Options included internal combustion engines fueled by petrol, diesel, propane, or natural gas; hybrid vehicles, plug-in hybrids, fuel cell vehicles fueled by hydrogen and all electric cars. Fueled vehicles seemed to have the short term advantage due to the limited range and high cost of batteries. Some options required construction of a network of fueling or charging stations.[1] With no compelling advantage for any particular option car makers pursued parallel development tracks using a variety of options.