭✭ magicbastarder


    just a quick number crunch - based on a 2s rule, 100km means each car (leaving trucks etc. to one side) takes up 60m of roadway. 60km/h means 37m.
    but braking distances are not linear wrt speed, you'd essentially double the capacity of a road by dropping the speed. your individual journey may be slower, but the actual road capacity goes up.


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