Angkor's Roads: an Archaeo-Lexical Approach

"The aggregation of power by the Angkorian Empire required improved communication and diversity in the transport system. We see in the Khmer texts an increase in the frequency and diversity of transport terminology, particularly in the 11th century when the Khmer expanded rapidly across the region. This includes a shift in focus from thnal to phlu and the introduction of Sanskrit terms for roads into the Khmer language texts, coincident with a shift to more formalized roads. Overall, the inscriptions do support the view that the Khmer road system was well-established before the reign of Jayavarman VII.

"Previously, the only definite association of a road term with a main road was with the Sanskrit adhvan. Yet, rathyā and mārga and possibly patha may also have been used, as they are found in proximity to the Northwest and West roads. In Khmer language texts, it is suggested that an expression for state-built roads, such as the Northeast Road and possibly the sacred “triple way” created by the Siem Reap diversion, was vraḥ phlu. Vraḥ thnal, however, appear to have been more localized temple causeways".