In consultation with local jurisdictions, the Idaho Transportation Department this week authorized increasing the speed limit by 5 mph to 50 mph. A maintenance crew will replace existing signs on Thursday between mileposts 361 and 363. The new speed zone is near the Idaho 6 junction, about a mile from Potlatch.
The decision to increase the speed limit by 5 mph came after a December engineering study that indicated at least 85% of the motorists on that segment already drive at 50 mph. Increasing the speed limit will improve highway safety by ensuring that more drivers travel at the same speed.
Vehicle crashes are least likely to occur when vehicles travel at or slightly above the 85th percentile, ITD engineers explain. The 85th percentile speed reflects a safe speed for existing conditions as perceived by most of the motorists and becomes “largely self-enforcing.”