As others have suggested, running trains overnight hugely complicates routine maintenance. When people are working on the line, any train movements will hugely

As others have suggested, running trains overnight hugely complicates routine maintenance. When people are working on the line, any train movements will hugely increase the risk profile. The more sensible option is generally night buses, which are considerably less expensive. The London Underground runs a limited night service on some lines on Friday and Saturday nights, but London has a fairly extensive night bus service.