Rear position lamps (tail lamps)

Night time vehicle conspicuity to the rear is provided by "rear position lamps" (also called "taillamps" or "tail lamps", "taillights" or "tail lights"). These are required to produce only red light, and to be wired such that they are lit whenever the front position lamps are illuminated—including when the headlamps are on. Rear position lamps may be combined with the vehicle's stop lamps, or separate from them. In combined-function installations, the lamps produce brighter red light for the stop lamp function, and dimmer red light for the rear position lamp function. The tail and stop light functions may be produced separately or by a dual-intensity lamp.
Regulations worldwide stipulate minimum intensity ratios between the bright (stop) and dim (tail) modes, so that a vehicle displaying rear position lamps will not be mistakenly interpreted as showing stop lamps, and vice versa.
Many modern designs use LED lighting sources beginning in 1999 with the 2000 Cadillac Deville
Stop lamps (brake lights)

Red steady-burning rear lights, brighter than the rear position lamps, are activated when the driver applies the vehicle's brakes. These are called "stop lamps", or, colloquially, "brake lights". They are required to be fitted in multiples of two, symmetrically at the left and right edges of the rear of every vehicle. Outside North America, the range of acceptable intensity for a stop lamp is 60 to 185 candela.In North America, the acceptable range for a single-compartment stop lamp is 80 to 300 candela