A dual-mode transport system is one in which specialized vehicles travel under driver control on the street, but can also dock to a guideway (usually a monorail) for automated travel over an extended distance. The concept of dual-mode systems started gaining momentum in the mid-1970s. Palle R. Jensen, an inventor from Denmark, has been developing his "Rapid Urban Flexible" (RUF) system since 1988. The RUF system consists of electric vehicles designed with a triangular groove along the base, allowing the vehicle to dock firmly with the triangular monorail. Because the rail requires just over 8 square feet of operating space, Jensen asserts that it could easily be placed along existing traffic corridors in order to reduce total cost of implementation. A computer system guides entry onto, and exit from, the monorail at about 20 mph—and also controls the vehicles as they move along it, coupling them into aerodynamic "trains" which reduce energy consumption and can reach estimated top speeds of 125 mph. The monorail's shape makes derailments impossible, so this system is much safer than traditional driver-controlled travel. While on the monorail, the vehicles' batteries recharge. This means that the vehicle has maximum battery life for driver-controlled travel to any destination not located along the monorail's route.
Barriers to the implementation of the RUF system include the high cost of building the infrastructure--estimated to be upwards of a billion dollars-- and the limited availability of the specialized vehicles required. Still, the benefits of such a system might be enough to convince cities to consider the RUF dual-mode transport system as a viable option for their communities.
Find out more at the RUF website: http://www.ruf.dk/