Aren't roundabouts better than traffic lights from a fuel standpoint?
Not that you can't have a proper traffic jam at a roundabout, either...
EDIT: Got un-lazy for a few seconds and did some "research". According to Nevada DOT:
"Many vehicles must wait for the light to turn green in a signalized intersection. While stopped, the vehicle’s exhaust emits more undesirable pollutants and gases into the atmosphere. Because roundabouts often eliminate such stops and improve traffic flow, they also reduce vehicle emissions and fuel consumption. In one study, replacing traffic signals and signs with roundabouts reduced carbon monoxide emissions by 32 percent, nitrous oxide emissions by 34 percent, carbon dioxide emissions by 37 percent and hydrocarbon emissions by 42 percent.
Gasoline use is also reduced as traffic moves more efficiently through roundabouts, without the start and stop found at traditional intersections. Studies have shown that fuel savings can be up to 30 percent in roundabouts. At 10 intersections studied in Virginia, this savings amounted to more than 200,000 gallons of fuel per year.
Without the stop and start of traditional traffic intersections, roundabouts can also reduce vehicle noise pollution."