By holding planes at their gates, fuel use declined but efficiency did not

April 4, 2011
Hold planes at gate, cut greenhouse gas

All that’s needed to reduce greenhouse gas emissions relating to air travel is a little patience.

That’s according to a study looking at how best to get airplanes through busy airports. “There is going to be a significant decrease in greenhouse gases from this,” says Hamsa Balakrishnan at the Massachusetts Institute of Technology, who led the study.

Researchers found that by holding planes at their gates for an average of 4 minutes and 18 seconds, congestion on busy runways at Boston Logan International Airport diminished. This allowed planes to depart more efficiently: Taxiing time dropped by 20 percent — balancing out the extra time at the gate — and fuel use decreased by nearly 20 gallons per plane. The study has been published as an MIT Technical Report and was funded by the Federal Aviation Administration. Balakrishnan intends to submit it to a peer-reviewed journal.

Domestic flights in the United States emit about 6 million tons of carbon dioxide from taxiing per year, Balakrishnan says. Similar emissions occur in Europe, where planes spend an estimated 10 to 30 percent of their journey time taxiing on runways.

A number of airports have already achieved fuel savings by optimizing flight paths for planes on arrival. Combining the two strategies could reduce emissions by millions of tons per year, Balakrishnan says.


A study found that fuel consumption was lower when planes stayed at their gates than when they queued up for takeoff. (EYESWIDEOPEN/GETTY IMAGES)

New Scientist

Should electric cars pay substitute gas tax?

Oregon lawmakers are considering charging the owners of electric vehicles for every mile they drive, to replace the gas-tax payments they won’t be making.

The bill, in the state’s House of Representatives, would charge drivers of electric and plug-in hybrid vehicles up to 1.43 cents for each mile they drive, beginning with cars from the 2014 model year.

The Oregon Department of Transportation would be responsible for finding a way for vehicles to electronically report the distance they’ve traveled, and drivers could receive refunds for miles driven outside Oregon.

“It’s a fairness issue,” said state Sen. Bruce Starr, a proponent of the bill. “They’re not paying any gas tax. Everyone else is paying; why should they get a fair ride?”

Opponents say it’s too early to tax electric-vehicle use because the state should be doing everything it can to make non-polluting vehicles attractive to buyers.

It may be unfair, “but the point is, we’re trying to increase the number of non-polluting vehicles on the road,” said John Christian, chair of the Oregon Electric Vehicle Association. Christian said he agrees that electric-vehicle owners should pay road-use fees, but he would prefer that the tax not kick in until 25 to 50 percent of vehicles are non-polluting.

Oregon has relied on gas taxes for road maintenance since 1919, when it was the first state to create a fuel levy. The tax is now 30 cents per gallon, which is projected to pump $1.1 billion into the state highway fund over the next two years to pay for road construction and maintenance.

Oregon officials have been concerned about the potential for dwindling gas-tax revenue since fuel-efficient hybrid vehicles were introduced a decade ago. They experimented with a pilot project that included GPS devices that tracked and reported the number of miles driven inside Oregon. The GPS approach was ruled out amid privacy concerns, but officials say it could still be an option for drivers who prefer it.

Lawmakers in Washington state are considering a proposal to charge electric-vehicle owners a flat fee of $100 per year. Proponents of Oregon’s approach say their plan is more fair because people who drive more pay more, which is the way gas taxes work.

— Associated Press

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