I'll just add my 2¼ cents worth.
I have three x 3 watt Cree warm white LEDs on my Maxitrak Planet. These are then fitted into 25mm diameter collimators (sort of a lens). The main headlight has a 10° beam, with the two lower ones having 25° beams. They are the correct colour and at night can light the track for over 50m ahead. Smaller diameter ones are available.
The Cree LEDs, collimators and LED drivers (for 12 volt) were found in the Jaycar / Electus catalogue.
As you can see in the daylight photo above, they really look the part.
The above photo was taken at Wandong in 2011 when I had only the one Cree LED headlight temporarily fitted to the Planet. Photo taken, hand held while the train was moving. I think this should demonstrate the effectiveness of the LEDs as headlights.