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One could argue that self-driving cars potentially consume less energy by driving more efficiently than humans.

by sonnyp 10y ago

vkou 10y ago
We already have an energy-saving self-driving mechanism - cruise control (and obeying the speed limit.) I drive a hybrid. Except for a few parts of my commute, cruise control and slow acceleration push me from 42 mpg to 50 mpg on my commute.
- vonmoltke 10y ago
  > We already have an energy-saving self-driving mechanism - ... (and obeying the speed limit.) Obeying the speed limit is irrelevant; the actual speed is. A given car at a given speed consumes the same amount of fuel per unit distance regardless of what the speed limit is. All the data indicating that "speeding wastes fuel" is basically just proving that fuel economy is a function of engine power output.
  - Retric 10y ago
    You're ignoring breaking. If you go significantly faster than the speed limit your far more likely to break at highway speeds. Further, IC cars often get better fuel efficiency by mixing slow acceleration periods at optimum RPM and coasting. (Car engines get ~10-30 efficiency based on usage.) You can do this manually, but it's hard. However, air resistance is going to be the dominate factor at high speeds.
    - vonmoltke 10y ago
      > You're ignoring breaking. If you go significantly faster than the speed limit your far more likely to break at highway speeds. I'm not ignoring braking. Aggressive driving wastes a lot of fuel, but aggressive driving happens regardless of the posted speed limit. In fact, that rapid acceleration-brake cycle is more likely to happen when the flow of traffic is below the speed limit. > Further, IC cars often get better fuel efficiency by mixing slow acceleration periods at optimum RPM and coasting. (Car engines get ~10-30 efficiency based on usage.) You can do this manually, but it's hard. I don't think it's hard. It just requires paying attention to the traffic around you.
  - Houshalter 10y ago
    Actually it's more to do with air resistance. It increases exponentially at higher speeds. You also don't burn less by driving really slow, since the engine burns some amount of fuel just by running at any speed. 40 mph is the sweet spot, supposedly. Driving at the speed limit will definitely save you more fuel than speeding.
    - vonmoltke 10y ago
      > Actually it's more to do with air resistance. It increases exponentially at higher speeds. You also don't burn less by driving really slow, since the engine burns some amount of fuel just by running at any speed. 40 mph is the sweet spot, supposedly. Actually, the sweet spot is dependent on the design and condition of the car. I'm not sure where exactly it is, but I think you are right that it is usually around 40. > Driving at the speed limit will definitely save you more fuel than speeding. How does a number on a sign affect how much fuel I'm burning? If, as you indicated, the sweet spot for my car is 40 but the speed limit is 30, how am I saving fuel by going 30 instead of 40? What if the speed limit is 65? If they drop it to 60 am I suddenly using more fuel? If they increase it to 70 can I now go faster without using more? The speed limit is totally irrelevant to fuel consumption.
      - Houshalter 10y ago
        Of course it depends on the design of the car, but 40 is an average. >How does a number on a sign affect how much fuel I'm burning? I never claimed that it would. I said "Driving at the speed limit will definitely save you more fuel than speeding.", which is definitely true. If you speed you are going faster and using more fuel.
        vonmoltke 10y ago
        > I never claimed that it would. I said "Driving at the speed limit will definitely save you more fuel than speeding.", which is definitely true. If you speed you are going faster and using more fuel. That statement has nothing to do with the speed limit, though. It may be trivially true, but adding the speed limit ties an irrelevant variable to it. Speed limit is a semi-arbitrary number that has nothing to do with how much fuel a car uses and how efficiently it uses it.
  - sliverstorm 10y ago
    I think you're being deliberately obtuse. For 99% of people, obeying the speed limit will result in slowing down, which is what your parent was alluding to.
Houshalter 10y ago
Self driving cars will almost certainly use much more energy than regular cars. It will reduce the cost of shipping by a lot, increasing the amount of things which are shipped. It will reduce the price of taxis a lot, so people will drive more. And it will make long commutes and road trips much more convenient.
- toomuchtodo 10y ago
  Maybe, but you're still limited by atoms not occupying the same physical space at the same time ("traffic", "congestion", etc). There's limited road to use, so you'll still hit finite limits; if limits are reached, congestion charges will be used to bring demand inline with roadway supply.
  - Heliosmaster 10y ago
    ideally the throughput of highway would be increasing with self-driving vehicles: no need for start/stopping when they can drive at optimum total velocity.
  - agumonkey 10y ago
    Yes but the swinging hours pattern will melt since cars are now decoupled from humans cycle. Freeing a lot of pseudo-space.

One could argue that self-driving cars potentially consume less energy by driving more efficiently than humans.

by sonnyp 10y ago

One could argue that self-driving cars potentially consume less energy by driving more efficiently than humans.

vkou 10y ago

We already have an energy-saving self-driving mechanism - cruise control (and obeying the speed limit.) I drive a hybrid. Except for a few parts of my commute, cruise control and slow acceleration push me from 42 mpg to 50 mpg on my commute.

vonmoltke 10y ago
> We already have an energy-saving self-driving mechanism - ... (and obeying the speed limit.) Obeying the speed limit is irrelevant; the actual speed is. A given car at a given speed consumes the same amount of fuel per unit distance regardless of what the speed limit is. All the data indicating that "speeding wastes fuel" is basically just proving that fuel economy is a function of engine power output.
- Retric 10y ago
  You're ignoring breaking. If you go significantly faster than the speed limit your far more likely to break at highway speeds. Further, IC cars often get better fuel efficiency by mixing slow acceleration periods at optimum RPM and coasting. (Car engines get ~10-30 efficiency based on usage.) You can do this manually, but it's hard. However, air resistance is going to be the dominate factor at high speeds.
  - vonmoltke 10y ago
    > You're ignoring breaking. If you go significantly faster than the speed limit your far more likely to break at highway speeds. I'm not ignoring braking. Aggressive driving wastes a lot of fuel, but aggressive driving happens regardless of the posted speed limit. In fact, that rapid acceleration-brake cycle is more likely to happen when the flow of traffic is below the speed limit. > Further, IC cars often get better fuel efficiency by mixing slow acceleration periods at optimum RPM and coasting. (Car engines get ~10-30 efficiency based on usage.) You can do this manually, but it's hard. I don't think it's hard. It just requires paying attention to the traffic around you.
- Houshalter 10y ago
  Actually it's more to do with air resistance. It increases exponentially at higher speeds. You also don't burn less by driving really slow, since the engine burns some amount of fuel just by running at any speed. 40 mph is the sweet spot, supposedly. Driving at the speed limit will definitely save you more fuel than speeding.
  - vonmoltke 10y ago
    > Actually it's more to do with air resistance. It increases exponentially at higher speeds. You also don't burn less by driving really slow, since the engine burns some amount of fuel just by running at any speed. 40 mph is the sweet spot, supposedly. Actually, the sweet spot is dependent on the design and condition of the car. I'm not sure where exactly it is, but I think you are right that it is usually around 40. > Driving at the speed limit will definitely save you more fuel than speeding. How does a number on a sign affect how much fuel I'm burning? If, as you indicated, the sweet spot for my car is 40 but the speed limit is 30, how am I saving fuel by going 30 instead of 40? What if the speed limit is 65? If they drop it to 60 am I suddenly using more fuel? If they increase it to 70 can I now go faster without using more? The speed limit is totally irrelevant to fuel consumption.
    - Houshalter 10y ago
      Of course it depends on the design of the car, but 40 is an average. >How does a number on a sign affect how much fuel I'm burning? I never claimed that it would. I said "Driving at the speed limit will definitely save you more fuel than speeding.", which is definitely true. If you speed you are going faster and using more fuel.
      - vonmoltke 10y ago
        > I never claimed that it would. I said "Driving at the speed limit will definitely save you more fuel than speeding.", which is definitely true. If you speed you are going faster and using more fuel. That statement has nothing to do with the speed limit, though. It may be trivially true, but adding the speed limit ties an irrelevant variable to it. Speed limit is a semi-arbitrary number that has nothing to do with how much fuel a car uses and how efficiently it uses it.
- sliverstorm 10y ago
  I think you're being deliberately obtuse. For 99% of people, obeying the speed limit will result in slowing down, which is what your parent was alluding to.

Houshalter 10y ago

Self driving cars will almost certainly use much more energy than regular cars. It will reduce the cost of shipping by a lot, increasing the amount of things which are shipped. It will reduce the price of taxis a lot, so people will drive more. And it will make long commutes and road trips much more convenient.

toomuchtodo 10y ago
Maybe, but you're still limited by atoms not occupying the same physical space at the same time ("traffic", "congestion", etc). There's limited road to use, so you'll still hit finite limits; if limits are reached, congestion charges will be used to bring demand inline with roadway supply.
- Heliosmaster 10y ago
  ideally the throughput of highway would be increasing with self-driving vehicles: no need for start/stopping when they can drive at optimum total velocity.
- agumonkey 10y ago
  Yes but the swinging hours pattern will melt since cars are now decoupled from humans cycle. Freeing a lot of pseudo-space.