The Prius is the first incarnation of Toyota's Hybrid System offered to the public, but the principles upon which it is built could easily extend to other vehicle sizes, shapes, and applications. At the 1999 Tokyo Motor Show, Toyota unveiled the HV-M4, a 4-wheel-drive minivan that employs one possible adaptation of current hybrid technology. The vehicle adds a second electric motor that can drive its rear axle, while a computer-controlled power distribution system ensures that the vehicle maintains maximum traction under all road conditions. What’s more, the completely electrical power connection to the rear axle eliminates the need for a propeller shaft to connect the front and rear axles, as in conventional 4-wheel-drive vehicles, freeing up space in the vehicle interior. Of course, the HV-M4 also boasts much better fuel economy than conventional vehicles in its class.
Making the Most of Motive Force
Hybrids to Come