What Are Daytime Running Lights and Why Do I Need Them?

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Daytime running lights help keep you safe, but there are a few things to know about this lighting system.

Have you ever been driving at dusk, in the rain, or after dark and seen a car go by without its headlights on? Maybe it was a black car and you noticed it at the last second. Ideally, cars would have a system that always turned the headlights on when needed, but for a variety of reasons, including cost, automakers don’t make headlights automatic in all cars. Even those vehicles that do have the feature usually have a way to disable it and go to an on/off function controlled by the driver. Daytime running lights (or DRLs) help with this problem of having completely dark cars being operated in low light conditions and are also intended to help in other circumstances.

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DRLs were originally made popular in parts of the world where daylight can often be dim and short in duration. They work great as a way to identify the car using them to other cars on the road. Unlike headlights, they are not intended to illuminate the road ahead, and they don’t also have any rear marker lights. They are simply dim lights at the front of the vehicle.

In vehicles equipped with daytime running lights or DRLs, the system is automatic. They are intended to be on when the vehicle is driven without requiring any driver input. The way they work varies from automaker to automaker, and even from model to model. In nearly all the systems originally developed, they worked by using a lower power setting on already existing lights, typically the high beams. As time went on, many automakers have adopted DRLs as a sort of jewelry or brand identifier and LED bulbs are now popular.

Once enabled, DRLs are completely automatic and work without any need for driver involvement. They are usually on when the car is on, but some automakers, Subaru for example, enable them only when the vehicle is in a gear other than “Park.” When the headlights are turned on by the driver or the automatic system the vehicle is equipped with, the DRLs may stay on or turn off. Once the headlights are enabled they are no longer needed, except again, as a way to make the car look distinctive.

DRLs are pretty simple to understand and the reasons why they are used are hard to argue against. Yet some do. In fact, there are anti-DRL groups who lobby against them.¬† The main argument put forth is that they are not “effective.” Or not “necessary.” We won’t weigh in on the subject, but if there is some harm in having DRLs it is hard to understand what it might be. Canada has mandated all new cars have DRLs since 1989 and has fines for drivers not using them.

 

In some vehicles equipped with DRLs, the system can be disabled, perhaps to satisfy the naysayers, or perhaps for those who want to operate in stealth mode. If your vehicle’s DRLs are not working for some reason, or if just one is, the typical cause is a bulb having burned out. In many cars, the bulb is shared with another function, so try the other lights to see if you can identify the cause. Before you go too far into the troubleshooting process, we suggest a quick glance at the owner’s manual. They may just be in the off position or not enabled in the scenario you expect.

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John Goreham

John Goreham