What’s that massive structure being built off I-15 near Tropicana?

If you have driven on Interstate 15 near Tropicana Avenue in recent weeks, it is likely that a large structure being built along the southbound lanes has caught your attention.

The under construction piece of infrastructure is a new on-ramp which is part of the $305 million, yearslong I-15-Tropicana project.

Once completed, the on-ramp will span half-a-mile in length, leading motorists from Tropicana onto I-15 southbound, according to Nevada Department of Transportation spokeswoman Kelsey McFarland. Of the lengthy on-ramp, the bridge portion of the ramp being built will be 650 feet long and stand 16.5 feet above the street that will travel under it.

The new on-ramp will feature three lanes at the entrance, which then merge into one lane after a ramp meter on the collector-distributor south road — a road that carries traffic from a less busier road leading to a more active arterial road. Aside from I-15 access, the collector distributor road will also provide motorists access to the 215 Beltway.

The elevated Tropicana to I-15 on-ramp is needed to allow for a reconfigured Dean Martin Drive to run beneath it, letting drivers skip the current signalized intersection at Tropicana, providing a smoother traffic flow to and from Allegiant Stadium and beyond.

“It also enables westbound Tropicana travelers to head south on Dean Martin to Allegiant Stadium,”McFarland said. “Due to the significant grade difference in Tropicana’s median, left turns at the Tropicana and Dean Martin intersection will no longer be allowed once the project is complete.”

Dean Martin will remain two lanes in each direction once the road is reconfigured underneath Tropicana.

The already completed and opened I-15 Harmon Avenue half interchange allows for motorists traveling on I-15 northbound to Harmon, to access Dean Martin to the west, or the Las Vegas Strip to the east. The Harmon off-ramp to I-15 northbound provides another way to access the freeway from the stadium or resort corridor.

Work on the bridge will carry on into next year and be open to traffic at the time of substantial completion, which is slated to occur near the end of February, according to NDOT’s project schedule.

The project also includes reconstructing and raising of the Tropicana interchange by widening the bridge over I-15 and the on-and-off-ramps. The I-15 southbound to Tropicana eastbound flyover ramp was partially reconstructed. The I-15 northbound off-ramp to Arena Drive, to T-Mobile Arena, will be widened, with pedestrian access to both T-Mobile Arena and Dean Martin for Allegiant Stadium also planned.

Contact Mick Akers at makers@reviewjournal.com or 702-387-2920. Follow @mickakers on X.