LAS VEGAS (AP) — Work has begun to remake one of the busiest interchanges on the busiest freeway in Nevada in a project that officials say will ease access to Allegiant Stadium, T-Mobile Arena and the resort-lined Las Vegas Strip. But officials acknowledge the planned three years of work will create big construction headaches. Gov. Steve Sisolak and U.S. Transportation Secretary Pete Buttigieg marked the start this week of the $305 million upgrade to Interstate 15 and Tropicana Avenue. Officials say the overpass will be demolished and rebuilt — and the freeway will be shut down several times before work ends in 2025. The interchange is a key choke point on the main traffic route from Salt Lake City to Los Angeles.