त्रयः प्राचीना राजमार्गास्त्रय उदीचीना इति वास्तुविभागः ॥ कZ_०२.४.०१ ॥
trayaḥ prācīnā rājamārgās traya udīcīnā iti vāstuvibhāgaḥ
The town-plan division is: three royal highways running eastward and three running northward.
A fixed arterial grid simplifies policing, taxation movement, military mobilization, and maintenance budgeting by making circulation predictable and inspectable.
They are state-priority corridors for administration, trade supervision, and rapid troop/police movement—hence centrally planned and regulated.