Oil headlamps on GM diesels, what was the point?

[minister_for_hardship]

Noticed a few photos going around of new and nearly new GM diesels (already equipped with electric lighting) sporting steam-era oil headlamps.

 

Also there are CIE publicity shots of a 001 in SuperTrain garb and modern electric lights also carrying white-painted oil lamps.

 

When did oil headlamps cease to be used? Not counting RPSI specials and similar here.

[Mayner]

The oil headlamps were mainly to assist the signal man to identify the class of an approaching train, though most GSR/CIE mainline passenger and goods trains used to display the UK Express Passenger code (a lamp over each buffer) https://en.wikipedia.org/wiki/Train_reporting_number#Headcodes.

 

The practice of using oil headlamps seems to have died out in the early 1970s when CIE introduced a computerised train control and the 1st stages of widespread CTC.

Edited August 15, 2015 by Mayner