Loetboy made an excellent step-by-step how-to
on making these traffic lights work (and look good). The article has lots of pictures. You can find it here
(in German) or the automatically translated version here
(please don't mind the awful translation).
This is a model of a standard traffic light in N scale (1:160). This model was designed to be fitted with Nano SMD LED's #0402. The light can be mounted on top of a K&S Metals brass pole type TT-62 (ø1.575mm x 0.15mm or 1/16 x .006").
Dimensions for each head:
IN: 0.094 w x 0.179 d x 0.276 h
CM: 0.24 w x 0.454 d x 0.7 h
The space inside is very tight and these SMD's are tiny. This is definitely not a project for beginners.
Before you ask: soldering really isn't one of my skills [/understatement]
so I'm afraid I can't help you with that.