9/17/2015
Idaho 75 speed-limit increase south of Ketchum begins next week
KETCHUM – Following an engineering-traffic study of Idaho 75, thousands of drivers will see an increase next week in the speed limit for approximately 1.5 miles of roadway. The speed limit will rise 10 mph from near Cold Springs Drive to the Big Wood River Bridge.
On Tuesday, work will take place to extend the 55 mph speed zone north to about milepost 125.6 near Owl Rock Road. The speed limit also will increase to 45 mph through the Hospital Drive intersection to near the Big Wood River Bridge. The speed limit will remain 35 mph from the south side of the bridge north into Ketchum.
The average daily traffic for the section of road varies from 8,000
to 13,000 vehicles per day, with volumes peaking in the summer.
The engineering-traffic study was conducted throughout the spring and summer months following reconstruction of this section of roadway, which was completed in October 2014. The project improved roadway safety with addition of wider shoulders, center- and right-turn bays, and improved access to businesses and residential communities.
In accordance with federal guidelines, ITD uses the 85th percentile speed of free-flowing traffic for determining a safe and reasonable speed for a given road section. Traffic engineers set the limit at a speed at which 85 percent of the traffic is driving. This reflects the safe speed as determined by a large majority of drivers, and encourages better traffic flow by reducing variances in speed.
These limits are also imposed to assist Idaho law enforcement. Speed limits that reflect the behavior of the majority of motorists are found to be successful. The engineering-study results and recommendations were reviewed by Blaine County law enforcement and local leaders prior to approval.
Drivers are reminded that the current speed limit remains in effect until the new signs have been installed.