Adding driving lights to E-450 (UPDATE)

Gdetrailer wrote:
DRLs typically used either the headlights (low beams) at a reduced voltage (does not burn at full brightness) or a separate low brightness powered, which MUST AUTOMATICALLY turn on anytime the vehicle is running.

Gdetrailer's info is generally right on.

I just wanted to add that, while some vehicles do use the low beams (either at low power or very occasionally at full power), it's also common--I think perhaps more common--to use the high beam lights at reduced power for the DRLs. Certainly that's been the design used on the cars I've had with DRLs.

The high beams have a couple of advantages here: they aren't designed with a cutoff generally below the eye level of oncoming drivers, so they're more visible, and typically people use the low beams more than the high beams on headlights so the low beams tend to burn out more quickly. Using the high beams for DRLs thus doesn't impact the life of the headlight bulbs as much, particularly when it's a single dual-filament bulb and both low and high must be replaced simultaneously. (I'm talking about incandescent bulbs here, of course, and not newer technologies such as LEDs or HIDs.)

I think a few vehicles used the parking lights, too.