Warning lights on channelizing devices
In Pennsylvania, Type A and C lights on drums may be used at the TCP designer’s discretion, but there is no requirement to use them. Type A lights may not be used if the distance between the lights is less than 250 feet, and in this case they use Type C lights. Type C lights are used when a series of lights are specified.
Type A and C lights are not normally used on Type III barricades. (Type B is used instead.)
Type A and C lights are used on temporary warning signs only when needed to call special attention to the message.