>>1463432Because Co-Co's &, to an extent, Co-Bo's run into the exact problem Bogies aim to remedy. And in Japan & Italy, the networks have tighter turns around mountains, meaning Co-Co's are totally unviable due to their inflexibility. Whilst it is possible to articulate the bogies themselves, that's expensive, and Co-Bo's & Bo-Co's run into the issue of different running quality in either direction. Bo-Bo-Bo's are a last resort and not exactly viable in somewhere like the UK & US due to not having to run through mountains most of the route.
