Autonomous driving is the main application of Internet of Things (IoT) technology in the field of intelligent transportation. In autonomous driving, self-driving cars will avoid changing lanes in a short distance. When the self-driving car executes the follow-up instruction, the road smoothness in front of the car will affect the driving safety and comfort of the car. The real-time acquisition of road information in front of driving will help the self-driving car adjust driving behavior. However, other vehicles on the road will lead to the failure of Light Detection And Ranging (LiDAR) detectors to obtain complete road point cloud data. The incomplete road point cloud data need to be imputated to avoid potential misjudgements of the road conditions. Currently, little research work specifically focuses on imputating the incomplete road point cloud data that are caused by obstacle vehicles. In this paper, we propose a fast method to imputate the incomplete road point cloud data using a Graphics Processing Unit (GPU)-based parallel Inverse Distance Weighted (IDW) interpolation algorithm to enhance the safety of autonomous driving. To evaluate the performance of the proposed method, two groups of experiments are conducted. The experimental results indicate the following: (1) the known point cloud data within 5 meters around the obstacle vehicle are sufficient to guarantee the imputation accuracy; (2) when the weight parameter of the IDW interpolation is 4, the efficiency and accuracy of the imputation can be optimally balanced; and (3) it takes approximately 0.6 seconds to imputate the incomplete dataset consisting of 15 million points, while the imputation error is approximately 5 millimeters. The proposed method is capable of efficiently and effectively imputating the incomplete road point cloud data that are induced by obstacle vehicles and outperforms other interpolation algorithms and machine learning algorithms. INDEX TERMS IoT, self-driving car, path planning, data imputation, interpolation algorithm, GPU.