At the annual Detroit auto show today, Ford announced plans to introduce a new technology to Ford Explorers in 2004 to raise their fuel efficiency 42 percent, from 19 to 27 miles per gallon. The electric technology, which will cost willing buyers less than $1,000 extra, will boost fuel efficiency and lower emissions by automatically shutting down a gasoline engine when the vehicle stops and then restarting it when the driver steps on the accelerator. Meanwhile, General Motors says it will begin offering a wide range of vehicles powered by hybrid gas-electric engines in 2004. Many observers credit the automakers’ shift to the requirement in California that a growing number of low-emissions vehicles be sold in the state beginning with the 2003 model year, and to pressure by Honda and Toyota, which have already begun to use hybrid technologies in their cars. In other news, GM, Toyota, and ExxonMobil are joining together to develop fuel cells that use hydrogen extracted from gasoline, an energy source that the companies believe will serve a transition fuel as fuel cells enter the mainstream.