The Boring Company
Original promise - 2016. A "hyperloop" within large cities with multiple "off ramps" or "tributaries", enabling new rapid transportation at low cost, with the ability to entice millions onto public transport because it would be much more efficient and convenient. It would allow anyone to drive their own electric vehicle to the tunnel, turn off the engine, and let the tunnel do the work of moving the vehicle. Boring Co. had designed a new a new tunnel borer which would be able to bore wide tunnels at faster speeds than all of their competition.
Amended promise - a tunnel with extra smooth concrete to enable high speed travel by electric vehicles beneath cities. They bought a borer from a competitor.
Reality - a poorly designed 1.3 mile long, very narrow, single-lane tunnel between the convention center and a hotel in Las Vegas designed for chauffeured Tesla vehicles only. The trip takes 4 minutes if there's no tunnel traffic, apparently 20 minutes during times of peak demand. That compares to a 5 minute drive on surface streets and a 19 minute walk on area surface streets that are highly unfriendly to pedestrians. The tunnel and chauffeurs work only on days when there's a scheduled convention.