For motor vehicles and trailers, two red tail lamps operate when the headlight switch is in the park position and the headlight position. The two lights are located close to the widest points of the vehicle so that the vehicle width can be seen by other road users.
The bulbs are connected in parallel to each other so that the failure of one filament will not cause total circuit failure. A number plate illumination lamp is usually connected in parallel to the tail lights and operates whenever the tail lights are on.
Tail lights are usually incorporated in a cluster assembly at the rear of the vehicle. Government regulations control the height of the lamps and their brightness.
The park lights, sometimes called clearance lamps, are located at the front of the vehicle and are used at night time when the vehicle is parked on the side of the road. They use low wattage bulbs and may have a lens or diffuser that makes the emitted light wide spread. In some cases, the park lights are incorporated in the headlight assembly.
The park lights operate when the light switch is moved to the first position. For safety reasons the park and tail lights continue to operate when the light switch is moved to the headlight position. The bulbs are connected in parallel with each other.
The circuit for the park and tail lights includes:
When the park light switch is closed current flows from the battery, through the fusible link to the park light switch, where it is fed through the fuse to the front park lights and to the rear tail and number plate lights.
After passing through the filaments the current path is completed through the frame of the vehicle to the negative battery terminal.
