Honda said Wednesday it would put a commercialized self-driving car on the road by 2020, challenging rivals Toyota and Nissan which are also betting on the future of autonomous vehicles. The announcement, ahead of the Tokyo Motor Show next week, comes as the auto giants step on the accelerator in a bid to race past overseas competitors on the next-generation technology. Google has been testing self-driving cars in Silicon Valley, as have U.S.-based Tesla and General Motors, while Nissan has vowed to put an automated car on Japan's highways as soon as 2016. Earlier this month, Toyota unveiled a vehicle that can drive itself along a highway, with plans for a 2020 rollout. The car, a modified Lexus GS, uses sophisticated sensors to navigate roads, merge with traffic and overtake other vehicles.