Question:
I'm preparing to take the written exam for my CDL. The manual says the following lights must be clean and working properly:
reflectors
marker lights
clearance lights
taillights
identification lights
I know what taillights are but what are the rest and where are they located?
thanks

Answer:
The really short answer: If it is a light and it is on the truck then it had better be in working order.
Reflectors can be found about anywhere on the truck or trailer. Some of the more common places are on the rear of the truck or trailer near the tail lights, on the side of the trailer (more often than not it is reflective tape now a days).
Clearence lights are the ones that are on top of your tractor and trailer in the front of each unit. There are 5 on the tractor and at least 2 (on each front corner) of the trailer.
Identification lights: Sometimes called tag lights (lisc plate lights) . Also sometimes the 3 small lights on the rear of the trailer are called this too.
Marker lights (pretty much what ever is left over) The lights on the sides of the truck and/or trailer , and on the rear corners of the trailer.
You also need to make sure that all turn signal lights are in working order., and not excessivley dirty.
I may be off a bit on the names of each lights but the locations are valid at any rate.