From gas lamps to LEDs: The 100-year war on headlight glare

The brightness of modern headlights is the subject of a major inquiry, after a swell of public opinion exemplified by this letter to Autocar: "As regards dazzle, the [main] beam is as great a source of danger as the side [beams], and I certainly think that all high-powered lamps should be provided with some anti-dazzle arrangement as standard. Powerful headlights of the sort are a positive nuisance, not to mention danger." Of course, this news comes to you from 1912, when the average new car headlight brightness achieved 21 candlepower. That's roughly 13 times dimmer than the average today and it was the soft orange glow of acetylene gas, as opposed to the bluish white blaze of LEDs. Seriously, a time-travelling SUV would make any Edwardian driver think Judgment Day were dawning behind him. In fact, the issue of dazzle had already been raised in parliament back in 1908, the Liberal MP for Kincardineshire claiming it had caused accidents to both drivers and cyclists and asking what could be done to prevent it. The government replied that an "appropriate method of dealing with the matter" had yet to been found. Enjoy full access to the complete Autocar archive at the magazineshop.com The problem was brought up by MPs periodically in the years following, even after Autocar suggested in 1930 that it had been solved by the advent of the "dip-and-switch device" - a button or plunger that caused a mirror to swivel over the left light, thus deflecting its beam downward, while switching off the right light. Many other anti-dazzle devices were appearing at the time, among them shields, reflectors, shutters, dual filaments and special cells between bulb and lens. In fact, 85 were submitted to the RAC for evaluation in 1931. Public interest in the subject was enormous, too: at the test evening in Cambridge, it became "practically impossible to demonstrate the efficiency of the devices, as they encroached on the fairway to such an extent that the dummy cyclists set up as a part of the test were lost in the crowd". Two years on, we received news from France that "the authorities are going to insist upon all motor car headlamps throwing a yellow beam. This will, it is thought, be a safer light in various ways and less tiring to a driver's eyes." Many wondered if Britain should follow suit, but domestic industry leader Lucas believed that "neither for driving in fog nor for reducing dazzle, and at the same time retaining a good driving light, is any advantage to be gained from the use of a coloured filter". No tint for us, then, but dipping reflectors quickly became popular additions to cars in Britain. "In spite of this," though, a reader wrote to complain in 1935, "the nuisance of dazzle still persists, and there seems to be a vast number of cars on the road with no control to the nearside headlight; the offside headlight is switched off, and presumably one is expected not to be dazzled by the other." It must have come as a great relief to them when the long-delayed Road Vehicles Lighting Regulations finally appeared in 1936, containing a requirement of new cars that "unless a headlamp is focused so as not to cause dazzle at an eye level of 3ft 6in a distance of 25ft from the lamp on the same plane, then the driver must be capable of deflecting the beams, or switching over to other lamps, etc, so that dazzle is not caused." In October 1937, these regulations were extended to cover "every lamp the light of which is derived from an electric bulb carried on any vehicle". All motorists thus needed to install aftermarket anti-dazzle measures - although this was an easier task than you might assume, because in those days lights weren't integrated into vehicles' bodies to anything like the extent that we're used to. In advance, we printed a helpful feature detailing various compliant aftermarket lights, costing between about £1 and £4 (the equivalent of £60 to £240 in modern money). The penalty for non-compliance was a £5 fine initially and a £20 fine for a repeat offence - but it would seem that wasn't punitive enough, because in 1939 an MP was moved to asked for greater publicity of the regulations and the government "agreed that drivers need to be reminded of their obligations". Dipped beams for all eventually did greatly improve the experience of driving in the dark, though. Let's hope the government's ongoing inquiry into the glare of LEDs will result in something similar.

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From gas lamps to LEDs: The 100-year war on headlight glare

Solving the problem of headlight dazzle took a long time the first time round; will it be quicker now?

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From gas lamps to LEDs: The 100-year war on headlight glare

Solving the problem of headlight dazzle took a long time the first time round; will it be quicker now?

More from Autocar

Top 10s

Latest car reviews

Top manufacturers

Quick search

We recommend

Legal bits

About Autocar