Last month, Energy Secretary Steven Chu announced that the Department of Energy (DOE) was putting the brakes on research into automotive hydrogen fuel cells because it would take decades to convert to a hydrogen-car economy. But many scientists and energy experts believe Chu made the wrong call. No alternative-vehicle technology will make a major impact on carbon emissions, petroleum use, or anything else within the next 20 years, they say, because it takes longer than that for a new technology to displace what is already on the road. In the long run, they say only two technologies—hydrogen fuel cells and electric vehicles—are capable of getting the job done, and only one variation, plug-in hybrids, will be on the market anytime soon. But the uncertainties with both technologies make it shortsighted to abandon one.