Traffic monitoring technologies have become crucial for modern manned and autonomous vehicles. They aim to ensure the maximum level of safety and dependability. The commonly used monitoring technologies based on conventional LIDAR (laser imaging, detection, and ranging), vision and ultrasound sensors are effective if there is a clear line of sight for the surrounding traffic field. However, some potential accidents and traffic hazards beyond the line of sight cannot be detected by the aforementioned sensors. Thus, dedicated sensors require means to detect other traffic participants even if they are not visible due to obstacles. In this paper, a new traffic monitoring concept for detecting nearby traffic activities occurring beyond the line of sight is introduced. The principle is based on a portable laser Doppler vibrometer (LDV), which is mounted on the vehicle to measure the roadway’s vibration noise induced by nearby traffic activities. First proof-of-concept field tests were conducted using a commercial LDV and realistic public traffic conditions. A statistical classification method based on the frequency features of pavement vibration measurements showed quite good performance for identifying traffic conditions.