Air Travel vs. RAV4 Hybrid Carbon Footprint

When I flew out in October 2005 to pickup our 2003 Prius, , I used the flight crew provided passenger count and fuel burn and came up with +60 MPG per occupied passenger seat. The dealer picked me up so I didn't include their fuel burn. To be precise, we should include fuel for both round-trips at the airports.

Bob Wilson

 

For fuel efficiencies per passenger seat of very many commercial aircraft, starting with the class used for your JFK-SFO reference, see here:

https://en.wikipedia.org/wiki/Fuel_economy_in_aircraft#Medium-haul_flights

I'm not seeing any pattern of smaller jets being better. The latest 787s can pull over 100 mpg/seat over extremely long hauls. The keys are to pick the right aircraft for the distance, and not fly a lot of empty seats.

The commuter jets have fairly uniformly poor efficiencies, probably related to the high fuel cost of climbing up to speed and altitude being amortized over just a short distance. The commuter turboprops have a significant advantage over the jets for these short hops.

Keep in mind also that your RAV4 can't take an equally direct route as the aircraft. It may be only 2580 air miles from JFK to SFO, but it is 2940 highway miles, a 14% road distance penalty. Your RAV4 will need 73.5 gallons, not 65.

 

I fly a lot for work.

Long haul doesn't automatically mean efficient. The most recent flight I took was about 9,650 miles and burnt about 38,220 gallons of fuel to move about 160 passengers.

That makes just over 40 seat-miles per gallon, which is on the low side compared to most flights I take. Fuel efficiency was sacrificed for trip time, to avoid a refueling stop.

One of the more efficient flights I regularly take is about 2,450 miles using 5,000 gallons of fuel for ~185 passengers, which makes for about 90 seat-miles per gallon.

Obviously the numbers are only that good when the planes are full, but guess what? most of the flights I've been on in the past 6 months were packed.

Commercial aircraft last about 30 years before they are scrapped/recycled. That's considerably longer than most cars. Just another thing to bake into the math.

Here's another angle: Concrete pavement requires a lot of energy to produce. 1000 miles of highway involves a lot more concrete than two runways 1000 miles apart.

 

While this is a good point, how many passengers use the highway vs the runways? Per passenger, the highways may not look as bad.

 

That amounted to 1600 pounds of fuel per passenger. I.e. a lot more fuel than payload. It takes a lot of fuel to carry all that fuel.

That wikipedia page linked above shows an example of fuel economy vs distance:


Flight distance

For long-haul flights, the airplane needs to carry additional fuel, leading to higher fuel consumption. Above a certain distance it becomes more fuel-efficient to make a halfway stop to refuel, despite the energy losses in descent and climb. For example, a Boeing 777-300 reaches that point at 3,000 nautical miles (5,600 km). It is more fuel-efficient to make a non-stop flight at less than this distance and to make a stop when covering a greater total distance.

Note also that cars spend an overwhelmingly majority of their life, just parked. Commercial airliners spend significantly less of their life parked, a lot more of it actually operating.

Where I travel, most highways are not concrete. Though I haven't looked up any lifecycle carbon difference for concrete vs asphalt.

 

I'm linking the attention paid to quantitative side of environmental science here. Y'all must be Prius drivers or something.

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A country without a roadway network seems incompatible with large populations, relatively prosperous ( a term that gets used here a lot )

I'm confident that concrete roadways are more durable under heavy use than asphalt. Poor roadbed construction can kill all though.

Airport runways are vastly better designed and constructed compared to roadways. Interesting topic.

 

Speaking as an Alaskan-in-exile, I can mostly confirm that though there are some interesting surprises here and there.

 

Without extensive road networks, undisturbed forests can persist and fewer landslides will happen in steep places. But economies would extract less money. It's a +/- being worked out by groups not represented here.

 

I've generally noticed better foul-weather traction on asphalt. Though it varies by surface texture, which appears to be a somewhat controllable property.

They must be. Even a light 737 weighs as much as the heaviest interstate trucks not needing special permits, 80,000 to 120,000 pounds. And those trucks are only bouncing a few inches from potholes, not falling out of the sky with a big hard bounce on landing.

Roadbed damage varies with about the 4th power of axle load. Those jumbos are far heavier than any trucks, and tend to have fewer 'axles'. I'm seeing specs for a 747-8 with a max takeoff weight of 987,000 pounds, and max landing weight (think hard touchdowns) of 757,000 pounds. And an A380 taking off at 1,234,600 pounds, landing at 850,984 pounds.