This structure, being part of the larger NZASM endeavour, falls under the generic NZASM statement of significance, but specifically is also a good extant example of its type. Its importance lies in its associations with South Africa's community, heritage, and is considered uncommon, rare and endangered; it has the potential to yield information for understanding; as an object it demonstrates principal characteristics; has particular aesthetic characteristics; demonstrates a high degree of technical achievement; has strong and special associations with both historic and contemporaneous communities; has a special association with the life and work of an important organisation and its associated persons; and is significant in revealing labour practices of the time; all as they relate to the culture of South Africa and her international cultural historic affiliates. It is a unique structure in that it was designed at a curvature and an incline to accommodate the ratchet line system. (Government Gazette 1516 of 1962: 'The tunnel was part of the N.Z.A.S.M railway line built in 1891-1895 between Pretoria and Lorenco Marques. In few of the steep gradient it was fitted with a rack railway.)
