Roadway drainage is designed to collect the stormwater and channel it to a proper drainge system such as the stormwater inlets to avoid flooding on the road. A common type of stormwater inlet is the curb-opening inlet. The efficiency of the curb-opening inlets remains as one of the major challenges that causes surface ponding on the pavements and disturb the traffic movement. This paper aims to assess the efficiency of a typical depressed curb-opening inlets used in Malaysia through experimental, numerical, and field investigations. The experiments were conducted for various flows in a fabricated full-scale halfway road model. Later, a three-dimensional (3D) numerical modelling was developed using FLOW-3D software to validate outcomes from the experiments. Furthermore, a field investigation was also conducted at a selected area within the university to further compare the results. Outcomes from these three approaches showed similar trend, whereby the efficiency of depressed curb-opening inlet decreases as the approaching flow increases. On the other hand, some difference was observed between the experimental and field results. This could have caused by the surface roughness of the actual road, which would have infiltrated into the ground, leaving less flows to be intercepted by the inlet. © 2024, Institute of Technology PETRONAS Sdn Bhd.