PH Origins: Auto-dipping headlights


The inability of drivers to correctly deploy dipped or main-beam illumination is not a new problem. "It has not been possible to get drivers to use their beams properly" stated engineer George Onksen - in a paper published in 1953.

Onksen, who was a research engineer for General Motors, had observed that drivers frequently demonstrated two failings when it came to beam control. 'Some do not depress to the lower beam when meeting another car,' he noted, 'and others drive continuously on their lower beams.'

This was causing two problems. Firstly, drivers were being blinded by the harsh glare of oncoming un-dipped lights - an issue that was becoming increasingly troublesome as both headlight output and the number of cars on the road increased. Secondly, the drivers who just used dipped beams weren't benefitting from the additional illumination available to them.

Both were notable safety issues. Fortunately, GM was entering its golden era in the early 1950s, raking in vast amounts of money and developing new technology - such as air conditioning - at a terrific rate of knots. The company, which had showcased autonomous car concepts since 1939, was also investing in simplifying and automating the process of driving.

Consequently, an automatic headlight control device seemed a logical way of resolving improper beam usage. After all, no other method or tactic seemed reliable or effective enough; 'It is hopeless to get drivers to pay more attention to their driving,' concluded Onksen, 'either through education or law enforcement.'


The concept of an automatic system wasn't a new one, according to GM's own reports and similar patents submitted in the mid-1940s, but reliable, accurate systems had never been built. GM's Guide Lamp Division, however, came up with a solution to the problem in the early 1950s.

Originally, the Guide Lamp Division had been a standalone entity called the Guide Motor Lamp Company. It had been founded in 1906 and manufactured lamps for early automobiles, before being bought out by GM in August 1928. Besides producing lights - and weapons - during World War II, it continued to deliver illumination-related innovations, reportedly including the first plastic light lenses.

The research team at Guide, including Onksen, had subsequently been working on automatic light operation; the team was attempting to come up with a system that would automatically dip the lights when it sensed an oncoming bright light, then to switch back to main beam once the light had passed.

Previous trial set-ups had relied on photoelectric cells but these reputedly proved unreliable due to low sensitivity levels. One car might detect the lights of the other oncoming car and dip its lights, at which point the other car's auto-dipping system wouldn't respond to the dimmer source until the cars were so close as for its effect to be meaningless.


Guide's successful change of tack was to instead use the increasingly common photomultiplier tube. These, a class of light-sensing vacuum tube, were incredibly sensitive and ideal for quickly picking out oncoming lights at a suitable range.

With these to hand, a significant amount of development led to the specification and construction of a production auto-dipping system, called the Autronic-Eye, which was introduced on 1952 Oldsmobiles and Cadillacs.

The system featured a dash-mounted, space age-styled phototube unit, which looked through the windscreen. It activated when the driver switched on the lights and the high voltage required to operate it was supplied by a transformer that put out 1150 volts. Signals from the phototube were sent to an amplifier and relay assembly, which would then toggle automatically between upper and lower beams.

One key element was the assembly's integrated sensitivity control, which permitted the Autronic-Eye to detect far-off lights and dip and hold correctly; it was configured to an optimum sensitivity that granted correct distance dimming then, once dimmed, would become ten times as sensitive - preventing it from switching back to high beams if the oncoming car had also dimmed its lights

The Autronic-Eye was then made available to other GM brands, including Pontiac and Buick, in 1953; other companies are also said to have later made use of the same hardware, including Lincoln in 1957 and Chrysler in 1959.


The system was offered up until 1960, at which point it was updated and rebranded Guide-Matic. A new 'safety salute' feature was added, which - when an oncoming car was detected - lit up the dipped lights in conjunction with dimmed main beams momentarily. The aim was to further grab the attention of the other driver, showing off the Guide-Matic technology and prompting them to dip their lights if they hadn't already.

The safety salute hardware proved unreliable, however, and was quickly disabled by dealers and withdrawn from service. The Cadillac Guide-Matic option, though, ran until 1988 before later being replaced by a more modern set-up, dubbed Intellibeam, in the 2005 Cadillac STS; a camera-based system also arrived on the market in 2005, in the Jeep Grand Cherokee, and this type is common today.

Besides continuing to upgrade and develop the Autronic-Eye, General Motors further expanded its illumination-aiding technology in 1960 with the 'Twilight Sentinel'. As the name suggests, this separate system would turn the car's lights on when the ambient light level dropped below a certain point.

At any rate, the Autronic-Eye alone paved the way for safer night driving, with many owners appreciating its automatic dipping and extended high beam use. It wasn't flawless, mind, suffering from occasionally erratic function - but it established the foundations for myriad future set-ups with the same intent.

'The end's in sight for the "headlight fight",' proudly stated the advertising material. 'No more duelling over who will do the dimming first!'

P.H. O'meter

Join the PH rating wars with your marks out of 10 for the article (Your ratings will be shown in your profile if you have one!)

  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10
Rate this article

Comments (26) Join the discussion on the forum

  • cmoose 19 Mar 2018

    Interesting. This was referred to obliquely in Mad Men. Don Draper's Caddy had it. I was wondering how it was done back then. I can't imagne it worked terribly well. Possibly just about visible in this image:



    These days, I think the problem of the apparently medicated driving along empty country roads on dipped beam is more of an issue than being blinded by oncomers. A quick taste of one's xenon's is usually enough to encourage another car to dip. But coming up behind somebody bimbling along on dipped beams presents a bit of an issue re overtakes!

  • Lewis Kingston 19 Mar 2018

    cmoose said:
    Interesting. This was referred to obliquely in Mad Men. Don Draper's Caddy had it. I was wondering how it was done back then.
    Incredibly well spotted – yes, that's the Guide-Matic assembly on the dash. Top stuff!

  • Usget 19 Mar 2018

    There's a fundamental design issue with these systems, including the modern ones.

    Since they wait until they've seen oncoming lights before dipping, by the time they've dipped, the oncoming driver has already been dazzled.

    Whilst I share the sentiment of the engineer from the article - to whit, that it's useless to expect people to behave courteously - I do feel that the increasing popularity of auto-dim lights is just leading to driver laziness.

  • PoopahScoopah 19 Mar 2018

    Usget said:
    Whilst I share the sentiment of the engineer from the article - to whit, that it's useless to expect people to behave courteously - I do feel that the increasing popularity of auto-dim lights is just leading to driver laziness.
    Yes. Nearly all automation encorages laziness amongst the part of the driving community that has no interest in driving.

    I admit I do like some modern features (cruise control for example) but these are just a convenience for when needed rather than something to rely on. I still actively take part in the driving for the most part. But too many people take the attitude of why should I bother checking or doing xyz now, when the car will do it for me? Classic case in point being people not switching their lights on at night because they have automatic DRLs, so they forget that they don't have their dipped beams (and possibly the tail lights) on.


  • Ares 19 Mar 2018

    PoopahScoopah said:
    Usget said:
    Whilst I share the sentiment of the engineer from the article - to whit, that it's useless to expect people to behave courteously - I do feel that the increasing popularity of auto-dim lights is just leading to driver laziness.
    Yes. Nearly all automation encorages laziness amongst the part of the driving community that has no interest in driving.

    I admit I do like some modern features (cruise control for example) but these are just a convenience for when needed rather than something to rely on. I still actively take part in the driving for the most part. But too many people take the attitude of why should I bother checking or doing xyz now, when the car will do it for me? Classic case in point being people not switching their lights on at night because they have automatic DRLs, so they forget that they don't have their dipped beams (and possibly the tail lights) on.
    "encorages [sic] laziness amongst the part of the driving community that has no interest in driving"

    Not sure I agree. My last three cars have had this, current car it is automatic, and I think it's a brilliant tool. Anything that keep more attention on driving is good in my book.

    As for only dipping headlights when you can see the lights coming the other way....Isn't that how eyes work? And the automatic reaction time is likely to be better than human?

    I'd not discount a car that didn't have them, but I think it's a great product.

View all comments in the forums Make a comment