It is advisable to have your lights on at all times because studies show that vehicles driven with lights on at all times are much less likely to be involved in collisions than those operated with their lights on at night only.
The law requires the use of headlights from half an hour after sunset until half an hour before sunrise, and at any time when visibility is poor.
Note: Some vehicles do not have tail lamps on when daytime running lights are being used.
When meeting another vehicle, you must dim your headlights at least 200 m (650 ft.) in advance of oncoming vehicles and keep them dimmed until the vehicle has passed.
Many drivers make the error of dimming their headlights too soon for oncoming vehicles. For example, when driving at 100 km/h, you may not have to dim your high beams until the approaching vehicle is about eight to seven seconds away from you, but a realistic approach is to dim your lights between nine and 12 seconds away.
While you need to see the road, you should not blind the oncoming driver with the glare of your lights. You may find that some drivers approaching you will signal you to lower your lights while they are up to 20 seconds away. This applies to vehicles you are meeting and vehicles you are following. To avoid blinding other drivers, make sure your headlights are properly adjusted and are in working order.
Also, turn off any spotlamps at least 500 m (1,640 ft.) in advance of an oncoming vehicle and keep them turned off until the vehicle has passed.
You are not required to dim your headlights for oncoming traffic if you are driving on a divided highway where the distance between the roadways is 22 m (70 ft.) or more (the distance is measured from left shoulder marking to left shoulder marking in each direction of travel).
You must keep your headlights on low beam within 100 m (330 ft.) and keep any spotlamps or auxiliary driving lights turned off within 500 m (1,640 ft.) when you are following another vehicle, or when you are being passed.
If you have been driving in the dark for a while, you will need up to five seconds to recover from the glare of oncoming lights. This glare recovery time tends to increase with age to the point where it sometimes takes up to 25 seconds to recover. If you suspect you have a glare recovery problem, check with an ophthalmologist or optometrist.