Peter47 - In Luton's case whilst the parallel taxiway doesn't extend to the runway ends most departures which are not performance limited can accept the reduced distance when departing from an intersection so avoiding a backtrack of the runway to the full length. I believe in USA airports like SFO use the automated "runway status lights" system (red lights) which hopefully mitigates runway conflict issues. There's a video on YouTube about Paris CDG runways status lights which may be the only European airport to provide them.