Commercial Drivers License
In order to obtain your Commercial Drivers License
(CDL), a student driver will demonstrate a proficient
understanding of the air brake system in both a written
exam and an oral exam at the Department of Motor
Vehicles (DMV). This written exam will be taken along
three other written tests when obtaining a Commercial
Learners Permit (CLP), and the oral exam will be
conducted on the day of the student driver's road test.
Remember, per
Federal Motor Carrier Safety Regulations
(FMCSR), a student driver must hold their CLP for a
minimum of 14 days prior to taking the skills test, or
commonly referred to as the road exam, at the DMV.
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The DMV uses the COLAS acronym to identify each air-brake inspection test a student driver must
perform: Governor
Cut-In Test (C), Governor Cut-Out Test (O), Low Air Warning Test (L), Applied
Leakage Test (A),
Spring Pop-Out Test (S). The tests are not difficult in nature; however, they must
be performed with absolute accuracy, adding an additional level of difficulty to this portion of the
exam. It should also be noted that a student driver does not have to perform the tests in the COLAS
order. Most truck driving schools are equipped with the necessary tools/aids to help a student driver
learn and perform the five (5) DMV required air brake tests.
Did you know?
According to the FMCSR,
there are ten (10) air-brake
tests a driver should
perform when inspecting
their air brake equipped
commercial motor vehicle
Beyond learning the COLAS tests, a driver should also become familiar with how the air brake system
functions. A driver should become familiar with the physical aspects of the input and output side of
the air brake system. When taking our
CDLPro℠ Truck-Driver Training Program, students learn the
working details of the air system, allowing them a better understanding of why each air brake
inspection test is performed. For example, most students understand how to perform the Applied
Leakage Test, but fail to comprehend what is actually being tested (the physical part of the air brake
system). Although this information is not required, it is an expected level of knowledge motor carrier
(trucking) companies expect from their commercial drivers. Remember, some of what the DMV
requests in their CDL exam(s) is only basic information a driver must know, which implies that there
is more knowledge and information a driver should learn beyond DMV basics; and therefore,
becoming a professional entry-level truck-driver.
Here is a sample lesson from our air brake systems class discussing the air
compressor and its function in a commercial motor vehicle's air brake system.