This month, a $33.3 million project to improve safety and traffic flow at one of the busiest traffic interchanges in Las Cruces, New Mexico, reached the halfway mark of its estimated 18-month construction schedule. The I-25/University Avenue Project, led by the New Mexico Department of Transportation (NMDOT), has been underway since early January and is anticipated to last until summer 2021. It is being built in seven phases and includes work on Interstate 25, University Avenue, and Triviz Drive.

A design-bid-build approach is being used to deliver these roadway improvements, with Molzen-Corbin & Associates (Molzen-Corbin) serving as the lead design firm and La Calerita Construction, LLC as the prime contractor. The primary objectives are to add capacity at I-25’s southbound off-ramp leading to New Mexico State University (NMSU), reduce congestion and weaving, provide direct connections to the Pan American Center parking lots, build roundabouts to improve local traffic flow, and enhance multimodal transportation options for bicyclists and pedestrians.

Currently, drivers heading southbound on I-25 must exit onto University Avenue to access Triviz Drive, and those going south on Triviz Drive must cross University Avenue to continue their journeys on that road. But once the I-25/University Avenue Project is completed, travelers will have an easier way to access destinations around Triviz Drive, like NMSU, because they will no longer have to use University Avenue.

It is important to note that NMDOT is spearheading this undertaking in cooperation with the City of Las Cruces and NMSU. “This project is unique in that NMDOT owns the interstate and the I-25/University Avenue interchange, the city owns the north side of Triviz Drive, and NMSU owns the south side of Triviz Drive,” says Wyatt Kartchner, Vice President, Molzen-Corbin. He notes that certain infrastructure elements such as lighting, landscaping, and traffic signals will be funded or maintained by NMSU and the city.

Escalating traffic volumes over the next decade underscore the vital need for these roadway upgrades. By 2030, average daily traffic counts are projected to reach 61,400 on I-25 and 33,000 on University Avenue, according to NMDOT spokespersons.

The crux of this project is improving the I-25/University Avenue interchange, which was originally built in 1966, reconstructed in 1988, then rehabbed in 2012. The interchange, which provides access to NMSU and other area destinations, experiences significant morning rush hour traffic. Consequently, vehicles tend to back up onto I-25, which increases the likelihood of crashes.

“Traffic will back up as it is trying to turn right, particularly on the southbound exit ramp, and then at the next intersection it quickly tries to turn left to access the campus,” Kartchner explains. “With the improved interchange configuration, we’re eliminating this weaving movement by creating a dedicated lane for campus-bound travelers.”

Two southbound off-ramps will support this updated configuration. One ramp will lead to a signalized intersection and provide access to University Avenue, and the second will cross underneath University Avenue and provide direct access into the NMSU campus via a roundabout.

In 2012, the original project proposal provided by civil engineering firm Gannett Fleming West listed 20-plus design alternatives. In subsequent years various creative engineering approaches were considered, along with input from local businesses and residents, during efforts to elevate the project’s conceptual design and achieve the best value for the community. Resultingly, the recommended design alternative has a host of optimizations, one of which is offsetting construction of the replacement University Avenue bridge over I-25 to help improve the traffic management strategy.

“During the design phase, one of the key things that we wanted to maintain as much as possible is two lanes of traffic in each direction on both I-25 and University Avenue,” Kartchner says. “To accomplish this, we offset the new bridge about 70 feet to the north of the existing bridge, which allows for about two-thirds of the new structure to be built without disturbing traffic on the existing alignment. It also helped with the geometry of the roundabout on the NMSU side of the roadway and also reduced the amount of right of way (ROW) necessary for this project, which saved costs on ROW acquisition.”

The new two-span bridge, just over 184 feet long and measuring 111 feet wide, will be made of precast concrete and contain 14 girders. It will have bicycle lanes and sidewalks as well as four travel lanes (two in each direction) for university traffic, along with a left-turn lane to access I-25 south and a right-turn lane to access I-25 north.

While a new bridge connecting southbound I-25 travelers directly to the NMSU campus will solve many traffic snarls, Molzen-Corbin saw a valuable opportunity to alleviate congestion in the area even further. The firm proposed a new underpass beneath University Avenue to link the north and south portions of Triviz Drive, a major local roadway, which NMDOT approved as part of the final design package.

“This added component helps to free up the intersection at University Avenue and Triviz Drive, and also allows for another access point that includes access for pedestrians and bicyclists as we have a multimodal trail that goes through the entire project,” Kartchner says. The new two-span, prestressed concrete structure will have 14 girders and measure 230 feet long and 111 feet wide. It will carry two lanes of traffic in each direction along University Avenue and contain a dedicated right-turn lane as well as bicycle lanes and sidewalks.

Additionally, the scope of work includes erecting a new bridge over the Pan American Center to relieve traffic congestion at the University Avenue/Triviz Drive intersection and extending the Triviz Multi-Use Path (locally known as the Triviz Trail) to the new NMSU trail system.

Another key design element is the project’s incorporation of single-lane roundabouts – one on each side of the University Avenue/Triviz Road underpass – to help local traffic flow more efficiently and smoothly, which consequently reduces vehicle emissions and fuel consumption.

Multiple studies have shown that these circular intersections are much safer than traditional stop sign or signal-controlled intersections. This is a major benefit to Las Cruces drivers, given that roughly one-quarter of all traffic fatalities in the United States are associated with intersections, according to the latest Federal Highway Administration data.

“Roundabouts are becoming more popular in New Mexico and in the U.S. in general; however, they aren’t a one-size-fits-all solution,” Kartchner cautions. “They did work on this project, but there are locations where they don’t work as well.” Situations where roundabouts are not ideal include areas with heavy left-turn volumes or large pedestrian volumes, and places where drivers are not familiar with navigating roundabouts.

On the I-25/University Avenue Project, the northern roundabout will look similar to the existing roundabout at the north end of Main Street in downtown Las Cruces, except it will be more intuitively designed and thus easier for drivers to navigate, according to project spokespersons. It will offer motorists the option to continue traveling either on Triviz Drive or toward the southern roundabout under University Avenue. The larger roundabout to the south will offer drivers four options: head back north of Triviz Drive with a free-flow movement; head west on Triviz Drive to access Arrowhead Drive; head south of Triviz Drive to Wells Street; or keep going to access I-25 south.

Numerous retaining walls are being installed on the project, including 18 mechanically stabilized earth (MSE) walls totaling approximately 35,000 square feet. The form liners for these structures, which range in height from 6 to nearly 30 feet, are being hand-sculpted by artists to fit a certain aesthetic reflecting the regional identity, culture, and history.

Coordinating project activities around the phased delivery of the intricately designed MSE wall panels is one of the most challenging aspects of the entire project, as the sheer number of custom form liners requires a longer lead time.

“The manufacturing process of the form liners is time consuming,” remarks NMDOT Project Manager Ryan Tafoya. “In order to keep this project on schedule, the contractor has mixed construction phases.” This approach allows crews to work in areas not requiring wall panels while waiting for the material deliveries, which keeps the project progressing.

The MSE walls and bridge structures are being customized to feature the designs of local artist Collette Marie, who was selected through a competitive process to create a look and feel that would make the project – heralded as a “gateway” from southbound I-25 to Las Cruces, the community, and NMSU – unique and memorable.

Marie’s artistic vision is an homage to the region’s agricultural roots and also depicts growth and learning in the academic world. As part of an “Earth and Seed” concept, she is using larger-than-life plants and animals to create an immersive art experience. These stunning exhibits will include creatures such as the New Mexico whiptail lizard (the state reptile) and the melodious Song Sparrow as well as plants and crops including ocotillo, agave, onions, pecans, and cotton.

Sustainability is another major component of the project, which is the first in NMDOT history to use the Envision program to guide its infrastructure objectives. “Envision is a sustainability rating system that is very similar to LEED, but is utilized for horizontal construction rather than vertical,” Kartchner elaborates.

The Envision rating system aims to provide a consistent, consensus-based framework for assessing sustainability and resilience in infrastructure. Administered through the Institute for Sustainable Infrastructure, the program has 64 indicators, called credits, organized around five categories: quality of life, leadership, resource allocation, natural world, and climate and resilience.

According to Kartchner, the Envision program aligns very well with the objectives outlined in “The New Mexico 2040 Plan,” which is NMDOT’s long-range, multimodal transportation plan designed to support a robust economy, foster healthy communities, and protect the state’s environment and unique cultures.

The I-25/University Avenue Project – designed to keep traffic flowing and functioning smoothly for the next two decades – aims to earn an Envision Gold rating. To reach this goal, the project is recycling and repurposing old concrete and asphalt, utilizing harvested rainwater and various energy-efficient materials, extending the Triviz Trail system as part of NMDOT’s sustainability plan, plus much more.

Currently, the Envision program includes 84 verified projects representing a total investment of $22.5 billion, with another 103 registered projects awaiting verification. “NMDOT does a really good job of incorporating sustainability goals as part of its standard approach to projects. But by following the Envision process exactly as it’s laid out, we could actually give the DOT some recognition for steps it is already taking,” Kartchner states.