The title pretty well sums it up. Although Toronto’s Metrolinx notoriously chose to build a diseasel-powered line from downtown to the airport, saying "we’ll electrify it someday" (but they haven’t), parts of Europe are of course heavily into electrification, but are now taking the final step with battery electrics. "A lithium-ion battery pack is mounted under the train’s floor and is charged while it moves along via overhead lines, using them to both power the train and charge the battery. When the train reaches a stretch of rail with no overhead lines, the battery takes over." Sounds pretty sensible, as long as the range is calculated correctly.