Interest in wireless communication systems in the vehicular domain is growing apace leading to the adjustment of current standards to be suitable for the more challenging and varying channel conditions. These adjustments lead to the introduction of the standards Global System for Mobile Communications - Railway (GSM-R), Long Term Evolution - Railway (LTE-R) and Intelligent Transport Systems operating in the 5 GHz frequency band (ITS-G5). First measurement results of ITS-G5 based communications for Intra-Train scenarios are presented in this paper. The performance of an ITS-G5 data link is analyzed and influences on the propagation channel from the inside and outside environment of the train are investigated for different link distances and different speed. The results show the possibility of applying such technology for Intra-Train communications for future wireless applications.