Know the Road with the CHP: When do speed limits take effect?

FRESNO, Calif. (KFSN) -- An ABC30 viewer wanted to know: When is it best for me to change speed limits? Would it be before or after the posted sign, or is it when it's visible to my eyes?

"We always recommend as you're traveling down the highway to maintain a high visual horizon," said Sgt. Brian Pennings with the California Highway Patrol. "That way you can perceive and predict what's going to happen in front of you, such as a speed limit change."

"If you see a sign in front of you that indicates an increase or decrease in the speed limit, you should have enough time to perceive and react to that change of speed," he explained.

"So when exactly is it enforceable? The technical answer is: the speed limit changes at the prolongation of the signpost," Pennings said. "In other words, an imaginary line that travels across the roadway where the sign is posted next to it."

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