It was going to happen sooner or later. And it was later than some drivers would have wanted. But here in August we’ve bid farewell to the two roundabouts on separate ends of the Happy Valley Road bridge that traveled over Interstate 17 in north Phoenix.

In fact, we also said goodbye in recent months to the old Happy Valley bridge that used to connect to those circular roundabouts. The demolition of the old bridge and removal of the roundabouts have now taken place as part of the construction of a much larger, much more modern bridge and diverging diamond interchange at I-17 and Happy Valley Road.

While the old Happy Valley roundabouts operated for some two decades and certainly were criticized by many a local driver over time, there is another side of the story. In their defense, the roundabouts did what they were designed to do. 

In the late 90s, there just wasn’t funding available to pay for a larger and wider bridge to carry Happy Valley Road over the freeway. In order to make the I-17 interchange still work with local projects that were widening Happy Valley Road as it approached the freeway, ADOT researched alternatives and studied the use of roundabouts in other parts of the country.

The Happy Valley roundabouts allowed for the need for traffic on a wider Happy Valley Road to transition down onto the existing and narrower two-lane bridge over the freeway. That would have been much more difficult, if not impossible, to do with traffic signal intersections. 

The roundabouts were always designed as an interim measure until such time when enough regional funding was available to construct a new freeway interchange. That happened as part of the Regional Transportation Plan for the Phoenix area that was approved by county voters in 2004. The plan allowed for the $50 million project that is now scheduled for completion this fall.

Crews have been building the new diverging diamond at I-17 and Happy Valley Road as well as a more traditional diamond interchange at Pinnacle Peak Road. We’ll have more about the diverging diamond in an upcoming blog.

Although the time and funding had come to replace the Happy Valley roundabouts, there are plenty of examples where roundabouts will continue to safely move traffic. That includes highway intersections in the Verde Valley and beyond. If you’re using them, please remember to follow the rules of the roundabout, including slowing down as you approach and yielding to traffic already in the circle.

The use of thermal detection cameras to spot wrong-way vehicles on freeway off-ramps along Phoenix-area freeways will continue to grow, especially after the cameras have worked well as part of a pilot project along Interstate 17. 

As one example, you can look ahead to significant stretches of Loop 101 currently being widened to also have the thermal camera wrong-way vehicle alert technology added.

ADOT began operating the I-17 alert system in January 2018 along the 15-mile stretch of the Black Canyon Freeway between the I-10 “Stack” interchange near downtown and the Loop 101 interchange in the north Valley.

Thermal cameras were the key components installed to detect wrong way vehicles and immediately alert both ADOT and the Arizona Department of Public Safety so troopers can respond faster than waiting for 911 calls and operators in the ADOT Traffic Operations Center can quickly post warning messages for other drivers with just the push of a button.

ADOT’s I-17 system, a first-in-the-nation effort, was designed to reduce the risks created by often-impaired wrong-way drivers. Our assessment found the thermal cameras are very reliable in detecting those vehicles. 

ADOT’s look at data from the I-17 project shows more than 100 wrong-way drivers set off alerts when thermal cameras detected their vehicles. More than 85 percent of the drivers made a self-correcting turn on an exit ramp without entering the freeway. The I-17 system includes specialized background-illuminated signs along off-ramps that light up toward a potential wrong-way driver in an effort to get that driver’s attention.

While the I-17 system went through testing, ADOT converted thermal cameras already in use for traffic signal timing so they also can detect wrong-way vehicles. Cameras at Loop 101 interchanges between 59th Avenue and Bell Road in the northwest Valley were among those set for such detections.

The majority of interchanges along the new Loop 202 South Mountain Freeway have thermal cameras set up to send wrong-way vehicle alerts to ADOT and AZDPS. Wrong-way vehicle technology projects are underway along Loop 303 from I-10 in the West Valley on up to the I-17 interchange in north Phoenix. 

Thermal cameras also will be in place at off-ramps along the Loop 101 Price Freeway between Baseline Road and Loop 202 in Chandler and the Loop 101 Pima Freeway between I-17 and Princess Drive in the north Valley. The wrong-way vehicle alert technology was added to the ongoing widening projects taking place in those areas.

ADOT will pursue opportunities to deploy thermal cameras along other Valley freeways as well as state highways, starting with rural interstates, as funding and necessary fiber-optic infrastructure become available. ADOT’s assessment of the I-17 pilot system also recommends installing the illuminated, flashing “Wrong Way” signs at urban locations as funding allows.

While we will continue to stress that technology can’t keep a wrong-way driver from getting behind the wheel, nor can it physically prevent a crash, it continues to show that it is an important tool to use to alert law enforcement and warn other freeway drivers when a wrong-way vehicle is detected.

If you're a driver whose travel takes you along Interstate 17 near Central Avenue south of downtown Phoenix, you've likely noticed some changes now that bridge resconstruction work has started in that area.

As we told you about a few weeks ago, we have kicked off our project to replace the aging Central Avenue bridge. The new structure will raise the clearance from 14 to 16 feet, which better allows for modern commercial vehicles, trailer-towed construction equipment and the coming Central Avenue light rail extension. That's a slideshow of the beginning of the $13.5 million replacement project you can see to the right. You can also check out the project's page on our website to learn more.

But after this weekend, you'll notice more changes.

Starting tonight,  the southbound freeway will be closed at Seventh Avenue while northbound will be closed between the Interstate 10 "Split" and Seventh Avenue. When it reopens early Monday morning, traffic will have been switched to using just the northbound bridge, so the southbound bridge can be reconsructed. Once that wraps up early next year, traffic will be switched to the southbound structure so the northbound bridge can be similarly improved. While the project continues, outside of other needed closures or restrictions, we will keep two I-17 lanes open in both directions.

But while we are keeping lanes open, drivers should continue to budget extra time if their commutes take them through the work zone. You can also consider using alternate routes, such as I-10 through downtown Phoenix.

The whole project is scheduled to be wrapped up in fall 2021, and we are confident you will notice and appreciate this improvement.

Work to build a new, larger Interstate 17 bridge over Central Avenue south of downtown Phoenix is now underway as ADOT and partner agencies look ahead to improvements beyond the freeway itself. But the progress also means drivers should consider using alternate routes, including Interstate 10, while the bridge reconstruction requires I-17 lane closures.

The current I-17 bridge, dating back to 1962, provides clearance of just under 14 feet for vehicles passing underneath it along Central Avenue. ADOT’s $13.5 million project will provide a new structure with clearance of approximately 16 feet, which certainly helps with the movement of today’s larger commercial vehicles as well as the variety of construction equipment that is often hauled on trailers.

Meanwhile, the timing of the I-17 bridge reconstruction has been coordinated with the city of Phoenix and Valley Metro, since the modernized bridge will allow the future Central Avenue light rail line to extend south of the downtown area.

If you’re a driver who uses the stretch of I-17 between the I-10 “Split” interchange near Phoenix Sky Harbor International Airport and the I-10 “Stack” south of McDowell Road, you should plan ahead for lane restrictions now that a work zone is established in the area between Seventh Street and Seventh Avenue.

I-17 is now narrowed to two lanes in both directions approaching Central Avenue. By early June, additional work will be done to temporarily switch I-17 traffic to one side of the freeway so that the first half of the new bridge can be built. The freeway will operate with two lanes in each direction outside of times when closures or other restrictions are needed for work, mostly during overnight hours or on some weekends. That’s why it might be a good idea to use I-10 as a way to travel beyond the I-17 bridge construction zone.

The entire project is scheduled for completion in fall 2021. Additional information is available at azdot.gov/I17CentralBridge.

When finished, the new I-17 bridge will have been widened enough to accommodate a future project to add auxiliary, or merge, lanes along the right shoulder of I-17 in both directions between the on- and off-ramps at Seventh Street and Seventh Avenue.

It’s another step forward in what regional planners see as major improvements to help manage the traffic needs along one of the original backbone freeways in the Valley of the Sun.