Round and Round: Rebuilding the Dowling Road and Seward Highway interchange.

• Author: Newman, Amy
• Position: CONSTRUCTION

One of Anchorage's largest construction projects in 2022 was the Alaska Department of Transportation and Public Facilities' (DOTEtPF) $43 million reconstruction of the Dowling Road/Seward Highway interchange. Work on the federally funded, multi-phase project will replace and expand the Dowling Road roundabout and the Seward Highway overpass, both of which are nearing the end of their useful life. Construction on the interchange began in May and is expected to be completed in 2023.

Work on the interchange is also the culmination of a decades-long project designed to increase safety and improve the flow of traffic along the Seward Highway from 36th Avenue to Rabbit Creek Road. Traffic along the highway has outpaced growth projections made in the early 2000s.

"This is as much about connecting the mainlines [as] it is about replacing the roundabouts, which were constructed in the early 2000s, and taking the opportunity to improve them for the next twenty to thirty years," says engineer Joseph Taylor with Lounsbury & Associates, which served as the project's prime consultant.

The DOT&PF put the project out to bid with a two-year construction timeline, says DOT&PF project manager Jacob Gondek. However, a collaboration with general contractor Quality Asphalt Paving (QAP) led to a different approach to the project's logistics, one Gondek says helped decrease traffic delays and interruptions and created greater consistency and predictability for travelers. The collaborative approach also put the project ahead of schedule, with all major work expected to be completed in October.

"I think the key is to recognize that the highway will be back up before winter," Gondek says. "We will still have work left to do in 2023. but it will be drastically less impact to the traveling public under this new partnering approach."

All About the Roundabout

The Dowling Road crossing under New Seward Highway was the first multi-lane roundabout in Alaska. When it opened in 2004, it replaced a signalized lighting system that controlled traffic at the highway ramps. The roundabout, with two lobes on either side of a section underneath the highway, was designed to improve the flow of traffic and decrease backups on the off-ramps by redistributing traffic along Dowling.

"We were experiencing queuing on the ramps. Vehicles were stacking up on the peak hours, and they were backing up the ramps and spilling out onto the highway," Taylor explains. "That's a dangerous situation when you have 70-mile-per-hour free-flow traffic."

The original roundabout had an inscribed circle diameter (ICD)--the...