I-5 - 179th St. Interchange - Interchange Improvements

Needs & benefits

Originally built in the early 1960's, the existing I-5 Northeast 179th Street interchange is in need of upgrades and improvements to bring it up to today's design and safety standards. As growth and development in Clark County continues, it's crucial to upgrade our infrastructure to ensure we're meeting the demands of increased traffic today, and into the future.

In partnership with Clark County, studies were conducted on various interchange concepts, including signalized intersections, a diverging diamond interchange, and a single-point interchange concept, to find the best solution for accommodating future growth and event traffic.

Following public engagement to gather input on interchange types, roundabouts along this interchange were chosen for their effectiveness in improving traffic flow and safety. Studies have shown that roundabouts reduce congestion and delays, have fewer conflict points, promote traffic calming, require less maintenance compared to other intersection types, and improve overall traffic efficiency.

Additionally, while roundabouts are designed to accommodate various vehicle types, including large freight trucks, truck-friendly design elements such as a "truck apron" can be included in the roundabout designs to accommodate large vehicles. Truck aprons are a raised section of concrete around the center island of the roundabout, which acts as an extra lane for large vehicles to complete turns.

While roundabouts are increasingly used in Southwest Washington for safety and efficiency, their suitability for each intersection is carefully evaluated based on factors like accident history, traffic volume, vehicle types, bicycle and pedestrian needs, and cost. Engineers consider these factors to determine the best solution for each intersection.