driving yourself to the same location is generally worse for the environment
Curious what this is based on, taking road construction, car ownership, etc into the calculation? Because as for fuel consumption clearly it depends - if you're a family, taking 1 car is generally going to be more fuel efficient.
The car is slower, and an order of magnitude less efficient. And efficiency matters -- there's a limit to how much energy can be sustainably spent, and if transportation is more efficient, we get to do more other things.
The only thing that matters for your car's carbon footprint is how much gas you use. So regardless of time, if you have more gas in the tank at the end of your trip, your carbon footprint is lower.
The faster you go, the more your fuel efficiency decreases. For the most part this is due to wind resistance, because there is a velocity^2 argument there(ie if you double your velocity, you quadruple your wind resistance). Your engine is also designed to operate more efficiently at certain speeds but that is less directly quantifiable than wind resistance.
So you might be able to get 40MPG while doing a steady 40 mph, but only get 20MPG when doing 80mph.
So if you need to go 40 miles, if you can do it at 80mph it will take you 30 minutes, and will cost you 2 gallons of fuel. If you do it at 40mph it will take you 1 hour and cost you 1 gallon of fuel. So in this contrived example the longer trip has a lower carbon footprint.
In the real world, there are rarely two parallel roads going exactly the same place but just with a different speed limit. Usually you need to drive out of your way to get onto a highway to make your trip go faster. On the other hand driving directly at a slower speed usually entails more starts/stops at traffic lights which eats into your fuel efficiency. Google is probably in a good place to answer the question of how fuel efficient is a given route because they have so much data about average speeds, accelerations/decelerations required/ etc.
The embedded energy of a second vehicle won't be made up for in a 10-20mpg improvement, except in very very niche cases.
The lifetime amount of fuel/electricity used by a vehicle generally accounts for only half of the total energy. The other half is in it's manufacturing and disposal/recycling.
And there's additional lost efficiency than just the mileage, because you're using twice the embedded energy and presumably aren't doubling the amount of driving you're doing.
Maybe rentals or sharing schemes work in some cases, but they present their own inefficiencies, like less than perfect allocation, and transferring vehicles back and forth for each switch.
But for the majority of cases, it's much more environmentally friendly to own one single vehicle that meets all of your needs, even if it's relatively inefficient.
The most efficient vehicle for any particular person is usually the one that's already been built. (Which is why cash for clunkers was actually a bailout with negative environmental impacts, despite its branding of improved efficiency.)
Practically this incorrect. When a car is in single or double occupancy (which is majority of cases) it will pollute more than a motorcycle one. Yes, a filled bus or car might be more efficient, but the average utilization on an auto is very low since most people drive them alone.
But < 5 mile local errands are much more polluting per mile than longer trips though as the engine doesn’t heat up to an efficient temperature so it uses something like 4 times as much fuel per mile.
I don't see how that's relevant. If it were true that driving is more energy efficient than walking, then if all you cared about was energy efficiency, you'd prefer to drive the shorter distance, assuming the result holds even when driving short distances (which it very well may). (Though the author of the article is suggesting instead that you may want to somehow increase the energy efficiency of walking by more efficiently producing food.)
By reducing usage, you could have both vehicles last almost twice as long, so I think it's safe to directly offset the pollution from gas creation and combustion, making a second vehicle a very good idea from an environmental standpoint. Plus, parts from a vehicle can be recycled or reused, whereas fuel burns once.
Really though, it probably depends how long your commute is.
Interesting thought, but does it change anything? Each vehicle is still driven the same # of total miles and the same number of annual total miles are driven, so I'm not sure if the resulting carbon output is any different.
Some buses are more fuel efficient than average; so are some cars.
I was not promoting specific numbers; the point is there's a tradeoff and a tipping point where more trips make things worse, whatever the numbers are.
Averages have a way of being a lot lower than peak numbers, too.
The problem that this is the wrong measure to use emissions per mile, when it's really about emissions per trip.
A car flying down the freeway uses less emissions per mile, but if one is traveling 50 miles versus just walking to down the block the former is using a lot more emissions even if it is more efficient per mile.
Wouldn’t this cause more pollution? Lower fuel efficiency, increased congestion, more half-clutch inching, more stopping, more time spent by each vehicle on each road…
…At least assuming the number and routes of travels stay constant.
I used to drive a 2010 Diesel VW Golf, about 55kW, in Central Europe. It would take 4l/100km at 70kph and closer to 11l/100km when maneuvering slowly. 2.75x pollution diff per km in these scenarios.
Sound is important, but cars also pollute the air.
If car A produces 1 tons of emissions to build, and 100 tons over its life, and car B produces 2 tons of emissions to build, and 50 tons over its life, car B is the better one for the environment. (52 < 101)
Looking at emissions to build as a metric by itself is disingenuous, you should look at lifetime emissions instead.
Curious what this is based on, taking road construction, car ownership, etc into the calculation? Because as for fuel consumption clearly it depends - if you're a family, taking 1 car is generally going to be more fuel efficient.
reply