The monitoring of an accurate speed is crucial for driving safety, traffic efficiency, and environmental protection. However, the existing commercial wheel speed sensors require external power and costly maintenance. Triboelectric nanogenerators (TENGs) offer significant advantages for self-powered sensing due to their sensitivity to environmental changes. Therefore, the present study has introduced a planetary gear structure that is known for its efficient transmission and smooth operation characteristics. A planetary gear-driven triboelectric speed sensor (PGTS) has also been designed. The structural optimization was performed by combining finite element analysis with experimental results. At a speed of 120 rpm, the open-circuit voltage and short-circuit current could reach 10 V and 0.2 μA, respectively. Also, a peak power of 1.51 μW was achieved at a load resistance of 30 MΩ. A high-precision revolution speed sensing algorithm was further developed for a real-time and accurate perception of the vehicle speed. The research results demonstrated that the PTGS was successfully integrated into the small-scale indoor tire-road testing platform, achieving a sensing accuracy of up to 99% in measuring the revolution speed. Furthermore, real vehicle tests were conducted using a Volkswagen Passat, and the fitting goodness-of-fit for the vehicle speed perception still reached 99%, with a minimum real-time fitting accuracy of 80.25%. Finally, a high-performance vehicle emergency monitoring system based on the vehicle slip rate level was proposed for monitoring abnormal vehicle behavior, which could promote a safety upgrade of the autonomous driving technology.