SH-55 Eagle Road Safety Corridor

Our ongoing commitment is to enhance safety on Idaho’s highways. At the request of the city of Meridian, we conducted a thorough traffic operational study of Eagle Road. This involved working group meetings with local cities and law enforcement. We also contracted with a national traffic engineering expert consultant for review of signal timing and traffic operations. Additionally, ITD works to stay abreast of new and evolving technology by interacting with trade associates and nationwide research, and variable speed limits have been discussed in these national meetings. The idea for the variable speed limit pilot on the State Highway 55 corridor was put forth by ITD staff members similar to what has been used in Idaho construction zones on Interstate 84 and Interstate 90. It is a means of trying to inform drivers what speed limit would be appropriate during both congested and non-congested periods.

ITD worked with local stakeholders, community leadership and law enforcement to determine the best times for reduced speeds. Based on these conversations and the available data, the speeds will be reduced to 45 mph from 7 to 9 a.m. and from 4 to 6 p.m. Once in place, the corridor will be continually monitored to ensure the limits remain effective.

ITD began by increasing safety signage in the corridor and closing some of the unsignalized left turns. Additionally, the department installed a variable speed limit system. The VSL system includes signs with LED number panels, flashing beacons, and speed feedback signs to encourage caution during heavy traffic volumes on Eagle Road. At non-peak times, the signs will remotely return the speed limit to the existing posted speed in the pilot area.

The pilot project area is from SH-44 to I-84 with VSLs from Franklin Road to Chinden Boulevard. Variable speed limit signs are installed at an interval of at least every mile along the roadway and during predetermined congested traffic times display a 45-mph speed limit.

Over the next month, ITD will activate variable speed limit signs. These LED panels display the current speed limit, and flashing beacons activate when lower speeds are in effect so drivers know when to slow down. Additionally, speed feedback signs show how fast vehicles are moving to encourage compliance.

To the department’s knowledge, this would be the first VSL corridor on a six mile long signalized urban highway corridor in the United States. The practice has been used on freeways in states like Arizona, Colorado, North Dakota, Oregon, Tennessee, and Virginia. FHWA has reviewed these installations and found significant safety benefits as outlined in Circular FHWA-SA-21-054.  ITD has deployed the practice in temporary construction work zones on Interstate 84 (I-84) in Canyon County and the Magic Valley. The study will span two years, after which ITD will assess the data to determine the next steps for this corridor.  

Additional safety signage, removing un-signalized left-turn access, and introducing a variable speed limit zone with speed feedback signs assisting only during peak congestion times. The corridor is over six miles long with 18 signals and 60,000 vehicles per day. Through this proposed two-year pilot effort, our goal is to enhance safety by implementing these several key measures that should work together to reduce crashes