What is DRL (Daytime Running Lights)?
What does DRL mean?
Daytime running lights. If a vehicle has DRL, the main intension is that as long as the engine is running, lights will come on automatically.
Where is DRL usage mandatory?
Canada and forty other countries under ECE regulations. Not required in the US, which means that some vehicles has and some don’t, which worsens the safety standpoint. ECE regulations also require parking and tail lights to be operational. Canada has not adapted that portion.
What are the pros of DRL usage?
Studies showing that collision rates decreases.
Oncoming traffic will see you better.
What are the cons of DRL usage?
Masking. Bright driving lights with the same color as daylight will make your a car invisible viewed against a sunrise/sunset or during an overcast day (very high Kelvin ambient light). Another example of masking is one dark car in a row of many with DRL.
What about HID Kits and DRL?
Oncoming traffic will see you even better when they sparkle in all sorts of colors, and it defiantly looks “cooler” than orange halogen on “half speed”.
However when installing an HID Kit it is always recommend to disable your Daytime Running Lights. Technically, a resistor could be placed in series with a bulb to lower voltage and therefor output, but it would not be possible to go below a certain voltage. Below around 10Volts, bulb does not get hot enough and start making inside of bulb glass smoked, which of course is not good. The most common solution to this is to send squared waved pulses with a wave length of about 12ms of 12V hight. By varying the time off in comparison to time on, the desired output can be achieved. As an example, if you have a 55W bulb, and have 1:1 relationship, it would give half the output. In most realistic cases, square wave is more on than off, giving out 60-80% of full wattage.
How does high beam DRL systems with lower intensity work?
Low beam DRL systems are not very common in North America, however, it is perfectly legal. High beam DRL systems are very common. The main reason for using high beam is simply a marketing/safety/reliability thing from manufacturer. Since full power high beams in general are used 30% and low beams are used 70%, automaker can make bulbs last longer by combining high beam with DRL function.
[Source]