On-road object detection is a critical component in an autonomous driving system. The safety of the vehicle can only be as good as the reliability of the on-road object detection system. Thus, developing a fast and robust object detection algorithm has been the primary goal of many automotive industries and institutes. In recent years, multi-purpose vision-based driver assistance systems have gained popularity with the emergence of a deep neural network. A monocular camera has been developed to locate an object in the image plane and estimate the distance of the said object in the real world or the vehicle plane. In this work, we present a monocular 3D object detection method that utilizes the discrete depth and orientation representation. Our proposed method strives to predict object locations on 3D space utilizing keypoint detection on the object’s center point. To improve the point detection, we employ center regression on the objects segmentation mask, reducing the detection offset significantly. The simplicity of our proposed network architecture and its one-stage approach allows our algorithm to achieve competitive speed compared with prior methods. Our proposed method is able to achieve 26.93% detection score on the Cityscapes 3D object detection dataset, outperforming the preceding monocular method by a margin of 2.8 points.