# Talk:Energy efficiency in transportation

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## Hot Air Balloons

I see that the NASA launch-site crawler is extremely fuel hungry. However for human transport hot air balloons may be the most fuel inefficient. The typical balloon will use 20-30 gallons of propane to travel 5-10 miles. A balloon may carry a small number of passengers, but would still be very inefficient per passenger mile.Flight Risk (talk) 01:02, 31 July 2016 (UTC)

## Major Oversight

The article is making a mistake by neglecting time. Imagine there are two identical cars that only differ in their engine. One car gets 50mpg @ 50mph. The other car gets 50mpg @ 100mph. Which is more efficient?

Fuel efficiency encompasses more than fuel per distance traveled. It must also encompass the time taken to travel that distance. In other words, conventional "fuel efficiencies" are not comparable between different velocities. A bicyclist getting "600 mpg" is probably not more efficient that an airliner getting "60mpg". What efficiency would the cyclist have at Mach 0.85?

The question seems absurd because a bicycle is several orders of magnitude less efficient than an airliner. A major source of inefficiency on the bicyclist and airliner is aerodynamic drag. A bicyclist has a drag coefficient (Cd) much greater than an airliner. Air drag increases at the square of velocity and linearly with air density. A bicyclist travelling at Mach 0.85 would require an absurd amount of power. Racing motorcycles are much more streamlined and have over 250x the power available, yet even they struggle to reach Mach 0.3.

Despite the bias against air travel, it is probably the most fuel efficient form of transportation used by the masses. Without considering the time component, the comparison of "fuel efficiency" in transportation is meaningless. — Preceding unsigned comment added by LostCause (talkcontribs) 07:11, 23 April 2011 (UTC)

I disagree that there is an oversight. This article is about the concept which most people call "fuel efficiency". You are right that a different measure that considers speed is also interesting, but it belongs in a separate article. I think the unit of "gallons per hour" is one of the most useful, because people make travel decisions based on how long it takes, not how far it is. That means that MPG is very biased towards air travel, not against it. LachlanA (talk) 05:37, 29 April 2011 (UTC)
I totally disagree that there is an oversight. Rather, the unit of Miles/Gallon is a unit of fuel consumption, not efficiency, and so does not really have a place in the article except for general comparison. The proper measure of fuel efficiency is fuel used per set distance, or fuel use per passenger over set distance, or in general energy used per set distance (with or without pasenger). So, the appropriate measure for miles and gallons is Gallons/100 Mile, the amount of fuel used to cover 100 miles. In this case, the car which has 50mpg @ 100mph has 50Gallons/100 miles, and the car with 50mpg @ 50 mph has 100Gallons/100 Miles. Using appropriate measures of efficiency, we see that the actual distance traveled has no bearing on the efficiency of the transportation. RevZoe (talk) 21:21, 19 July 2011 (UTC)
I think you have it backwards. Miles/Gallon is a measure of efficiency. Fuel consumption is measured in Gallons/Mile. Hydradix (talk) 15:15, 17 September 2016 (UTC)
I too disagree that there's an oversight. You assume that time spent traveling is time wasted. Yet travel itself can be worthy. If something gets you somewhere twice as fast, that doesn't necessarily mean it's more efficient. It's only more efficient if the only consideration is arriving at the destination. Some might say that the journey is just as important as the destination, and for those people, a bicycle would be far more efficient in regard to time than an airliner. The worth (or negative worth) of time spent in travel is subjective. — Preceding unsigned comment added by Ianbrettcooper (talkcontribs) 12:14, 13 April 2012 (UTC)
Energy efficiency, fuel efficiency, fuel economy has never dealt with time, only the amount of fuel needed to an amount of work. The car that gets 50 mpg at 100 mph has done the same work as the car that gets 50 mpg at 50 mph. The fact that it does it faster is irrelevant in this situation. If that 100 mph car slowed to 50 mph then it may get 80 mpg (or whatever), at which point we can say it is more fuel efficient. If you bring time into the mix, you are talking time efficiency, and yes, an airplane or fast car will be more time efficient. True fuel efficiency should deal with passenger/distance/energy. According to https://truecostblog.com/2010/05/27/fuel-efficiency-modes-of-transportation-ranked-by-mpg/ You will find an interesting chart. Notice how a freight ship which gets 0.004 mpg is quite efficient if you are able to cram 77,000 passengers on board. Hopefully the bathrooms remain in service. Flight Risk (talk) 19:03, 3 October 2016 (UTC)

I realize that J/km (and similar units) are popular for describing energy-efficiency in transportation, but I think somewhere it should be pointed out that J/km (and similar) really measure inefficiency. Taking the lead section as an example, a bicycle with a few hundred J/km (hJ/km) is not less energy-efficient than a helicopter measured in MJ/km. In other words, the MJ/km helicopter is more energy-inefficient than the hJ/km bicycle. Please correct me if I'm wrong.

If that is true, then efficiency would be the inverse, right? Energy-efficiency = km/J ? This seems more logical to me (based on units), because then a more energy-efficient bicycle would be a few km/hJ (10 m/J) which is obviously greater than a km/MJ (mm/J) helicopter... I mean 10 m/J is obviously (I hope) more energy-efficient than 0.001 m/J.

I'm not literally suggesting we change the title of the article, because we can't change the popular/common use of the term/concept/unit. But shouldn't this fact be mentioned somewhere? I don't have any sources to back me up, and I'm not an expert so I didn't edit anything myself... and obviously I have a very poor way of expressing the idea. But can we agree this issue needs to be addressed somewhere in the article, to help people new to the topic understand why smaller values are more efficient? I think I would be confused if I wasn't already familiar with the topic...

Just had an idea: maybe in the lead we could mention more intuitive units, like km/L or mi/gal, and then mention that energy efficiency is also commonly, but misleadingly, measured in reciprocal units, like J/km. How does that sound? Hydradix (talk) 15:15, 17 September 2016 (UTC)

## broken link to us energy guidebook

maybe someone with more time can follow up on this...

I don't have the time to find all the references & correct them but i went looking for this reference, which is cited at least twice.

edition 28 appears to be gone, edition 30 is available at: http://cta.ornl.gov/data/index.shtml

US government-produced data should be reproducible so perhaps a copy should be downloaded to wikipedia for future reference.

## data

best case samples

• best 4-seat car : peugeot 208 1.6 litre BlueHDi, NEDC 3.0 litres per 100 kilometres (78 mpg‑US) [1] : 0.75 L/100 km per seat
• best 5-seat car : peugeot 308 1.6 litre BlueHDi, NEDC 3.1 litres per 100 kilometres (76 mpg‑US) [2] : 0.62 L/100 km per seat
• best 7-seat car : Citroen Grand C4 Picasso e-HDi 90 Airdream, NEDC 3.8 litres per 100 kilometres (62 mpg‑US) [3] : 0.54 L/100 km per seat
• best 9-place minivan : Renault - Trafic III - 1.6 dCi, NEDC 5.7 litres per 100 kilometres (41 mpg‑US) [4] : 0.63 L/100 km per seat

Greyhound Canada fuel consumption : 110 kilometres per litre (0.91 l/100 km) per passenger ("Facts & Figures". Greyhound Canada.)

## Jet Pack

Can a reference for a jet pack be located? 132.188.71.5 (talk) 00:34, 25 August 2015 (UTC)

The Bell Rocket Belt goes 250 m on 19 litres of hydrogen peroxide. There is a table on the article page but it doesn't seem to be sourced. Kendall-K1 (talk) 23:25, 10 August 2016 (UTC)

## First image is NOT representative

The first image - a truck - is NOT representative of efficiency! Trucks are simply not an efficient mean of transportation. Seems to me more commercial, like Tesla. 145.64.134.245 (talk) 11:55, 26 August 2016 (UTC)

I don't think there is anything wrong with using a photo of a truck. This is not the "Most efficient modes of transportation" article. But the caption does seem overly promotional and a bit off-topic. And this brings up another point, most of what we have is consumption per passenger-km. There is very little on consumption per tonne-km of freight. We've got a number for trains but nothing on trucks except the photo. Kendall-K1 (talk) 12:31, 26 August 2016 (UTC)
I also just noticed that we have a photo of a Tesla, but nothing about it in the text. Kendall-K1 (talk) 12:38, 26 August 2016 (UTC)

## E-bikes

We could use a paragraph on e-bikes. So far I can only find manufacturer's claims, which I don't want to use. Kendall-K1 (talk) 12:36, 26 August 2016 (UTC)

## Analysis section

The Analysis section smacks of WP:OR. I am going to remove it unless someone wants to defend it. Kendall-K1 (talk) 05:58, 27 August 2016 (UTC)

## Updated intro

I updated the intro because it really annoyed me that the two common measures of transport efficiency (fuel economy and fuel consumption) were not clearly identified, although the article uses both! I provided reliable sources, but I never found an "official" definition of "efficiency in transportation". In fact, one reliable source (the state of New Jersey) considers "efficiency in transportation" as the number of passengers per vehicle (p/vh?).

Anyway, I want to point out that my edit was not original research! When I use the phrase "Energy efficiency in transportation is often (and confusingly) described in terms of fuel consumption" this is based on my cited source, and other sources not mentioned here (but I did list some of them in another article). In other words, Fuel Consumption is different/confusing from Fuel Economy is not just my opinion... other reliable sources agree.

Finally, I think my new intro now gives a decent general overview, and also summarizes the remainder of the article (efficiency per various modes of transportation). So, can we remove the "need to expand introduction" from this article? Hydradix (talk) 09:16, 18 September 2016 (UTC)

This has been discussed in the past but not much has been done. I think this is a step in the right direction. Kendall-K1 (talk) 12:38, 18 September 2016 (UTC)

## Composite table

I think, overall, this article gives a good description of energy efficiency (per vehicle). But upon review of the current article, I found it hard to compare various modes of transport (walking, bicycling, car, truck, train, airplane, etc.). I think a composite table would be VERY useful for the average reader... but if I did it, it would be original research (I don't know of a reliable second-party source). If anybody has a reliable source, we (at least me) would appreciate a "table of efficiency per vehicle"! Hydradix (talk) 10:22, 18 September 2016 (UTC)

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