For reasons I haven’t quite figured out, there seems to be a considerable number of double-header freights trains passing by all the time – we live close enough to see plenty of freight trains passing. Other than the obvious under-powered reasons, most of these double-headers and ‘bankers‘ – you have one at the back pushing. Sometimes the formation is a coupled bank engine, othertimes they are uncoupled; The tracks have little or no gradient to bother the hauling loco, even in the surrounding area. So the only plausible explanation is simply too many underpowered locos