Traditional image processing methods used for detecting traffic lights and traffic signs are replaced by the recent enhancements of the deep learning method by the success of building a Convolutional Neural Network (CNN). In this research, a traffic lights and traffic signs detection system using a modified You Only Look Once (YOLO) has been proposed. The system processes an image captured by a camera sensor and provides the results in the form of detecting traffic lights and traffic signs contained in the image. The CNN architecture used is a modified Cross Stage Partial YOLOv4 (YOLOv4-CSP). The experiments were carried out using a self-constructed dataset consisting of1360 training data and 340 testing data with 6 types of traffic lights and 39 types of traffic signs. The network is built using the Darknet framework and the result shows 79,77% of the mean Average Precision at the 0,5 Intersection over Union threshold (mAP at 0,5 IoU threshold) and 29 frames per second (FPS) of inference speed tested on a single NVIDIA Tesla T4 Graphics Processing Unit (GPU).