(a) A separate vehicle configuration shall be determined by each combination of the following parameters:

(1) Exhaust system configuration.

(i) Single vertical.

(ii) Dual vertical.

(iii) Single horizontal.

(iv) Dual horizontal.

(2) Air induction system (engine). (i) Natural.

(ii) Turbocharged.

(3) Fan.

(i) Diameter.

(ii) Drive.

(a) Direct.

(b) Thermostatic.

(iii) Max fan rpm.

(4) Engine manufacturer's horsepower rating.

(5) Cab characteristic.

(i) Sleeper.

(ii) Non sleeper.

(6) Category parameters listed in §205.55-2.