In wireless multihop data message transmission by multiple mobile computers in ITS systems, even though in an area with sparsely distributed mobile computers, mobility of a computer with transmitting data messages helps to achieve high data message transmission ratio. This paper proposes data message transmission along a sequence of roads detected by a GPS satellite navigation system. Due to combination of dynamic determination of intermediate mobile computers and a store-carry-forward approach, higher transmission ratio and shorter end-to-end delay are achieved even with high mobility and sparse distribution.