If you travel the I-10 at all between the San Tan Loop 202 and downtown Phoenix, you might want to plan on heading to Rio Solado College next Tuesday, Feb. 26.

That’s when the Arizona Department of Transportation will be seeking public input on its massive plans to upgrade the highway and explaining what it has cooked up so far.

Similar to some of the open houses that ADOT had in the last few years on the South Mountain Freeway, the session will include opportunities to visit with ADOT planners and engineers on what they’ve cooked up. There also will be a formal presentation at 6 p.m.

The briefing will be 5:30-7:30 p.m. Feb. 26 at the Rio Salado College Conference Center, 2323 W. 14th St., Tempe.

Though ADOT said it still needs to do an environmental study, it still hopes to begin construction in 2021 on improvements proposed for Interstate 10 between the Interstate 17 “Split” interchange and the Loop 202 Santan Freeway across Phoenix, Tempe, Guadalupe and Chandler.

The I-10 Broadway Curve Study includes widening and upgrading 11 miles of I-10 between 24th Street and Ray Road, including the Broadway Curve – which handles more than 40 percent of freeway traffic in the region, resulting in heavy congestion.

ADOT envisions an additional HOV lane in each direction between the Salt River bridges and just west of US 60; a new collector-distributor roadway system that would funnel traffic to local and express lanes to improve traffic flow; reconstruction of the I-10/State Route 143 interchange to improve access to and from Phoenix Sky Harbor International Airport; and improving US 60 near the junction with I-10.

Both ADOT and Federal Highway Administration representatives will be at the briefing on the project, which will be funded through the Maricopa Association of Governments’ Regional Transportation Plan approved by county voters in 2004.

The reconfiguration of the I-10/SR 143 interchange and the I-10/US 60 ramps at the Broadway Curve would separate the ramp traffic from the I-10 mainline traffic, “thereby eliminating the current weaving maneuvers that contribute to severe congestion on the Broadway Curve corridor during peak travel periods,” according to ADOT

The Broadway Curve study is part of a more comprehensive examination ADOT, Mag and the FHA have been conducting for several years along a 31-mile corridor of I-10 and I-17 that’s been nicknamed “The Spine” because “it serves as the backbone for the regional freeway system in the metropolitan Phoenix area.”

For the I-10 portion, the ADOT plan states:

“Growing traffic demand has caused the I-10 corridor between SR 143 and Loop 202 Santan Freeway to become increasingly congested during the morning and evening peak travel periods, and traffic volume projections indicate the congestion will worsen in the future. This study is meant to develop and evaluate near-term freeway improvement options to accommodate the growing traffic demand.”

The complexity of the Spine Corridor is laid out in detail in ADOT’s study, which notes the entire stretch has a total 37 access points, 40 bridges, 26 pump stations and 25 arterial streets that become snarled as a result of traffic jams on I-10 and I-17.

ADOT’s studies say there’s no time to be lost on the improvements because the future looks grim.

“Existing daily traffic volumes ranges from 100,000 to 250,000 vehicles per day,” it states. “By 2040, the horizon year for the Corridor Master Plan, traffic volumes will grow to 150,000 to 300,000 vehicles per day.”

Planners say that what many motorists probably know already: “In most cases, travel times along the corridor are often double or triple the travel time as compared with making the trip without congestion.”

Already the traffic crawls are creating a phenomenon called “peak spreading,” which basically means rush hours get longer.

If nothing is done, the study warns, by 2040, “congestion will spread to other times of the day, and in some portions of the corridor will extend to more than 12 hours.

The 2018 study estimates it will cost at least $2.5 billion to cover all the improvements it recommends along the entire 31 miles of the Spine Corridor.

But that amount leaves several dozen other recommended projects on the table without funding.

Other improvements that were recommended but so far have not been funded include: upgrading the I-10/Chandler Boulevard interchange for bicyclists and pedestrians; improving the Warner Road/I-10 interchange; and upgrading the I-10/Baseline Road intersection – which Tempe officials say is the most dangerous intersection in the city in terms of the number of crashes that regularly occur there.

While tens of thousands of motorists use the Spine Corridor and will be affected by ADOT’s plans, only 496 people responded to a survey that ADOT conducted in early 2017.

Part of the study is available at azdot.gov/I10BroadwayCurve. ADOT also is soliciting public comment on the plans that will be discussed Tuesday at Rio Salado College. Comments must be submitted by April 1 to projects@azdot.gov.

(3) comments


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This project is really quite disappointing, it looks like it's been value-engineered to death. While it does eliminate the weave conflict between SB 143 and EB 10, that ramp remains in its current configuration now instead of the long-proposed, high-speed directional flyover. You're still going to have the signal at 48th St and 143 is still going to queue significantly, even with a turn lane.

It also appears that ADOT has spent considerable resources on acquiring ROW for the prior plan, only to now not need all of that land they've already cleared. At least that's the way it looks on the plans they have posted. I'm not a fan of a lot of the new geometry.

I guess we have to trust ADOT. I know they have been trying to value engineer everything to the extreme the last several years and I hope this doesn't come back to bite us.

And does this or does it not include reconfiguration of the Baseline interchange? I guess I'll have to find out at the open house...


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