What is the proper statutory interpretation of 26 U.S.C. § 7701(a)(48)(A)(i) regarding the classification and taxation of specialized vehicles?

This statutory interpretation case raises the primary question as to the plain (best) meaning of 26 U.S.C. § 7701(a)(48)(A)(i) and, in the context of the federal excise tax scheme under 26 U.S.C. § 4051(a) , raises these four interrelated issues regarding the test for applying that statutory exception : 1) What role does the ability of a vehicle to transport a load over the highway play in the statutory inquiry under 26 U.S.C. § 7701(a)(48)(A)(i) ? 2) Does the two-prong test under 26 U.S.C. § 7701(a)(48)(A)(i) require comparison of the vehicle in question to a traditional highway vehicle to identify the special design features and impairments or limitations ? 3) Whether the phrase “specially designed for the primary function of transporting a particular type of load other than over the public highway…” as used in 26 U.S.C. § 7701(a)(48)(A)(i) require s consideration of the design elements of the entire vehicle or just particular components of the vehicle ? 4) Does the phrase “substantially limited or impaired” as used in 26 U.S.C. § 7701( a)(48)(A)(i) require consideration of all forms of impairment or limitation ? -iiRULE 14( b) STATEMENT The