The CDL General Knowledge test is not quite the same thing as the CDL permit test, as an applicant is required to pass all the various relevant written knowledge tests in order to obtain a commercial driver's license and permit. Different knowledge tests are required depending on the class of CDL permit for which the driver applies.
Class A, B and C commercial driver's licenses all require the applicant to pass the General Commercial knowledge test, while both Class A and B also require the airbrake knowledge test. There are also a number of special endorsements for which a driver can apply, alongside the different classes, such as school bus, passenger transport, hazardous materials and tanker endorsements. Each endorsement requires the applicant to pass a general knowledge test directly related to that specific area.
After passing the General Knowledge tests and obtaining the CDL permit, the person is then allowed to practice driving under limited circumstances, in order to prepare for the CDL Road Test, which can be taken 30 days after the permit was issued. To take the road test, it is necessary to bring along both the appropriate vehicle for the desired class of license and a licensed driver who is at least 21 years old and possesses the same class of CDL license.