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Honor the Fallen
Are they teaching what those lights mean in driver's education classes? If not, what good are they for 90% of the driving population? I'm 43, have been driving for 28 years, and never knew what they were for.
HA I'm answering my own question
Clearance lights are required on a vehicle if it is 8' wide. The DRW trucks must have them on the cab AND also on the rear of the vehicle because their axle width is 8' wide.
Before they became a vehicle option on pickup trucks, trailer manufacturers put them on both the front and rear corners of trailers, some even put the gang-3 on the front but all had them on the rear.
More often than not, a 1-ton SRW pickup will come with them on the cab because is is 'assumed' that someone buying a 1-ton truck tows trailers that are 8' wide. Many trailer manufacturers stopped putting the gang-3 lights on the front of their trailers, cost-cutting manufacturing overhead, because the 1-ton trucks had the clearance lights up front. The law stipulates that the lights must be on the front and rear of vehicles/trailers 9' wide. So, the clearance lights on the cab and the clearance lights kind of accommodated the 8' wide package from front to rear of the combined vehicle/trailer. Jim Lane is correct - the 3 inside are ICC and the two outside are designated clearance. If you tow an 8' wide trailer that does not have front clearance lights, either install them on your trailer or install the two outside on your truck's cab. Then you will be legal according to DOT law.