’22 in review: Diverging-diamond interchange pitched for I-10/SR 347

ADOT is considering a diverging-diamond interchange at Interstate 10/State Route 347.

For residents commuting to and from the Valley during rush hour, improvements to the interchange at State Route 347 and Interstate 10 can’t come soon enough.

According to Arizona Department of Transportation figures from 2018, the stretch of SR 347 from Maricopa Road to I-10 saw average annual daily traffic of more than 38,000 vehicles. That number is projected to nearly double by 2040.

In September, ADOT proposed a design in use in France since the 1970s, the “diverging-diamond interchange,” to move traffic through the congested junction. The interchange would carry traffic through the area more smoothly and more safely, with fewer and less serious crashes, according to ADOT. It would also cost less to construct.

According to ADOT, most of the improvements to the interchange would be concentrated on the SR 347/Queen Creek Road alignment, which would be split in two — one alignment for each direction of traffic. The horizontal alignments for the ramps would be shifted farther outward to tie into the new configuration. The vertical alignment for eastbound traffic would match the existing road as closely as possible over the existing bridge to allow for its continued use.

The new configuration would have four eastbound lanes across the existing bridge and three westbound lanes across a new bridge as well as 10-foot shoulders across both bridges. A 5-foot bike lane in both directions would be included.

The new bridge and nearly half of the new interchange would be built in a way that minimizes traffic disruptions. Some short-term lane closures and detours would be necessary, including on I-10 for the new bridge construction. That would likely be done by rerouting I-10 traffic through the existing interchange ramp terminals.

The current interchange was built in the late 1960s and reconstructed in 1992. The basic urban diamond configuration remained, though additional traffic capacity was added because the interchange had become the new primary I-10 access point for SR 347.

The final environmental assessment and design concept report are expected to be complete and available early this year.