Kearney patented an innovative underground monorail railway system, the Kearney High-Speed Tube, which used the effects of gravity to enhance acceleration and deceleration and reduce power consumption with a "roller coaster" type of motion; from shallow sub-surface stations, deep-level tube tunnels would fall away at a 1-in-7 gradient, enabling underground trains to reach an estimated 60 mph before slowing down as they climbed to the next station.