Broadway Curve Improvement Project

This chart illustrates the components of the I-10 Broadway Curve Improvement Project, a four-year effort to improve safety and efficiency for tens of thousands of Valley motorists.

Starting this week, billboards, social media and television and print media will carry messages urging thousands of motorists to prepare for four years of disruptions in their driving routines.

It’s not exactly Armageddon that the Arizona Department of Transportation will be heralding.

But it won’t be a walk in the park for car and truck traffic on I-10 and motorists going to and from Sky Harbor International Airport. 

And even if you don’t use I-10, you can expect significant increases in traffic along freeways in the East Valley and major arterials as motorists try to evade the inevitable tie-ups that will be caused by the I-10 Broadway Curve Improvement Project.

“There’s no way to sugarcoat it,” said ADOT spokeswoman Kim Noetzel. “It’s going to be impactful.”

Seven years in the planning, the work is ready to begin as crews next week start scraping the asphalt along 11 miles of Interstate 10 between the junction of the San Tan and South Mountain freeways and I-17 near Phoenix Sky Harbor International Airport. This weekend, some I-10 ramps were closed through 4 a.m. Monday for preliminary work. 

The project also will involve work about a mile of east- and westbound US 60 between I-10 and Hardy Drive and a one mile of north- and southbound State Route 143 between I-10 and the southern end of the SR 143 bridge over the Salt River. 

Motorists’ pain will only increase as the work picks up steam on a project aimed at preventing virtually round-the-clock rush hour gridlock on I-10 in the heart of Maricopa County.

“When the first phase of construction begins this summer,” ADOT spokeswoman Alexandra Albert said in a virtual briefing last week for Tempe residents, “drivers should prepare for weekend closures on I-10 and US 60.”

ADOT already wants commuters to prepare by studying and then taking different routes –especially if they work in downtown Phoenix. 

The highway agency is going to unprecedented lengths to help them do that.

“We very much want to do everything that we can so that motorists, visitors, businesses can plan in advance to lessen the impacts,” Noetzel said. “We’re doing things with this project that we’ve never done before.”

In a recent virtual briefing for Tempe residents, ADOT representative Alexandra Albert put it another way:

“ADOT is doing some really significantly different things than they have in the past and it’s because of the size and the scope and the location of this project.”

For the first time, ADOT has developed a project-specific mobile app. It has prepared an advertising blitz on TV, radio and in newspapers. It’s ordered up billboards and even putting warnings and reminders on gas pumps. It has created a home page for the project at where people can stay up to date and get the mobile app.

ADOT representatives have been briefing dozens of chambers of commerce and other economic development organizations from Glendale to Gilbert, holding town halls and planning to open a field office for the general public in Phoenix where anyone will be able to drop by Monday through Fridays just to chat about the work. 

It also has scheduled has scheduled a virtual open house on the project 5:30-7 p.m. Aug. 4 at

All this, Noetzel explained, is being done “to create that awareness and make sure that people know where to get resources.”

Indeed, ADOT has spent two years talking with people about the project, she said, because “one of the underlying tenets of our communications approach in this is no surprises.”


A first and significant scope

ADOT calls the Broadway Curve project “the first major urban freeway reconstruction project in Maricopa County.”

Its major components include:

• Widening I-10 to six general purpose lanes and two high-occupancy-vehicle, or HOV, lanes in each direction between US 60 and I-17 and adding a fourth general purpose lane in each direction between Ray Road and US 60.

• Adding collector-distributor roads that parallel I-10 between Baseline Road and 40th Street to separate through-traffic on I-10 from local traffic entering or exiting the highway. Unlike frontage roads along portions of the existing freeway system, these CD roads will not intersect with perpendicular roads.

• Rebuilding the I-10 interchange with SR 143 to improve traffic flow and create direct connections to and from SR 143 for drivers in the I-10 HOV lanes. This part of the project will reduce lane changes and often hair-raising weaving between Interstate 10 in the Broadway Curve and the entire SR 143 and I-10 interchange will be replaced by ramps that make a direct connection for drivers from the general and HOV lanes and eliminates the existing cloverleaf ramp that connects southbound SR 143 with eastbound I-10.

• Razing and replacing the Broadway Road bridge over I-10 as well as replacing the 48th Street bridges over I-10 and widening the I-10 bridges over the Salt River;

• Building two bridges for pedestrians and bicyclists over I-10, erecting seven sound and retention walls and installing a wrong-way driver detection system including thermal cameras, flashing signs and other specialized equipment that ties into ADOT’s intelligent transportation system. 

Of the project’s total $776.6 million cost – less than half the cost of the South Mountain Freeway – $676.6 million will be spent on construction, with $615.6 million going to the developer, a joint venture of Pulice Construction, FNF Construction and Flatiron Constructors that goes under the name of Broadway Curve Constructors. 

The remainder of the project’s total cost covers the intelligent transportation system signal upgrades, right-of-way acquisition and paid advertising aimed at motorists. 

As a “design-build” project, contractors are “encouraged to use innovation and develop alternative concepts to reduce project time and impacts to the traveling public and community while construction is underway,” ADOT notes.


Better now than later

The Broadway Curve project covers roughly a third of the 31-mile I-10-/I-17 corridor that the Maricopa Association of Governments – the Valley’s major highway planning group – and ADOT call “The Spine” because it handles 40 percent of all Valley traffic daily.

The Spine comprises 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.

Combined daily east and westbound traffic already comes close to 300,000 vehicles through the Broadway Curve daily, and that number is expected to increase as the Valley’s population steadily grows.

ADOT Director John Halikowski at one point noted, “Interstate 10 is a key commerce corridor that supports Arizona’s efforts to succeed in the global trade market and a vital transportation route for millions of people who live in, work in and visit our state every year. Improving safety and reducing congestion will truly benefit everyone who relies on our highway system, as well as thousands of businesses along the I-10 corridor. We are proud to deliver a project that will improve quality of life for so many people throughout the region.”

Though the pandemic significantly reduced traffic volume, no one expects that to remain the case.

Traffic crawls are creating a phenomenon called “peak spreading,” which basically means rush hours get longer. If nothing is done, one ADOT 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 estimated it would cost at least $2.5 billion to cover all the improvements it recommends along the entire 31 miles of the Spine Corridor.

If nothing was done with the Broadway Curve, ADOT’s environmental impact study notes, it “would result in increased traffic congestion in the area as growth and development continue.”

“The level of congestion is anticipated to be more severe in various segments of the corridor, if no improvements were implemented and there is a need for improvements to maintain the functionality and mobility in this corridor,” it adds, warning:

“By year 2040, the traffic operations along the I-10 and interchanges in the study area would further degrade with the growth indicators forecasted for the foreseeable future. Without major improvements, the I-10 in the study area (the area covered by the Broadway Curve project) would suffer degraded traffic conditions, travel delays, and challenging mobility for moving goods, services, and people through the study area.”


The gain after pain

After the project’s pain comes what ADOT sees as a gain – not just for the 1,200 construction jobs it will create but also for the future of more than 4,600 businesses, that include 50 of the region’s largest employers.

Noting that I-10 “is part of a key commerce corridor that connects ports in California with markets in Texas and beyond,” ADOT’s environmental study  states, “The improvements will make I-10 a more favorable route for commercial truckers whose travels through the region support our local businesses.”

ADOT envisions the project will accommodate current and planned system linkages for bus services using I-10, facilitating more ridesharing and rapid transit use.

It also promises to make driving safer by reducing lane changes. 

Then there is the project’s overall impact on traffic, which ADOT describes thusly: “With the addition of new travel lanes, HOV lanes and the CD roads, capacity on I-10 will increase by 60 percent. This will better accommodate existing traffic and increased traffic as the region continues to grow.

“Adding capacity to I-10 will reduce congestion and travel times. Greater efficiency means drivers can get to and from the places they need to be in less time. According to an economic evaluation conducted by MAG in 2020, the improvements will save motorists 2.5 million hours annually otherwise spent in traffic – totaling $130 million a year in time savings. These savings are due to quicker commutes made possible by the improvements vs. slower travel times without them.”

 For motorists whose stomach knots in traffic, the study puts it another way:

“The current average speed on eastbound I-10 between I-17 and US 60 during afternoon rush hour is 32 mph. The average speed is projected to increase to 40 mph by 2025 with the improvements. Without improvements that speed limit is projected to decrease to 29 mph by 2025.”


But first, the pain

The environmental study says that while motorists can expect “temporary delays and slower speeds,” access to businesses and neighborhoods in the area “would be maintained at all times. 

“Traffic delays and slower speeds would be experienced equally by everyone who lives or passes through the study area,” it says.

“Traffic operations would remain challenged, and congestion would become more prominent, particularly in the peak periods,” the environmental study anticipates.

ADOT anticipates the I-10 will be shut down in both directions in the project area at least 50 times over the next four years. Most of these closures will occur on weekends though some also will occur during the work week.

The detours, closures and lane restrictions the project will generate explain why ADOT hopes even occasional users of the freeways and byways impacted by the project will download the mobile app and pay attention to the other channels of communication it is deploying for the duration of the work.

That’s especially true for people driving to or from Sky Harbor.

Noetzel said ADOT and its construction partners have been talking with airport officials for more than year – and not just about the impending impact of the project itself. “We need to start talking now about educational campaigns on getting people to the airport once construction is complete,” she said, adding, “Our first goal is to get them to the airport while construction is going on.”