this was cut from a lighting forum. i hope i don't upset the writer.originally think it was dan stern.
*What are "city lights" ?
E-code lamps sometimes include a City light.(These are called "side lights" by speakers of British English. This can be a bit confusing, because they face *front*, not to the side.) What is a city light? It's a 5-watt lamp that sticks through the lamp's reflector into the lamp itself. European vehicles are equipped with city lights rather than US-style amber parking lamps. City lights are legal for use as parking lamps in the US and in Canada; amber parking lamps are NOT mandatory.
*How would I make the city light work on my car? The DOT headlamps I'm replacing didn't have them.
The city light has two wires. Ground one of its wires, and run the other of its wires to the dim filament feed on your front park lamps, preferably instead of (but optionally in addition to) your existing dim amber park lamp filaments. This makes for parking lamps that WORK, and if a headlamp ever malfunctions, oncoming traffic still sees you as a double-track vehicle. In addition, it makes your front turn signals much clearer because they now go "BRIGHT-off-BRIGHT-off" instead of "bright-dim-bright-dim" when the lights are on. Yep, another aspect of lighting that the Europeans got right and we didn't. City lights are especially useful if you have fog lamps. On foggy days, you can put on the city lights which will show other drivers exactly where u have fog lamps. On foggy days, you can put on the city lights which will show other drivers exactly where your car is, and switch on the fog lamps so you can see.
http://www.endosquid.com/audi/audinfo_lightFAQ.htm#
peter