[DasBoot]

Along with just about anything else you say/do, there are several laws against this in Calif:

Upper and Lower Beam
24407. Multiple-beam road lighting equipment shall be designed and aimed as follows:

(a) There shall be an uppermost distribution of light, or composite beam, so aimed and of such intensity as to reveal persons and vehicles at a distance of at least 350 feet ahead for all conditions of loading.

(b) There shall be a lowermost distribution of light, or composite beam so aimed and of sufficient intensity to reveal a person or vehicle at a distance of at least 100 feet ahead. On a straight level road under any condition of loading none of the high intensity portion of the beam shall be directed to strike the eyes of an approaching driver.

Flashing Lights
25250. Flashing lights are prohibited on vehicles except as otherwise permitted.



Permitted Flashing Lights
25251. (a) Flashing lights are permitted on vehicles as follows:

(1) To indicate an intention to turn or move to the right or left upon a roadway, turn signal lamps and turn signal exterior pilot indicator lamps and side lamps permitted under Section 25106 may be flashed on the side of a vehicle toward which the turn or movement is to be made.

(2) When disabled or parked off the roadway but within 10 feet of the roadway, or when approaching, stopped at, or departing from, a railroad grade crossing, turn signal lamps may be flashed as warning lights if the front turn signal lamps at each side are being flashed simultaneously and the rear turn signal lamps at each side are being flashed simultaneously.

(3) To warn other motorists of accidents or hazards on a roadway, turn signal lamps may be flashed as warning lights while the vehicle is approaching, overtaking, or passing the accident or hazard on the roadway if the front turn signal lamps at each side are being flashed simultaneously and the rear turn signal lamps at each side are being flashed simultaneously.

(4) For use on authorized emergency vehicles.

(5) To warn other motorists of a funeral procession, turn signal lamps may be flashed as warning lights on all vehicles actually engaged in a funeral procession, if the front turn signal lamps at each side are being flashed simultaneously and the rear turn signal lamps at each side are being flashed simultaneously.

(b) Turn signal lamps shall be flashed as warning lights whenever a vehicle is disabled upon the roadway and the vehicle is equipped with a device to automatically activate the front turn signal lamps at each side to flash simultaneously and the rear turn signal lamps at each side to flash simultaneously, if the device and the turn signal lamps were not rendered inoperative by the event which caused the vehicle to be disabled.

(c) Side lamps permitted under Section 25106 and used in conjunction with turn signal lamps may be flashed with the turn signal lamps as part of the warning light system, as provided in paragraphs (2) and (3) of subdivision (a).

(d) Required or permitted lamps on a trailer or semitrailer may flash when the trailer or semitrailer has broken away from the towing vehicle and the connection between the vehicles is broken.

(e) Hazard warning lights, as permitted by paragraphs (2) and (3) of subdivision (a) may be flashed in a repeating series of short and long flashes when the driver is in need of help.

24409. Whenever a motor vehicle is being operated during darkness,
the driver shall use a distribution of light, or composite beam,
directed high enough and of sufficient intensity to reveal persons
and vehicles at a safe distance in advance of the vehicle, subject to
the following requirements and limitations:
(a) Whenever the driver of a vehicle approaches an oncoming
vehicle within 500 feet, he shall use a distribution of light or
composite beam so aimed that the glaring rays are not projected into
the eyes of the oncoming driver.
The lowermost distribution of light specified in this article
shall be deemed to avoid glare at all times regardless of road
contour.
(b) Whenever the driver of a vehicle follows another vehicle
within 300 feet to the rear, he shall use the lowermost distribution
of light specified in this article.