They've been standard for about a century, but recently I've been left wondering too many times.
I'm concerned by the number of people driving at dusk without switching on their headlights.
I've seen vehicles with no lights on - or rather I've only seen them belatedly - travelling on highways well past 5pm.
At this time of year, that's sunset.
The NSW road rules state headlights must be on between sunset and sunrise, and "at any other time where there's not enough daylight to see a person wearing dark clothing at a distance of 100m".
It's not a new issue.
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A 2013 NRMA Insurance study found that 14 per cent of motorists driving after sunset did not have their car headlights on, "increasing the risk of a collision".
Unfortunately, in my experience, there remains a portion of drivers continuing to do this.
When highlighting the issue eight years ago, the NRMA, citing its own claims data, reported the daily average number of motor collisions doubled between 3pm and 6pm and the risk increased with low visibility.
More than 1500 vehicles were filmed on a busy Sydney arterial road during peak hour in low light, showing more than one in ten without their lights on, the study showed.
I'm particularly concerned the lights aren't always being turned on on rural and regional roads.
I really don't understand why motorists wouldn't want to turn their lights on - and be as visible as possible - as the sun starts to sink towards the horizon.
I'm not talking about dazzling other drivers with high beam - that's not permitted either.
So this is a reminder to turn on your headlights at the appropriate times of the day, or when the conditions require it, and make the roads safer for everyone.
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