Boring Company Tunnel (Las Vegas Loop)

Elon Musk's answer to traffic: just go underground/Engineering Marvels

The Las Vegas Convention Center Loop is a 2.7 km underground transportation system consisting of twin tunnels with an interior diameter of 3.7 meters. Tesla vehicles carry passengers through the tunnels at up to 56 km/h. The tunnels were bored at a cost significantly lower than typical subway construction, though they also carry far fewer passengers per hour.