If you're turning left on a state road, the traffic light may soon have a new color

Red means stop and green means go. Well, except at intersections with traffic signals that show solid a green light in the left-hand turn lane. In that case, green means yield, and proceed with caution.

Confusion arising from that discrepancy is why drivers may be seeing new traffic signals in left-hand turn lanes on state roads. The Massachusetts Department of Transportation has worked for the past several years to change those solid green signals to yellow arrows.

“As a driver, when you see green, you think, ‘go,’” said Neil Boudreau, MassDOT's assistant administrator for traffic and safety. “People would misconstrue green as ‘go,’ even though when you’re seeing a (solid) green left-turn signal, you’re supposed to wait to make sure there is no oncoming traffic before turning. Drivers, most drivers, see yellow and they know they have to slow and assess the situation.”

The program for the yellow arrow left-hand traffic signal began in 2013 with an installation in Lenox. The state had to get permission from the federal government due to make the change.

A second one was installed in Littleton in 2014.

Since then, the state has been changing all previous traffic signals. Now, if any light is replaced, the new version will be installed. The change affects only intersections that already have solid green lights in the left-hand lane, Boudreau said.

The effect has been a positive, Boudreau said.

“All of the data — and we’ve done all of the research — points to a reduction in crashes,” Boudreau said.

Although the MassDOT only installs them on state roads, Boudreau said many communities take advantage of grants to install the newer traffic signals when making replacements.

“Over time, you’ll start seeing them more and more at local intersections,” he said.

Norman Miller can be reached at 508-626-3823 or nmiller@wickedlocal.com. For up-to-date public safety news, follow Norman Miller on Twitter @Norman_MillerMW or on Facebook at facebook.com/NormanMillerCrime.

This article originally appeared on MetroWest Daily News: Solid green left traffic signals replaced in MA by yellow arrows