installing directional led lights in a analog locomotive?

[NOPB2013]

does anyone know how to install directional led lights in a analog locomotive? 

[rrinker]

 Aquire diodes. Diagram here.

http://www.mrollins.com/constant.html

LEDs will be automatically directional:

http://www.sumidacrossing.org/ModelTrains/ModelTrainDCC/DCCandLightboards/

 LEDs tend to work poorly on DC, since the voltage varies so much. You need sufficient resistor values to protect the LEDs at full throttle, but this can be too much to let them light up decently at crawling speed. You can combine these two things (leave off the light bulbs from the first circuit) and you will have LED headlights that come on before the loco moves.

                --Randy

[NOPB2013]

thanx. this will help.