1. Department of Forest and Environmental Engineering and Management, MONTES (School of Forest Engineering and Natural Resources), Universidad Politécnica de Madrid, 28040 Madrid, Spain
2. Transport Research Centre (TRANSyT-UPM), Universidad Politécnica de Madrid, 28040 Madrid, Spain
3. Department of Agricultural Sciences, University of Sassari, Viale Italia 39A, 07100 Sassari, Italy