As has already been said get there earlier to get some nice colour into the sky
also your white balance looks way off
could have done with being shot in Tungsten white balance, what were your settings for this light trail? Aperture, ISO and exposure
You may find giving my guide to light trails a read helpful, there is a link in my signature
Come and do some on my closest motorway
the M45 I could often do a 5 minute exposure and get only a single vehicle in there
but then I have the M1, M6, M40, M69 that all have a tonne of traffic
Matt
MWHCVT