Legal Question About Dry Vans And Marker Lights

Hello i recently left wilson to go work for us xpress as an OTR company driver. this seems like an ok job for my skill level (9 months otr reefer/dry van experience)

but something is confusing the hell out of me and need to know how to properly research this subject.

when i go to pickup a us xpress empty (all dry vans) usually the first thing i check in a pre trip is to make sure all the lights on the back of the trailer work.

i start with my 4 way flashers then hit the light test button in my cascadia and work back to front.

anyway i noticed that half the empties i inspect with us xpress dont even have marker lights on the top right/left of the back of the trailers.

with prime trailers i make sure those top corner lights on the back of the trailer are illuminated and can blink.

the folks at the shop at the us xpress terminal told me that if there are no lights mounted on the top left/right of the rear that not to worry about it...that its only the trailers they have with those corner lights mounted i should test.

does this sound right to you all? how do i double check this info?

im very consistant with my pre trips and dont want to get lazy with them lol

All installed lights need to work properly. Different types/year models of trailers have different light configurations.

Your only concern is the installed lights do work.