This project's study area is the Pingyang Expressway, spanning from K347+260 to K380+933, with a total length of 33.673 kilometers. The expressway was completed and opened to traffic in March 2012, designed for a speed of 100 kilometers per hour. The section includes 21 mainline bridges totaling 7563 meters and 4 tunnels totaling 4518 meters.

The study area is divided into two sections: The first section has a fiber optic cable length of 19.5 kilometers, with equipment installed at the Nanpingyang Management Center in Yuxian County, measuring the interval between Nanpingyang in Yuxian County and Hedi Toll Station, from K380+933 to K364+493, shown as the blue line in the figure below; The second section has a fiber optic cable length of 22.5 kilometers, with equipment installed at Hedi Toll Station, measuring the interval between Hedi Toll Station, Chakou Toll Station, and Haojiazhuang Toll Station, from K364+493 to K347+260, shown as the purple line in the figure below.

1. Vehicle Detection and Traffic Analysis Using Distributed Acoustic Sensing (DAS) Technology
   • Deploy high-precision distributed optical fiber acoustic sensors (HiFi-DAS) along highways to collect vehicle driving signals
   • Identify vehicle collisions through signal processing
   • Design alarm strategies based on spatio-temporal distribution of signal features obtained from DAS
   • Calculate traffic flow and vehicle speed using specialized algorithms