The age of speed: how to reduce global fuel consumption by 75 percent

If we cut the average speed of all vehicles by half, fuel consumption would decrease by a whopping 75 percent.

Breaking speed records was an almost daily occurence throughout the 20th century. Cars, ships, planes and trains became faster and faster, year after year. Because the power needed to push an object through air increases with the cube of velocity, this race to ever higher speeds raises energy consumption exponentially.

Engineers treat velocity as a non-variable, while in fact it is the most powerful factor to save a really huge amount of energy - with just one stroke, at minimal cost, and without the need for new technology. Lower speeds combined with more energy efficient engines, better aerodynamics and lighter materials could make fuel savings even larger.

Picture : Mando Maniac

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"The fastest car in the world reaches 10 times the speed of a normal vehicle cruising the highway, but it consumes 550 times more fuel"

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Air resistance (drag) increases with the square of speed, and therefore the power needed to push an object through air increases with the cube of the velocity (see the formula here). If a car cruising on the highway at 80 km/h requires 30 kilowatts to overcome air drag, that same car will require 240 kilowatts at a speed of 160 km/h.

Thus, a vehicle needs 8 times the engine power to reach twice the speed. In principle, this means that fuel consumption will increase fourfold (not eightfold, because the faster vehicle exerts the power only over half the time).

Picture: The Brooklands Society Photo Archives

Over a distance of 1,000 kilometres, the slow car would consume 375 kilowatt-hours (12.5 hours multiplied by 30 kilowatts) and the fast car would consume 1,500 kilowatt-hours (6.25 hours multiplied by 240 kilowatts).

Speed is the key

However, this extra fuel consumption can be diminished or even negated by, most importantly, more fuel efficient engines, lighter vehicles materials and better aerodynamics. Even though today's cars are faster than those from decades ago, they consume a similar amount of fuel. This is the reason why almost everybody is talking about energy efficiency and aerodynamics, and not about speed. 

But if you lower the speed, fuel consumption is decreased by the full 75 percent. More efficient technology can not change that – unless in a positive way. If you combine a lower speed with more fuel efficient engines and better aerodynamics, fuel savings can become much larger than 75 percent.

Aerodynamics

Drag can be partly offset by better aerodynamics: a boxy car like the Volvo 740 has a drag area (drag coefficient multiplied by frontal area) that is almost twice that of the most aerodynamic standard car, the Honda Insight. The Volvo needs almost two times the engine power of the Honda when driven at 120 km/h.

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"A boxy car vehicle at 60 km/h will consume much less fuel than the most aerodynamic vehicle driving at 120 km/h"

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Picture : the Stanley - the fastest steamcar ever built.

Yet a Volvo 740 driving at 60 km/h will face less than half the drag and will need 4.6 times less energy power than a Honda Insight driving at 120 km/h. When compared to velocity, the potential of aerodynamics is limited.

Moreover, very good aerodynamics is incompatible with high speeds. Formula 1 racing cars have the worst drag coefficients of all vehicles on wheels, because of their large spoilers and very wide tyres. At higher speeds, it becomes important to minimize lift at the expense of better aerodynamics so that the car is not catapulted into the air. 

Low speed trains

The blindness for the importance of speed leads to doubtful conclusions, like the environmentally friendly label of high speed trains. The French TGV that set the most recent speed record at 575 km/h for wheeled trains in 2007 has an engine output of 19,600 kilowatts. A contemporary “slow” train like the Siemens ES64 with a top speed of 240 km/h has a maximum power output of 6,400 kilowatts.

Travelling 1,000 kilometres, the “slow” train will consume 26,240 kilowatt-hours (over 4.1 hours) while the fast train will consume 33.320 kilowatt-hours (over 1.7 hours). A real slow train (like this one from 1956 with a top speed of 120 km/h) would consume only 20,000 kilowatt-hours over the same trajectory (and would do this in 8.3 hours, comparable to the travel time of a car).

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"Technology can limit the growth of energy consumption, but if we want to lower energy consumption, we have no other choice but to adapt speed"

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Picture: The Brooklands Society Photo Archives

The French high speed train is definitely more energy efficient than the Siemens locomotive, and that one is definitely more energy efficient than the 1956 train, because in both cases power consumption did not increase exponentially (*) with speed.

But that does not take away the fact that the faster trains consume more energy than the slower trains. If, on the other hand, we would equip the 1956 train with the energy-efficient technology of today's high speed train, it would consume much less energy than it did 50 years ago.

Time is money

High speed trains are labelled environmentally friendly because they are not compared to other trains but to planes (A Boeing 747 would consume around 65,000 kWh over the same distance, over approximately 1 hour).

In a way this makes sense, because if a passenger prefers the fast train over the plane, he will consume less energy for a similar trip. He might not make that choice when the train would be much slower than the plane. On the other hand, if passengers that normally would take a slow train now prefer a fast train, high speed trains do raise energy consumption. The problem is that people see a shorter travel time as an advantage, while it has no ecological value whatsoever.

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"Travelling from A to B would require twice as much time. But global world oil consumption would be halved"

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Picture : Agence Eureka

You could as well argue that airplanes are green because they consume less fuel than rockets. This sounds ridiculous now, but if rocket planes take off, their inventors will no doubt claim that their toys are environmentally friendly because they go faster than airplanes but consume less than rockets. Technology alone can limit the growth of energy consumption, but if we want to lower energy consumption, we have no other choice but to adapt speed.

Fixation on technology

A decrease of 75 percent in fuel consumption is not peanuts. More than 60 percent of world oil production is used for transportation, which means that total oil production would be almost halved (-45%). In combination with more efficient engines, better aerodynamics and lighter materials a 75 percent reduction of oil production is not unrealistic.

Yet, when the International Energy Agency argues that the average car sold in 2030 would need to consume 60 percent less fuel than the average car sold in 2005, it claims: "With current technologies, only plug-in hybrids are capable of this”.

This statement is wrong. We could lower the fuel consumption of cars (and other vehicles) by at least 75 percent, we could do it today, and we can do it with present technology. 

© Kris De Decker (edited by Vincent Grosjean)

Comments (25) / Subscribe to feed or email

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Article continues below:

Part 2 : breaking the hull speed and the sound barrier

Part 3 : the fastest "train" does 10,000 km/h

Part 4 : wind and human powered vehicles are setting speed records, too

Picture: The Brooklands Society Photo Archives

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Wave drag, sound barrier and hull speed

At extreme high speeds, the link between velocity and power consumption becomes even more defined. Here, wave drag enters the picture and drag increases more. This is the reason why commercial airplanes never fly faster than an average speed of about 900 km/h (except for the retired Concorde). If they would go faster than 1.200 km/h, they would break the sound barrier at the expense of a massive increase in power consumption.

The Thrust SCC (pictured left), the car that holds the land speed record of 1,228 km/h, and thus broke the sound barrier, consumed 5,500 litres of fuel per 100 kilometres. So even though its speed is only 10 times higher than a normal car driving the highway, the supersonic car consumes around 550 times more fuel. A picture collection of land speed record vehicles can be found here.

When travelling on water, a similar effect comes into play - albeit at much lower speeds. Every watercraft contains a speed barrier that is (mainly) dependent on the length of the ship and on the shape of its bow. This barrier (called the hull speed in layman's terms) can be crossed, but only at the expense of another exponential increase in power consumption.

This is why ships are so much slower than other kinds of transport, and why most fast ferries were retired. The fastest watercraft reached a record speed of 511 km/h - not even half that of the fastest car. Underwater drag is even worse: the speed record of  submarines is only 60 km/h.

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Planes on rails : 10,000 km/h

The fastest railed vehicle is not the TGV or the JR-Maglev, but an unmanned rocket sled that achieved a speed of more than 10,000 km/h. Rocket sleds are platforms on wheels, propelled by rockets and used to test missiles or (in earlier times) equipment for military aircraft. They do not use wheels but sliding pads which prevent the sled from flying from the track. The fastest manned rocket sled (pictured above) reached 1,017 km/h.

Some other remarkable manned rail vehicles were the American Pioneer Zephyr, the German Schienenzeppelin (which was powered by an airline propeller at the rear and held the speed record of 230 km/h for railed vehicles from 1931 to 1954) and the French Aérotrain (pictured above, source), a predecessor of the Japanese Maglev trains.

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Human & wind powered speed records

Human and wind powered vehicles are setting new speed records, too.  The fastest human powered watercraft is the Decavitator (with a record speed of 34.3 km/h), while the fastest wind-powered speed record was set earlier this year by windsurfer Antoine Albeau, who reached 90.9 km/h (see picture above, taken from Masters Of Speed). That's only 5 times slower than the fastest engine powered watercraft. A windsurf board has a much higher speed barrier since it has a planing hull (unfortunately not an option for everyday use, see this video). See also: Sailrockets & kiteboats.

The speed record of a pedalled land vehicle is 86 km/h, that of a pedal powered aircraft 32 km/h, and that of a human powered submarine 15 km/h (only 4 times slower than the record speed of an engine powered submarine). The speed record for normal bicycles was set at almost 50 km/h (on average during a 1 hour run). The fastest wind powered car does 188 km/h.

Most of these vehicles are not suited for practical use, but that's not the point. They prove that speed kicks are possible without burning many barrels of oil. More information at the Human Powered Vehicle Association.

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Speed records for manned vehicles 1900-2008

1900 : water (63 km/h), land (106 km/h), wheeled train (145 km/h), air (16 km/h)

1925 : water (141 km/h), land (235 km/h), wheeled train (210 km/h), air (448 km/h)

1950 : water (258 km/h), land (634 km/h), wheeled train (230 km/h), air (1079 km/h)

1975 : water (459 km/h), land (1015 km/h), wheeled train (331 km/h), air (3332 km/h)

2008 : water (511 km/h), land (1224 km/h), wheeled train (575 km/h), air (3530 km/h)

Source: Wikipedia List of vehicle speed records

Picture: a fighter jet breaks the sound barrier 

Below: the shrinking world (info here)

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Related articles :

• Trolleybuses and trolleytrucks : electric transport for a bargain
• Cleantech from the 1940s : the Citroën 2CV
• Viva Las Vegas : the energy efficiency paradox
• Life without airplanes : from London to New York in 3 days and 12 hours
• Who killed the electric grid? Fast-charging cars need power peaks of 150,000 watts
• Cargo ships, then and now : which one is the fastest?
• Wood gas vehicles : firewood in the fuel tank

• Cars - out of the way : imagine bicycles taking over the motorways
• How (not) to resolve the energy crisis: first things first
• Planes on wheels : how eco-friendly is a high-speed train?
• The Kalakala : the art of (slow) travel
• Sailrockets & kiteboats
• Green slow air cargo : airships
• Water powered cable trains : up and down the mountains without energy
• Only idiots travel by train : how can you blame people for flying if there is no affordable alternative?

Above : the Japanese high speed train JR E 4, source: Hochgeschwindigkeitszuege

Comments

[Morten Lange]

(26)

gurusid : It seems to me that some of your assumptions are false.
1. You talk about congestion as if that was a product of driving at low speeds. In fact it is the other way round. Lower speeds begets better throughput and more flow in city traffic.
2. You seem to imply that if at high speeds you do not need to accelerate as often. This skewed proposition is probably caused by people driving at really high speeds primarily on highways. There large amounts of money have been spent on an inefficient means of transport, not being paid for by the users. Additionally : close to urban centres and in many other places,if infrastructure and las allow speeds to be high, that increases the competitive advantage of cars over other more efficient modes like buses, trains, bicycles and walking, thus reducing the overall efficiency of the system.

It should be evident that it is the efficiency of the transportation system that matters, not the individual vehicle.
But of course the efficiency of individual vehicles are important factors. Especially when considering the effects of mode shifts to more efficient means of transport away from the car. A transportation system where the modal fraction (modal split) of public transport rises, or the modal fraction of bicycles rises will be improving energy efficiency, and generally reducing pollution, given that other things remain unchanged. But no matter what speed cars run at.

[gurusid]

(25)

Hi Folks, Interesting article. As I currently understand it for the ICE (internal combustion engine), the optimum speed is about 55.6mph (about 90kph). This is due to the compromise between vehicle weight, energy use and drag coefficients. At low speeds you encounter the main problem of engine run time and inertia - especially starting from standstill. At higher speeds the drag takes over. Thus one ends up with an average efficiency curve for the current vehicle fleet (mpg/energy/pollution) that has its maximum point at about 55mph (90kph). This varies drastically when looked at on a per vehicle basis - see for example this 'random' test: http://www.metrompg.com/posts/speed-vs-mpg.htm The 'Pontiac firefly' test cruising in top gear at 30mph might be good for fuel consumption, by it will play hell with you main bearings! Also, to implement the savings mentioned above, one would have to not just lower the ex-urban speed but also raise the intra urban speeds or stop these journeys altogether as many (i.e. driving down to the shops) are less than a few miles (I know this varies depending of where you live) but for an average EU city: Table 1 Average trip length distribution for the city of Antwerp Distance (km) Trips (percentage) less than 1 ... 7.68 1-2............ 15.21 2-3............ 12.97 3-4............ 9.69 4-6............ 14.73 6-8............ 10.69 8-10............ 6.00 10-15........... 6.17 15-20........... 1.33 Greater than 20... 15.53 From: C. Mensink,I. De Vlieger, & J. Nys, 2000, "An urban transport emission model for the Antwerp area" Published in: Atmospheric Environment 34 (2000) 4595}4602 Another point is that emissions of CO2 are in fact a better indicator of fuel used than energy. This is because the CO2 relates more directly to the fuel used than does the energy produced. For instance, at lower speeds proportionally more energy goes into running the engine and ancillary equipment than towards moving the vehicle - hence the problem of high pollution levels in traffic congestion with all those idling engines and stationary/very slow moving vehicles. Systemically reducing high speed on long journeys will have an impact, but for intra-urban driving/fuel use, it will have to be a case of abstinence - over 60% of urban journeys are under 6k! That’s under 3.75 miles!!! Best Wishes, Sid

[LaGaffe]

(24)

"Moreover, very good aerodynamics is incompatible with high speeds. Formula 1 racing cars have the worst drag coefficients of all vehicles on wheels, because of their large spoilers and very wide tyres. At higher speeds, it becomes important to minimize lift at the expense of better aerodynamics so that the car is not catapulted into the air."

That's a lot of bunk. To go fast on your average grand prix circuit you have to be able to corner fast and most of the aerodynamics of a F1 car is designed to keep the car on the track (the downforce – downwards lift – generated exceeds the weight of the car). To go fast straight ahead (or on a banked track) you only need enough downforce to avoid taking off (compare an F1 and an Indy 500 car). Good aerodynamics is not the same as minimzing drag at all costs: it could be, as in the F1 case, to minimize drag for the required downforce.

(And even at bicycle speeds, aerodynamics makes a difference – ask Greg LeMond ;-)

[DanFoster]

(23)

One problem not brough up is article is that existing vehicles are designed for fuel efficiency at 80 to 100 km/hour. Driving existing cars at 50km/hour, actually gives a worse fuel efficiency. The entire engine, gearing, drive train and wheels width and other things would have to be redesigned if you want 50km/hour to be the most fuel efficient speed.

Cars are desinged so that 80 to 100km/hour are the most fuel efficient other wise, like the article suggests, you would burn 5x as much fuel driving at 100km/hour than at 50km/hour. No one would buy a car that burns a good 5L per 100km at 50km/hour, but then burns 30L per 100km at 100km/hour. So instead the cars are made to burn about 10L per 100km/hour at nearly all speeds 100km/hour or lower.

That is the exact reason why hybrid cars work - even though they are still only powered by fuel (the battery is charged by fuel). The battery allows the car to operate at extremely high efficiency at lower speeds, while still allowing the car to reach 80 to 100km/hour. Obviously the hybrids by definition will be slower at highway speeds, as they have to convert fuel to electricity first (energy loss) as well as burning fuel directly.

I still think its a good idea to reduce speeds to 60km/hour. But it will never happen, because it would require all existing cars and trucks to be dropped immediatly, and it would have huge implications for the world in general. For example property prices and zoneing of land is done largly on the fact that the majority of the population will travel only around 1 hour to work. So if you decrease the top speeds to 60km/hour you will reduce significantly the area in which people will consider a 'city' or 'urban' area, forcing everyone to live even closer together.

[Stephen w]

(22)

you could travel at 4000 mph and use virtually no energy - just transport a dollop of it from your starting point to your destination - see evacuated tube transport http://www.et3.com/

[Robin 'Roblimo' Miller]

(21)

I cut my commute 75% by moving from a house where my home office/studio was in a separate building to one where it's in an enclosed porch built onto the main structure.

We also gutted the new place (a small house trailer) and insulted hell out of it. Our electric bills are now ~$70/month Spring and Fall, ~$90/month during (hot Florida) summers with a/c running, and between those figures in the winter, with electric heat.

But in the spirit of this article, when I am cruising the neighborhood in the future I will ride my bicycle slower -- to save fuel, not because I'm getting old. :)

[Roland Smith]

(20)

Since 2007, the hour record for pedal powered land vehicles stands at 87 kph: http://www.ihpva.org/hpvarec3.htm#nom27

The absolute speed record (200 mtr flying start) stand at 130 kph: http://www.ihpva.org/hpvarec3.htm#nom01

The world speed record for the fastest aircraft still belongs to the X-15, 7272 kph (4519 mph): http://en.wikipedia.org/wiki/X-15

[Myrtone]

(19)

Hi Claude,

Calling them nazis isn't funny, are they in anyway racist, let alone anti semitic?

[Dr. Claude Miller]

(18)

If most of you Speed Nazis were to run around the block, breathing through a small straw, we wouldn't have to deal with you pansies anymore.

[Kris De Decker]

(17)

If you manufacture cars with a maximum velocity of 60 kph, nobody would exceed the speed limit.

[MBM]

(16)

The figure of 60kph was mentioned in the article as a proposed speed limit. If this was a recommendation for cross-country travel then it is decidedly not to be taken seriously. That is less than 40mph which would take us back to the average over the road speeds of the 1920s. This will not happen. Period. Even the 55mph limit of decades ago was widely flouted and served chiefly to enrich the coffers of speed-trap happy municipalities and radar detector manufacturers. The current interstate limits of around 70mph are considered reasonable by most people and are not exceeded to remotely the same degree as was the 55mph limit. Cutting speeds from 70 to under 40 would result in an entire nation of traffic scofflaws as virtually no one would obey such a ridiculously low limit however much fuel it would save. This would amount to a prohibition of timely cross-country travel. We all know how well Prohibition worked out. Such low limits would be wildly unpopular with 98% of the driving public and so would be promptly repealed in the unlikely event they were ever imposed in the first place.

Current technology can build vehicles that get much better mileage at 70 than current vehicles resulting in real gains because most of the driving public would be unlikely to go any faster than they already do. Even exoticars can only use their high speed potentials for very short distances and their tiny numbers on the road do not affect the overall picture anyway. In any case even if by some miracle passenger vehicles could be built that could get 70mpg at 120mph it is extrememly unlikely that interstate speed limits would be significantly increased because the roadways simply are not designed for much higher speeds. Most drivers aren't designed for it either.

[g569]

(15)

Want to cut your commute time to about one minute each way, regardless of distance?

Telecommute.

Kitchen table to home office desk, log in, and you're there. I designed one of the bits that makes the telephones work. It's now in a PBX platform that is available worldwide. I'm not going to engage in crass self-promotion by mentioning brand names.

Know what? Methane has started bubbling up from under the Arctic sea. Anyone else here see the news? Know what that means? It means say ByeBye to the human race unless we turn the whole damn situation around pronto.

Oh, and as for automobiles with 200 - 300 horsepower. That's the kind of power you need for a fully loaded tractor trailer, or for one of those gigantic rotary snow plows that will clear a 12 foot (four meter) swath of snow that's six feet (two meters) deep on an airport runway.

The idea that anyone would have an engine like that in an automobile is so insane that if we can't kick that habit, we friggin' *deserve* to go extinct in thirty years.

[ecoangel]

(14)

Slower is not always better - much depends on gearing, weight, Cd, rolling resistance etc.

I agree with you that today's cars are far too heavy and inefficient. I drive a car that came out in 1999. The Audi A2 1.2 TDI that can run on bio diesel. It produces 81g/km CO2 on dino fuel and can return 3L/100km even with 4 adults on board with luggage! But look at Audi now! They stopped making the A2 in 2005 and now make monsters like the Q7 SUV.

Their lightest car is the overweight A3.

As for the Prius - well more needs to be written about that Toyota marketing ploy. Not bad around town but on the highway the MPG is not as good as a std diesel car.

[Ben]

(13)

Tim,

Sure it would take twice as long on the road for a trip of a given distance, but who wants to take twice as long traveling. People would move closer to work.

You should retract you statement about dumb ideas. This site is filled with innovative and interesting ideas. Some of them may be more like thought experiments than actually being practicable, but it is still a very valuable resource.

[Kris De Decker]

(12)

Yes, David, you are right. I should have taken a lower value to make the comparison more realistic. But that does not make the comparison wrong.

[David]

(11)

While I understand the arguments made here, would you please get your facts straight - how many cars can you think of that require 240KW (321 horsepower) to reach 160km/h (100mph)??? My car is an average size saloon car and has only 92KW (123 horsepower) and it is well capable of cruising at over 200km/h (112mph)!

[kdd]

(10)

Some interesting comments here, too:

http://www.treehugger.com/files/2008/09/reduce-fuel-consumption-cut-speed.php#comments

[George Seldes]

(9)

Actually, when you factor human behavior in, power consumed DOES follow the cube of speed, with no need to reduce for the reduced time because distances AREN'T constant, at least not in N. America --- by which I mean that the first thing a North American does when offered a faster travel option is compute how much further he/she can live from where they routinely travel. So rather than at least compensating for the higher energy consumption rates by keeping the distance travelled the same, the Homo Non-Sapiens North Americanus will sprawl further and further out, as if impelled to keep total travel time at a certain level.

[Wes]

(8)

That's really my point - there is no way to set a speed limit in the name of fuel efficiency. I'm not advocating pushing speeds beyond diminishing returns - the market cost of fuel and technology imposes that limit already, hence the reason WHY we have no commercial supersonic jet. However, technology keeps moving the needle on the diminishing return point, and there's no reason not to take advantage of it. In your article, you even said that the faster train was more efficient than the slower train. As technology evolves, we come up with ways to make things go faster with less fuel used than the simple square of the velocity rule. Until we run up against the point where no amount of technology will make a commesurate increase in speed more efficient, there's no benefit to reducing speed beyond what is cost-effective.

[Kris De Decker]

(7)

You make some interesting points, but in your conclusion you state that we need to provide a transport system "at the speeds and capacities necessary to make it attractive to the largest number of people that it can support and remain more efficient than the alternatives."

Could you put an exact speed limit on that?

Because if I look around me, cars and motorcycles are getting faster and faster. The speed limits don't change, but the machines and therefore also the drivers do.

This "necessary" speed you are talking about keeps climbing all the time, so where do you set the limit? If you don't do that, fuel consumption will keep growing, regardless of all energy efficient technology.

The guys you see on those pictures in the article, were racing at speeds that we now consider normal.

[Wes]

(6)

With everyone rushing to build windmills and solar farms, does it really matter whether we use more or less electricity to make a faster train? Perhaps the better solution is to ensure that at least 75% of the power comes from a clean source. I follow you for other fossil-fuel powered devices, but even that is simply a matter of time before we can find an alternative that makes the argument largely moot.

However, take your time is money discussion a bit further, and it becomes a relatively direct economics case study - a complex one, but it definitely becomes about utility vs cost. I don't think that people necessarily view faster things as having no ecological value (positive or negative) as much as this: they do not view the ecological negative as so much incrementally worse that it's more valuable than their time. For example, I like spending time with my family more than I like spending 1-3 hours commuting. From an environmental perspective, I would gladly accept any mode of transportation that would cut my commute time by 75% even if it was powered by coal, diesel, baby seals and virgin rainforest timber. I might think twice if it meant increasing the cost of my commute by 75% as well. This is the same decision some folks have made about transitioning to public transit or a bicycle in the world of expensive fuel - what is my personal cost threshold for the convenience of speed? Yes, environmental impact may help to break a tie between two things that are so close that they may as well be equal, but I don't believe that it's the primary decision factor in most people's lives.

Your argument about fast trains vs slow trains v planes is simplistic, because if there are multiple transportation alternatives, people will choose the fastest one within their means. The only way to ensure that people always choose the most ecologically friendly method of transportation for their person or goods is to put a price on each method based on its environmental impact. This may be different for each person and each situation, since it might be better for me to drive my car 2 miles to the store instead of needing a bus route that only services me and my neighbor, since my car is more fuel efficient at that speed and capacity. So unless all transportation pricing is set by a central authority with a big supercomputer that can run the numbers on each trip for each person, rather than oh, say, by capitalism, this is one of those things that we're going to have to run based on least common denominator. That is, make transportation as efficient as possible at the speeds and capacities necessary to make it attractive to the largest number of people that it can support and remain more efficient than the alternatives.

[Kris De Decker]

(5)

Maybe if cars go only 60km/h people would realise that on many occasions a bike or a train is a better alternative.

Maybe we can bring back the speed of cars to 30 km/h and keep the trains running at 180 km/h...

[Tim Rosencrans]

(4)

Dumb ideas seem to be flourishing these days. Transportation systems do not exist of only cars. Cars need roads. If all cars go at half speed then traffic is doubled. This is simply not doable in most areas.

Exactly how efficient is a car stuck in a traffic jam?

[Kris De Decker]

(3)

I think your car is more efficient on the highway because it cruises at a constant speed, without much braking and accelerating.

That said, it is true that our vehicles are optimized for higher speeds than those I am aiming for, and thus might not give the fuel savings I am calculating here.

So in order to achieve the full 75 percent, we need a new generation of cars (no new technology, just a downsized version of what already exists). With cars this is easier to achieve than with ships or planes, which have a much longer service life.

I am not against hybrids, but they should be combined with lower speeds. And yes, electric cars are more efficient, but then you have to lower speeds anyway otherwise your autonomy will be very limited.

[Jinx]

(2)

My car doesn't run on kilowatts, though.

And how is it that cars, according to the EPA rated numbers, are MORE efficient at highway speeds than 'city' speeds (e.g., 17 city/24 highway) except of course, hybrids, which are a NEW design technology that makes them more efficient when in stop and go traffic? In that model, it would be more efficient for cars to never go under 55mph!

Granted, you talk a lot about trains in your article, and yes, on an unobstructed track, traveling at a steady speed, a vehicle can have more efficiency than anywhere else.

If the automobile industry ("The Big Three") had not buried "Smokey's Engine", automobiles would run at greater than 75% efficiency! And what other technologies has their collusion with "Big Oil" hidden from the innocent public?

[Kris De Decker]

(1)

Ahum, thanks to joaquintides at reddit who immediately noted that a decrease of 400 percent is impossible. A fourfold decrease (what I meant to say) = 75 percent.

http://www.reddit.com/r/energy/comments/70vwk/the_age_of_speed_how_to_reduce_global_fuel/