Evaluation Study of Inertial Positioning in Road Tunnels for Cooperative ITS Applications

Global Navigation Satellite Systems (GNSS) are unreliable positioning sources in road tunnels, as the satellite signals are unable to reach deep inside the tunnels. As innovative technologies emerge within the transportation sector - e.g., with Autonomous Vehicles (AVs) and Cooperative Intelligent Transport Systems (C-ITS), higher availability, timeliness and accuracy of positioning services is demanded. In GNSS-denied environments such as road tunnels, Inertial Navigation Systems (INS) can leverage the use of accelerometers and gyroscopes to estimate the vehicle's position while the GNSS positioning signal is lost. However, these systems have proven to be unreliable in long tunnels, as noise artifacts in inertial sensors introduce errors which accumulate over time. This paper aims to investigate the impact of these on the positioning accuracy in road tunnels, through modeling a commercially available Inertial Measurement Unit (IMU) and simulating driving routes through various road tunnels within Norway, a country with a complex terrain and many road tunnels. Through these measurements, we also investigate if the positioning requirements of modern C-ITS applications are met in various tunnels, depending on the tunnel length and curvature. Finally, this work lays the foundation for developing a framework for designing cost-effective and reliable indoor positioning solutions for road tunnel environments.