Sometimes it feels silly to use your turn signal when there are a few cars or even no one around on the road. Or maybe you just don’t feel like signalling. Turns out that may be illegal, according to a recent state Supreme Court ruling.

A previous Court of Appeals decision held that drivers only must signal when it impacts public safety, and so the Supreme Court sought to determine whether the phrase “when required” in original law compels drivers to use their signal every time they turn or change lanes.

“We hold that it does,” the decision reads. “The plain language of RCW 46.61.305 requires drivers to ensure turns and lane changes are done safely and with an appropriate turn signal.”

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The ruling is based on the case of David Brown, who in 2015 was driving in Kennewick, Washington, where state patrol officers observed him initially signal when entering a turn lane, and then stop at a red light and not reactivate his left turn signal at the light or while executing the left turn. Officers pulled him over, and then arrested him after a breath test showed a 0.26 breath alcohol content.

The state argued in court that it had cause to pull Brown over for failing to continuously signal his intent to turn left, and Brown argued that the breath test evidence could not be used because the traffic stop had no cause. The court concluded that a driver is not required to reactivate a turn signal when entering a turn-only lane, and so officers had no cause to pull Brown over. The Court of Appeals later concluded that a signal is only required when public safety is affected.

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In the conclusion, the state writes:

“The plain language of RCW 46.61.305 requires a driver to signal his or her intent to turn or change lanes on a roadway. The phrase “when required” relates to the manner in which that signal is made. Brown did not continuously signal his intent to turn left; therefore he violated ROW 46.61.305. This is the only issue before the court.Accordingly, we reverse the Court of Appeals and remand the case for further proceedings consistent with this opinion.”