The detrimental impact of traffic lights on the environment should be considered when deciding between traffic lights or roundabouts. The San Diego County Environmental Impact Report does not adequately address the issue.
While the carbon footprint of traffic lights is significant, the carbon footprint of roundabouts is close to zero. Roundabouts significantly improve air quality over traffic lights, and require no installation, powering, or maintenance of signal equipment or overhead lights, making them more cost effective over the long term.
According to the Federal Highway Administration (FHA), roundabouts significantly decrease fuel consumption and emissions by as much as 30%. The FHA states that roundabouts provide environmental benefits by reducing the number of acceleration/deceleration cycles and the time spent idling compared with traffic signals. Even when there are heavy volumes, vehicles continue to advance slowly in moving queues, rather than coming to a complete stop.
For example, according to San Diego County, each roundabout on La Jolla Blvd is estimated to save 20,000 gallons of gasoline annually, avoiding 9.9 lbs. of particulate pollution. The County also claims that installing 320 roundabouts in San Diego could reduce CO2 emissions by 60,480 metric tons annually — equal to the annual emissions of 10,900 cars. The Environmental Protection Agency backs this claim up by stating just one roundabout can eliminate 189 metric tons of CO2 emissions annually, equivalent to 37 cars.
Kansas State University studied three different locations that were converted from four-way signal control intersections to modern roundabouts. The study found a 38-45% percent decrease in Carbon Monoxide emissions, a 55-61% percent decrease in Carbon Dioxide emissions, a 44-51% percent decrease in Nitrogen Oxides, and a 62-68% percent decrease in Hydrocarbons.
It should be no surprise to hear that roundabouts qualify for The California Environmental Quality Act (CEQA), and are eligible for Federal funds from the National Environmental Policy Act (NEPA). Obviously, traffic lights do not qualify.
In addition, roundabouts are more efficient than traffic lights, because they move traffic at a steady pace, moving traffic through 20% more quickly and efficiently. Roundabouts eliminate waiting at red lights and give immediate access to roadways. Roundabouts are in compliance with our dark sky mandate, are much more beautiful, and are up to nine times safer than traffic lights. Roundabouts will help maintain the Covenant’s rural character.