8701.21.00 - With only compression-ignition internal combustion piston engine (diesel or semi-diesel)

This HTS category, 8701.21.00, specifically classifies road tractors designed for use with semi-trailers that are powered *exclusively* by a compression-ignition internal combustion piston engine, commonly known as a diesel or semi-diesel engine. These vehicles are the primary engine unit intended to pull a semi-trailer, forming a tractor-trailer combination for road transport. The defining characteristic here is the sole reliance on a diesel or semi-diesel engine for propulsion.

It is crucial to distinguish this category from its siblings based on the propulsion system. HTS 8701.22.00 covers tractors with *both* a diesel/semi-diesel engine and an electric motor for propulsion, indicating a hybrid system. HTS 8701.23.00 differentiates itself by specifying a spark-ignition internal combustion engine (gasoline) *combined with* an electric motor. For vehicles propelled *solely* by an electric motor, HTS 8701.24.00 would apply, while HTS 8701.29.00 serves as a residual category for other road tractors not meeting the specific criteria of the preceding subheadings.

Within this classification, a further distinction is made for the condition of the vehicle. The main subheading 8701.21.00 encompasses new road tractors fitting the description. A specific sub-subheading, 8701.21.00.80, exists to classify *used* road tractors that are powered solely by a compression-ignition internal combustion piston engine, allowing for separate statistical tracking based on the vehicle's prior use.