Moving Quickly: Northaven Trail Bridge 

By Kira Larson, project manager on the TxDOT Northaven Trail Bridge

The newly built Northaven Trail Bridge in North Dallas spans the busy eight-lane US 75/North Central Expressway, providing a safe crossing for users, extending recreational opportunities, and expanding access to alternative methods of transportation. The bridge exemplifies the highest standards of thoughtful design, thorough project planning and successful teamwork, which culminated in a successful move and installation over US 75 in just one weekend. 

The bridge provides a long-awaited connection for multiple regional bicycle and pedestrian trails—specifically, the popular Northaven Trail on the west side of US 75 and the Cottonwood Creek and White Rock Creek trails on the east side.

The Texas Department of Transportation (TxDOT), the bridge’s owner, called the bridge “a regional example of the positive benefits of appropriate location and design aesthetics for future bicycle and pedestrian trails and amenities.”

Why was the Northaven Trail Bridge project important to TxDOT?

The Northaven, Cottonwood Creek and White Rock Creek trails are heavily used and end on either side of US 75. To cross and access the trails on the other side of the highway—one of the busiest roadways in Texas—cyclists and pedestrians previously had to use a connection under the highway main lanes that did not have updated drainage or lighting. TxDOT wanted to remedy this by establishing an easily accessible trail connection across the highway.

What were TxDOT’s project goals? What challenges was the project designed to address?

Beyond creating a safe connection across US 75, a key project goal was to deliver the Northaven Trail Bridge with minimal impact to the traveling public. TxDOT required that either a frontage road or a lane both northbound and southbound on US 75 remain open throughout construction and that any main lane closure period be limited to Saturday overnight. This allowed for roughly 250,000 vehicles to continue daily without disruption. 

What was HNTB’s involvement in the project?

Working with TxDOT, HNTB served as conceptual designer, engineer of record and construction phase services provider on the project. The firm also participated in public outreach to stakeholders, including trail users, communities, and organizations located near the trails, to gather input on the community’s needs and wants.

What design considerations were key to developing plans for this bridge? How is this bridge an example of industry innovation?

HNTB designed a structure that was a lightweight, redundant system that could be safely transported to its final location on self-propelled modular transporters (SPMTs). This accommodated accelerated bridge construction, which allowed the bridge to be built off-site and moved into its final location overnight.

In addition, Lee Kleinman, the former Dallas City Council member who originally proposed the idea for a bridge over the highway in the early 2000s, was inspired by the idea of representing a bicycle wheel in the bridge’s design. The original network tied arch concept for the main span was developed in 2017 by HNTB to reflect all stakeholder feedback. The network cable arrangement greatly reduces bending in the arch and deck and, in this case, has the added benefit of being reminiscent of the spokes on a bike’s wheel, as Kleinman envisioned.

The final design adhered closely to some of the early sketches and modeling concepts developed from conversations with the City of Dallas and other stakeholders.

“Often, an early concept design and what is ultimately built are quite different,” said Tom Kramer, HNTB project manager during the plans, specifications and estimates portion of the project. “In this case, we developed a unique initial concept and saw it all the way through to completion.”

What is unique about this bridge?

The site designated for the Northaven Trail Bridge required the bridge to be built at an angle across the eight lanes of US 75. The design team decided to create a unique tied arch structure that accommodates the skew and gives the bridge a soft, reverse “S” curve.

With tied arches, a bridge deck normally needs to be straight. Within the Northaven Trail Bridge’s S-curve, however, straight post-tensioning strands run through the deck, acting as the tie. 

The structure is the only known network tied arch bridge in the world with a doubly curved tie. The bridge also has skewed ends, making it an exceedingly complex structure not seen elsewhere in the world.

What challenges did the project encounter, and how did HNTB, the contractor and the client overcome them?

To meet the challenge of keeping US 75 traffic moving throughout the Northaven Trail Bridge project, the team designed for accelerated bridge construction techniques, which allowed the bridge to be built off-site and moved into place. The bridge deck, cables, and arch were constructed as a single structure on timber shoring in the back parking lot of a furniture store to the east of the highway. Other elements, like bridge columns and approaches, were built in place at the highway.

The bridge move, a first for TxDOT’s Dallas district, was achieved over a single weekend. Utilizing remote-controlled SPMTs, the bridge was transported from its off-site location on a Friday in September 2023 and positioned roadside to US 75/North Central Expressway. On Saturday, the SPMTs pivoted the 201-foot-long, 800,000-pound structure from its parallel position before relying on bridge gantries to place the bridge in its final location. TxDOT and HNTB team members stood side-by-side on US 75 in the middle of that night, watching the Northaven Trail Bridge with its 50-foot-tall arch be driven into place over the highway.

While highway traffic was minimized for a few hours overnight, the project team was able to ensure that US 75 was never fully closed to travelers. By Sunday afternoon, the bridge was in place and all US 75 lanes were once again open.

The bridge move took about 20 hours, requiring only about 14 hours of full closures of the main lanes. During that time, traffic was diverted to the adjacent frontage road, leaving a lane of traffic always open to drivers during the move. After the bridge was installed, final tie-ins were completed before the span opened to the public.

How does the completed project fulfill the client’s and the community’s goals?

The public was deeply invested in the project and the bridge has been celebrated and heavily used since it opened. The project included dedicated parking on the west side of the bridge for anyone who wants to drive to the site and use the spot as a trailhead. The parking area is designed as a space that can accommodate food trucks, the start of a race, or other events, enhancing the area’s potential use as a community space.

Because the bridge’s arch is its most identifiable feature, it already has become a defining landmark that serves as a gateway into North Dallas. Feedback provided to TxDOT reveals the benefits the bridge has already delivered to the community and confirms that the public appreciates the project’s grandeur.

The day the Northaven Trail Bridge opened, “tons of people were using it,” said TxDOT project manager Nathan Petter. “The public was so vested in this wonderful project. The use we immediately witnessed showcases the project’s success.”

What are the aspects you would like readers to know or remember about this bridge project?

The Northaven Trail Bridge used accelerated bridge construction, a methodology that allowed the bridge to be built near the roadway and moved into place over the eight lanes of US 75 using SPMTs. This technology facilitated the project team’s ability to meet TxDOT’s goal of never fully closing US 75 to travelers.

The design team addressed the unique geometry at the site where the bridge now stands by designing a softly curved bridge deck that uses a network tied arch. The bridge’s network cable arrangement, a term used when the cables cross one another more than once, allows the arch and the bridge to be very thin while still being resilient to accidental overloads.

The Northaven Trail Bridge is a complex structure that is the only known network tied arch bridge in the world with a doubly-curved tie.