Trains

This is inaccurate for the UK. A lot of the lines have tunnels (e.g. along to Holyhead) or have geography (e.g. CVL) or planning issues that makes electrification of the whole line much more expensive. By contrast, if you have bi or trimodal trains you can electrify the easy parts while avoiding the high cost parts, which means you can roll out the electrification of the easy bits so much quicker.