Below is a pic of a bike for R'Ex when he gets old. It will compliment his Prius in that it has electric drive and regenerative braking. The couple on the bike is Bill and Jan who own Santana Tandems. According to Bill, this is a prototype and if tests pan out, it may become a Santana offering. It has 3 speed rear hub with 3 levels of power boost. And on descents, there is regenerative braking as soon as the brakes are applied. The electric drive package adds about 20 pounds to the bike and the estimated cost is $2000 for the option.