Wireless communication systems are deployed for train to infrastructure communication needs related to guided transport applications (train, metro, tramway). These systems have to be operational in all transport environments and particularly in tunnels. Realistic tunnels geometries are generally of rectangular cross section or arch-shaped. Furthermore, they are mostly curved. This paper presents measurement results realized in a straight arch-shaped tunnel at 2.4 GHz and 5.8 GHz. The influence of transmitter-receiver location is studied. A statistical analysis in terms of slow and fast fading is realized. The measurement results are compared to simulation results with a modified Ray Launching method in order to validate the modeling approach proposed