The DOT offset the $1 million project with more than $600,000 in rebates from National Grid as part of the company’s Energy Initiative Incentive Program. Given the expected savings in electricity costs, RIDOT Director James R. Capaldi said in a statement today the signal changes were done at “essentially a break-even cost while saving energy and reducing maintenance costs.”

LEDs look like tiny light bulbs, but unlike conventional incandescent bulbs, they don't have a filament that will burn out. Instead, they are illuminated by the movement of electrons in a semiconductor material.

The old traffic lights had one incandescent bulb behind each red, green and yellow lens. The new ones have up to 122 LEDs spread across the light. The result is a more even, more intense light.

The LED lamps require just 14 watts of energy compared with 116 watts per lamp for an incandescent bulb.

The DOT says the savings at one intersection with eight signal heads can be dramatic – with an annual electric bill of just $99 for the LED lamps compared with a bill of $810 with the old incandescent bulbs. Also, LEDs last five to 10 years, compared with about one year for the old bulbs.