Fuel Efficiency: Modes of Transportation Ranked By MPG

Building on a previous post on the energy efficiency of various foods, I decided to create a list of transportation modes by fuel efficiency.  In order to compare vehicles with different passenger capacities and average utilization, I included both average efficiency and maximum efficiency, at average and maximum passenger loads.

The calculations and source data are explained in detail in the footnotes. For human-powered activities, the mpg ratings might appear high, but many calculations omit the fact that a human’s baseline calorie consumption must be subtracted to find the efficiency of human-powered transportation. I have subtracted out baseline metabolism, showing the true efficiencies for walking, running, and biking.

For vehicles like trucks and large ships which primarily carry cargo, I count 4000 pounds of cargo as equivalent to one person. This is roughly the weight of an average American automobile (cars, minivans, SUVs, and trucks).

The pmpg ratings of cars, trucks, and motorcycles are also higher than traditional mpg estimates, since pmpg accounts for the average number of occupants in a vehicle, which according to the Bureau of Transportation Statistics is 1.58 for cars, 1.73 for SUVs, minivans, and trucks, and 1.27 for motorcycles.

List of Transportation Modes By Person-Miles Per Gallon (PMPG)

Transport Average PMPG Max PMPG
Bicycle [3] 984 984
Walking [1] 700 700
Freight Ship [10] 340 570
Running [2] 315 315
Freight Train [7] 190.5 190.5
Plugin Hybrid [5] 110.6 350
Motorcycle [4] 71.8 113
Passenger Train [7] 71.6 189.7
Airplane [9] 42.6 53.6
Bus [8] 38.3 330
Car [4] 35.7 113
18-Wheeler (Truck) [5] 32.2 64.4
Light Truck, SUV, Minivan [4] 31.4 91

[0] I used these conversion factors for all calculations.

[1] Walking: A typical person expends roughly 75 calories to walk a mile in 20 minutes. An American burns about 30 calories just to exist for 20 minutes, so the net expenditure for walking is 45 calories per mile. One gallon of gasoline contains roughly 31,500 kcal, so 45 calories is 0.0014 gallons of gas. Thus the average American has a walking efficiency of 700mpg. This estimate is higher than that given elsewhere – the crucial difference is that you have to subtract out baseline metabolism, since an American consumes over 2100 calories a day just to stay alive.

[2] Running: The calculation is similar to [1]. Here we assume a 6 minute/mile pace, which burns 1088 calories per hour, or 109 calories per mile, and 100 net calories per mile. 100 calories is 0.003 gallons of gas, for a fuel efficiency of 315mpg.

[3] Bicycles: Bicycling at 10mph requires 408 calories per hour, or 40.8 calories per mile, which is 32 net calories per mile. This yield an mpg rating of 984, higher even than walking!

[4] Automobiles: The Bureau of Transportation Statistics has done the heavy lifting for us, calculating BTU per passenger-mile for cars, light trucks, and motorcycles. For cars, the latest (2008) data point is 3501 BTU / passenger-mile, or 0.028 gallons per passenger-mile, which equals 35.7 pmpg (BTS assumes 1.58 passengers on average, so this equates to 22.6 mpg). Using the same BTS data, average pmpg for light trucks is 31.4, and for motorcycles is 71.76. For max pmpg, we use a max passengers of 5 for cars and trucks, and 2 for motorcycles. To do this calculation from the BTS data, we first divide the avg. pmpg by the avg. passenger count, and then multiply by the max in each case.

[5] 18-Wheelers: For 18-wheel rigs, BTS data shows an average diesel mpg of 5.1. This equates to a gasoline mpg of 4.6, using 125,000 btu / 138,700 btu as the gas / diesel energy ratio. The weight limit for trucks on most roads is 80,000 lbs, of which 55,000 might be the max load given a truck weight of 25,000 lbs. To convert load to passengers, I assume 4000 lbs per passenger, since that’s roughly the weight of a passenger vehicle. A 50% (average) loaded truck counts for roughly 7 passengers, and a full load counts for 14. Using these factors, average pmpg is 32.2 and max pmpg is 64.4.

[6] Plugin-Hybrids: With the exception of the Prius Hymotion conversion, plugin hybrids like the Chevy Volt have yet to reach market, and have not yet had a final mpg designation. Consumer Reports achieved 67 mpg with the Hymotion Prius, though Hymotion and many owners claim 100 mpg is possible. Using 70 mpg, and adjusting this by the 1.58 average passenger count, the Hymotion Prius has an average pmpg of 110.6, and a maximum pmpg of 350.

[7] Trains: While all trains have similar underlying efficiencies, passenger trains in the US are much less efficient in practice because of poor utilization. BTS calculates Amtrak efficiency at 1745 BTU per passenger-mile, which equates to 71.6 pmpg. Amtrak traveled 267 million car-miles in 2007, which equals to 16 billion potential passenger miles if the average car holds 60 passengers. In 2007 Amtrak consumed 10.5 trillion BTU of fuel, or 659 BTU per available passenger mile. Amtrak’s max pmpg is therefore 189.7 (if somebody would just ride it).

Freight trains consume 328 BTU to move a ton one mile. Using 4000 lbs of freight equals one passenger, this equals 656 BTU per passenger-mile, or 190.5 pmpg.

[8] Buses: At average passenger loads, buses achieve 3262 BTU per passenger-mile, or 38.3 pmpg. Per BTS data, buses average 6.1 diesel mpg, or 5.5 gas mpg. With a full load of roughly 60 passengers, a max pmpg of 330 is possible. The huge difference in average and max pmpg implies that buses are usually almost empty – perhaps smaller mini-buses should be used by more fleets.

[9] Airplanes: Airplanes flying domestic routes average 2931 BTU per passenger-mile, or 42.6 pmpg. The overall domestic load factor in 2008 was 79.6%, so at max capacity a plane might achieve 53.6 pmpg.

[10] Ships: In a previous post I found that shipping over water (by barge) costs one-third of shipping by rail. This implies that water based shipping is also roughly triple the efficiency in energy terms, since energy is one of the key cost drivers in transportation. This provides a rough estimate of 570 pmpg. According to this post, the world’s largest container ship travels 28 feet on a gallon of residual fuel oil (149,690 BTU or 1.2 gallons of gas). This equals 0.004 mpg. Per Wikipedia, the ship can carry 11,000 14-ton containers, or 77,000 passenger-equivalents using our 4000 lb conversion rate. Thus pmpg is 340 for this ship.

Fuel efficient vehicles to the rescue!

The market is responding to energy prices with a raft of new fuel efficient commuter vehicles. I thought I’d mention a few here – many of these vehicles or modifications are competing for the X-Prize, and a few, like Hymotion’s BREM for the Toyota Prius, are available today. The automotive market is changing fast, and 100 mpg looks like it will become a realistic target for drivers in the next few years! Where available, each model’s projected cost, mileage (for commute purposes), and top speed are provided.

Available Today:

Hymotion BREM for 04-08 Toyota Prius – $9995 (plus the price of a Prius), 100mpg, 100+ mph top speed. Hymotion’s battery-range extender module converts a standard 46mpg Prius into a 100mpg plug-in hybrid for under $10,000, and is available today in a handful of major cities.

Tesla Motors – $100,000, 200mpg, 140mph top speed. You can have a high-performance electric car today that costs 2 cents per mile to drive, if you’ve got 100k to burn.

Available by 2010/2011:

Chevy Volt – Exact details unknown (more here), but GM is aiming for a 2010 release of the plug-in hybrid Volt, which will have an all-electric range of 40 miles, and effective mpg of 100+ when used as a commuter vehicle.

Phoenix Motorcars’ Electric Truck – $47,500, 100+ mpg (exact figure unknown), 100mpg top speed.  Phoenix has developed all-electric truck and SUV models that it is currently selling to fleets, and will release to the public in 2010.

Poulsen Hybrid – Poulsen is developing a conversion technology which can be installed on the rear wheels of any vehicle to turn it into a hybrid.

Nissan has announced work on an electric vehicle with a 2010/2011 delivery date, but few details are available.

Toyota is working on a plug-in version of the Prius with a 2010 deliver date as well.

Small Commuter Vehicles: Most available in 2009-2010

GreenVehicles Triac – $20k expected price, 200+ effective mpg, 80mph top speed, and 100 mile range. The Triac is a three-wheeled commuter vehicle designed to help urban commuters park their larger vehicles during the daily grind.

Aptera – $30k, 230mpg, 85mph top speed. Another three-wheeled vehicle, Aptera looks more like a plane than a car, but still has two seats plus space for a child car-seat in rear.

Venture One – $20-25k, 100+ mpg, 100mph top speed. This three-wheeled commuter vehicle looks more like a motorcycle, and incorporates technology that enables it to automatically “lean” as it moves through curves.

Commuter Cars – Tango T600 available today for $108k, T100 target of $20k, 100mpg+, 120mph+ top speed. George Clooney owns a T600, whose tandem seating allows for two passengers or a rear child seat.

Fuel Vapor Ale’ – $75k, 92mpg achieved to date, 100mph+. This is another three-wheeled commuter car, but it’s shaped a bit like a rocket and is designed for high-end performance.

This list is not exhaustive, though I believe I’ve covered most of the credible efforts currently afoot. Feel free to add others in the comments below if you feel they were erroneously omitted.

Obama & McCain: Here’s a real way to reduce gas prices!

Oil prices have continued their steady march, breaking through $135/barrel (which implies gas around 4.25) and climbing. As noted previously, the fundamentals driving oil prices higher are steady growth in global demand for oil combined with flat supply – an Econ 101 recipe for higher prices. What’s a presidential candidate to do about the situation? John McCain and Hillary Clinton both expressed strong support for a repeal in summer gas taxes; Barack Obama chose not to hop on the bandwagon, but offered no immediate alternative. So what can we do in the short term in this regard?

First, eliminate the use of heating oil in American homes. Heating oil and diesel fuel are essentially the same product, so heating oil demand directly impacts the price of diesel and gasoline. Replacing oil heating with gas heating would replace demand for imported oil with demand for natural gas that is produced primarily in the US and Canada.

Eight million homes in the US still use heating oil, and it accounts for roughly 2% of all oil demand in the US. Since oil prices are decided at the margin, a 1% drop in demand could significantly impact price. A $4000 tax credit would convince most heating oil users to switch immediately, and would send a strong signal to gas utilities to expand their service areas. If four million homes switched to gas overnight, this would cost taxpayers $16 Billion in one-time tax credits, about the same as two summers of the McCain/Clinton tax holiday plan. But the additional natural gas demand would be manageable, and the market signal of reduced oil demand would have swift impact.

Second, buy out old gas guzzlers and crush them. Since new vehicles are much more efficient on average, buying old junkers that get less than 20mpg would be an efficient way to reduce oil demand, while potentially helping poorer consumers to find new transportation. For example, offering $2000 per inefficient old car would enable many drivers to retire their old vehicles and move to new, efficient vehicles by using the money as a down payment. 10 million cars could be retired by spending $20 billion, and if each 15mpg vehicle were replaced with a 25mpg vehicle, 210,000 barrels per day of consumption could be eliminated.

Replacing oil heat and getting rid of old gas guzzlers may sound wonkish, but together these ideas could reduce US oil consumption nearly 5%. Unlike many plans under discussions, these steps are feasible and can be implemented today. Of course, these are only steps in a larger energy plan – but it’s better than many of the steps that politicians are currently advocating!


8 million homes * 730 gallons per year / 42 gallons per barrel / 365 days = 381,000 barrels per day

Converting 200,000 bpd of heating to natural gas requires 7 BCF (billion cubic feet) per week of natural gas. Since this consumption is wintertime only, it’s probably closer to 20 bcf per week, which is large, but not unsustainable, given that the US draws roughly 100 BCF per week from storage during the winter.
For cars, if each old 15mpg car is driven 12,000 miles per year, it consumes 800 gallons per year, compared to 480 gallons for the same distance in a 25mpg car. This equates to a savings of 3.2 billion gallons per year, which is equivalent to 210,000 barrels/day.

Can Fuel Efficiency Save Us From Peak Oil?

With gas prices rising daily, Americans are focusing on energy issues of late, and Peak Oil is beginning to enter the common lexicon. Peak oil represents the moment of peak oil production on Earth, after which oil production will plateau and eventually decline. This does not mean that poof – one day the oil is all gone! Rather, it means that oil production growth will slow, and eventually become negative, causing ever higher oil prices until or unless demand also declines.

Many prognosticators now believe that an oil production peak is imminent or has already occurred. While optimists predict production growth for decades to come, and pessimists believe that oil production will soon crash, many forecasts suggest that oil production will soon plateau for a period before beginning to decline. This will indeed be the case if new oil exploration projects just manage to replace declining production in aging fields.

Can the world economy continue to grow if constrained by oil production of 85M barrels per day? The EIA (Energy Information Administration) has estimated that oil demand will grow to 120M barrels per day by 2025, with two-thirds of this total expected to be used for motor transport. These estimates are created using estimates of growth in total vehicle ownership and usage. But what about fuel efficiency? Worldwide vehicle fuel efficiency averages around 20 mpg today; what if this number could be doubled by 2030 using the latest technologies? Doubling worldwide fuel efficiency would reduce demand in 2030 from 120M barrels/day to 80M barrels/day, enabling significant growth in worldwide vehicle usage while keeping oil demand below current consumption! This assumes no fuel efficiency gains in industrial and other oil uses.

Hybrid cars on the market today get in excess of 40 mpg, and new innovations like the Toyota Prius plugin modification (100+ mpg) and the coming VW Golf diesel hybrid (70mpg) push the boundaries much further. Buses, trucks, and other large vehicles are also joining the party, with major shippers like Fedex and UPS acquiring efficient vehicles for their fleets. The lifespan of the average vehicle is 16 years in the US today, so it will take time for high oil prices to cause a worldwide fleet turnover. But the the market signal of high oil prices is unmistakable, with manufacturers like Ford announcing cutbacks in SUV production and a focus on smaller vehicles. And if fuel efficiency can get us from today to 2030, that buys a lot of time for an economic transition to more long-term energy sources.