Why don't manufacturers dispense with daytime running lights altogether and simply have the full lighting system, front and rear, come on whenever the car is running. This would save them money since they wouldn't have two separate systems and they could implement that approach worldwide, rather than having different systems in different jurisdictions depending on the regulatory requirements.
Presumably the full lighting system would satisfy those requirements wherever they exist. It would also eliminate all of the issues about rear lights not being on in low-visibility situations like fog or the need in some places to have lights on when the wiper blades are activated. The only downside I can think of is that the light bulbs may burn out sooner from the extended use, but that is a relatively minor annoyance and cost and is less of an issue with halogen and LED lights now used in many cars. – Carl
Nice try – but the answer lies in that mention of "different jurisdictions."
Lighting regulations are among the most arcane in the automotive world. There are places where it is illegal to have your lights on during the day. In others, you can't use your emergency flashers in a moving vehicle, still others dictate the power and type of bulb to be used as well as the colour and aim of the light stream.
Daytime Running Lights are a perfect example – proven to save lives, yet because American consumers don't like them, they are not mandatory and we have to jury-rig the vehicle sold here but built for there.
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