The effectiveness of the granular sub-base (GSB) layer in a pavement system extends beyond its structural role to include essential drainage functions. In India, current guidelines recommend using natural sand, crushed gravel, stone, or slag, either individually or in combination, to construct GSB layers. While these materials meet structural requirements, their ability to comply with drainage standards (a minimum of 300 m/day as per IS standards) remains uncertain. This paper presents laboratory tests assessing the permeability of GSB materials and their combinations with geo-drains. The study focuses on GSB of gradation V, as per MoRTH specifications (5th Revision), and compares the drainage characteristics of standalone GSB with GSB–geotextile/geo-drain combinations. Both horizontal and vertical permeability tests were conducted on the materials, considering various hydraulic gradients and geo-drain placement depths. The results demonstrated that combining GSB with geotextiles and geo-drains significantly improved permittivity and transmissivity. Permittivity increased by 1.70 times with non-woven geotextiles (NWG), 2.70 times with 2D geo-drains, and 3.60 times with 3D geo-drains at a hydraulic gradient of 1. Transmissivity improved by approximately 5 times for NWG, 7 times for 2D geo-drains, and 12.5 times for 3D geo-drains at a hydraulic gradient of 0.1. This study demonstrates the benefits of incorporating geo-drains with granular sub-base (GSB) layers to improve drainage in pavement systems, thereby extending pavement life and maintaining high performance, even in areas heavily impacted by water.