Domestic flights in the US emit about 6 million tonnes of CO2 from taxiing per year, Balakrishnan says. Similar emissions occur in Europe, where planes spend an estimated 10 to 30 per cent of their journey time taxiing on runways.
Six billion tonnes of CO2--not to mention other pollutants--from taxiing, plus upwards of 30% of total vehicle travel time just waiting on the runway. This is as bad as cruising for curb parking.
If taxiing can be reduced it may make plane travel more pleasant, as well. I haven't seen studies that estimate the disutility of waiting on a runway, but I suspect that waiting in the queue for an indeterminate amount of time is probably valued differently than time at the gate or in the air. In any event reducing taxiing seems like a good idea.