Widening I-10 Through Tucson

By Terry Ertter | September 28, 2010

Anyone living in a large or medium Western city has had to learn to live with delays and detours caused by constant road improvements. Highways and surface roads need more lanes to handle increased traffic. Older roads must be rebuilt to carry heavier loads.

Even by Western standards, though, the current $200-million Interstate 10 widening project in Tucson promised to be one of the great urban highway disruptions of our time. It's the most expensive single highway project ever in the state, and the Arizona Department of Transportation knew going in that the job had tremendous potential to infuriate locals and cross-country travelers. ADOT officials knew they had to plan the project carefully to minimize the disruption and frustration.

The section of I-10 running through Tucson had two critical upgrade requirements, according to ADOT Tucson district engineer Greg Gentsch. "We've known for years that we were going to need to widen the freeway and get the bridges up to standards and clearance," he says.

Widening will add one regular lane and one auxiliary lane each way to total four lanes plus auxiliary lanes and shoulders in both directions. The auxiliary lanes connect each on-ramp with the next off-ramp.

Getting bridges up to standard clearance will provide a major benefit to drivers on the surface streets. Unlike most freeways in the Phoenix area, I-10 in Tucson is an elevated freeway with most cross streets passing under the freeway. Some of those old underpasses have a 14-foot clearance. Only a couple have the standard 17-foot clearance, so traffic requiring 17 feet congregated near those passages.

Three in One

Gentsch says the project was initially planned as three separate two-mile projects. During the planning stage, it became obvious that Tucson was looking at 10 years of non-stop construction. "No one was thrilled with that," notes Gentsch. "We said let's repackage it, and we put it out to the consultant that had two of the three contracts. They merged all three projects together.

"With three stages, you'd spend so much in transition that it would be easier to just close the cross streets, and everybody would have to go around that project for two years, plus or minus. The preparatory work and the tie-up work would run you into a decade of work."

An obvious advantage of combining the projects is that it let the contractor, a joint venture of Kiewit Western and Sundt Construction, keep the cross streets open and put the transitions at the two ends. The obvious disadvantage is that Tucson must get by for three years with a big chunk of its freeway having no on or off ramps.

Gentsch says public opinion in Tucson was initially negative, but "...that turned around pretty quickly when we explained the alternative."

ADOT deputy public involvement director Teresa Wellborn adds, "When we told people this would be three years instead of 10, they liked that. Most people can get their heads around three years, but it's a little harder to get your head around 10 years. You end up with a whole generation who have never known how the freeway is supposed to work."

Some advanced planning in the 1990s helped make the combined project feasible. "They did a project to move the frontage roads out, got the accesses straightened out and basically got the core of this corridor ready," says Gentsch. "So now, the frontage roads are pre-built, and we're not messing with a lot of utilities except on some minor cross streets. It makes it a cleaner deal. We keep the cross streets open, except sometimes at night when we're doing a deck pour or doing bridge demolition."

Kiewit-Sundt has been on board since the beginning in the effort to make the project as painless as possible for the community, according to Gentsch. "Originally, we were going to reduce traffic on the cross streets down to a constant capacity, essentially one-lane through. It did not provide enough capacity on the cross-street, so we worked with the contractor and developed a plan that shifted traffic around pier construction in the center, creating a small football-shaped work island.

"Drilling shafts at the piers was the main issue causing us to limit traffic flow through the project. We came up with a football pattern. It increases capacity to two lanes, instead of one, and Kiewit-Sundt did its drilling on a compressed schedule on weekends. They shut down the whole thing when the volume was low, sent people to the next cross street, got all production done and maintained the schedule. It's one of the main reasons we're on schedule. All drilled shafts were completed in January.

"We're widening the bridges," Gentsch continues. "The new bridges have twice the span in most cases. The football area is sort of a little work island inside. The center pier is in the same place as before."

No Exits?

Closing the ramps creates a six-mile expressway with two lanes in each direction.

In the current phase (Phase Two), all traffic on the northern two-thirds of the project travels on the original northbound side. South of Congress, all traffic is on the southbound side.

When Phase Two is complete, the pattern flip-flops. All traffic will be traveling on the new Phase Two roadway and bridges.

Phase Three should be much easier for the contractors and the public. When the last of the old bridges are demolished, cross street traffic will travel on more lanes, courtesy of the wider spans on the new bridges. Drivers on the expressway will still have only two lanes in each direction, but the lanes will be wider.

As of April, the project was on schedule to move from Phase Two to Phase Three in early July.

Traffic Management

Getting the frontage road set up well ahead of time was not ADOT's only trick to keep the corridor from turning into a traffic nightmare. Prior to closing exits and entrances within the corridor, ADOT built a Traffic Operations Center (TOC) on the west side of I-10 just north of I-19.

The new $15-million TOC has a large room with a wall covered with displays. Remote cameras located all along the corridor feed live images to the displays, showing the traffic flows on the expressway and at intersections of the cross streets and the frontage road. As soon as a traffic interruption occurs — whether it's an accident, a breakdown or simply a higher than usual volume of traffic — TOC personnel can take action to correct the problem.

If it's an accident or breakdown, they dispatch emergency vehicles immediately to clear disabled vehicles. They can also manipulate traffic signals to get traffic moving in congested areas. "That's a significant process," says ADOT project manager Rod Lane. "You can't just turn this light. If we change this one, we automatically cause an issue somewhere else down the road. Making it work smoothly took quite an effort between the city and our people at the TOC."

Lane says the Traffic Operations Center is much more sophisticated than any similar facility ADOT has built. "When we built it, it was the most advanced facility of its type in the country."

The TOC should continue to be a valuable asset after the I-10 project is completed. Exactly who will operate it and how it will work with other systems in Tucson will be determined.

Gentsch notes one other innovative idea that the public relations firm, Gordley Design Group, came up with to help the public get around during construction. "When the design was finalized, the designer contacted Mapquest to have them change how they routed people through here," he says. "If you go to Mapquest and say you want to go to the U of A, it doesn't direct you to the Speedway ramp which no longer exists. It directs you to exit at Prince if you're coming from the north. This is the first project I know of where we did that."


Freeways in urban areas do more than simply move lots of traffic at high speeds. By their nature, they tend to have a negative impact on nearby neighborhoods. They form a barrier that divides cities. They are noisy, and the air around them is usually dirtier than the air further away.

ADOT understands those problems, and has taken steps to minimize them on the new Tucson freeway. The much broader bridge spans make the freeway less of a barrier by providing wider, more appealing passages beneath the roadway. Many parts of the Tucson section of I-10 are very old. The underpasses were low, narrow and confined. They were not inviting to pedestrians.

The new underpasses will be much nicer, with added lanes, lighting and sidewalks. In one critical area, the city of Tucson contributed several million dollars to create an upgrade that will turn the underpass into a feature. The underpass is a few blocks south of Congress in an area the city would like to develop in conjunction with the nearby convention center. Currently, the annual Gem Show sets up major displays on both sides of I-10, but there's no good way for pedestrians to get back and forth.

Gentsch describes the previous underpass as looking like no more than a box culvert. The street passing through from downtown ended almost immediately on the west side at the frontage road. The new underpass will have two vehicle lanes in each direction, plus a broad pedestrian mall. Foot traffic for major events like the Tucson Gem Show will be able to move freely back and forth to attractions on both sides of the freeway.

To address the noise issue, the new freeway's entire length will be paved with rubberized asphalt. That removes the need for sound walls and eliminates the traffic roar of the typical freeway. Areas of the city that have long been considered undesirable because of noise can now be transformed into people magnets.

Visual enhancements to the freeway include artwork and landscaping. "There's a lot of architectural concrete," says Gentsch, "a lot of things like some of the freeways in Scottsdale and Phoenix, where people go 'ooh' when they see them. This project is such a centerpiece for the town and so intertwined with things like the Gem Show and the Santa Cruz River that we felt it was appropriate to go ahead and invest in the enhancements. The freeway runs through some historic neighborhoods and barrios, and the artwork is designed to mesh with the character of those areas."

Given the scope of the Tucson project, the designers and contractors have done a remarkable job of minimizing the negative impact on the community. More than a third of the way through the project, Kiewit-Sundt was more than a month ahead of the original schedule. When it's completed, the I-10 widening won't just be a freeway with a higher capacity. It will be a much friendlier neighbor for the neighborhoods it passes through.


Project Information

Design: Gordley Design Group

Art and Landscape Design: Prince Road to St. Mary's: Wheat Scharff Landscape Architect and artist Carol Clement

St. Mary's to 29th St.: Gresham Beach Architects and artist Gonzalo Espinoza

Contractor: Kiewit-Sundt Joint Venture