1. 1 University of Žilina , Department of Railway Transport , Univerzitná 8215/1, 01026 Žilina , Slovakia
2. 2 Technical University of Ostrava , ENET Centre , 17. Listopadu 2172/15, 708 00 Ostrava - Poruba , Czech Republic
3. 3 University of Zagreb , Faculty of Transport and Traffic Sciences , Vukelićeva 4, 10000 Zagreb , Croatia