The Decentralized Congestion Control (DCC) algorithms in ETSI ITS standards [1] address the IEE 802.11p MAC and provide reliability of periodic broadcast messages at high density of vehicles. However, the deterministic relation between controllable parameters, e.g. transmit power, frame duration, frame transmit rate and channel clear assessment threshold, and the effects of DCC algorithms, e.g. channel busy duration, frame interference-free reception probability and frame channel access delay, is still unknown since a correct mathematical analysis of the hidden station problem in CSMA networks is lacking. In this work, the hidden station problem in a linear IEEE 802.11p broadcast network is analyzed based on analytical results developed in [18] employing a modified MAC protocol model based on [3]. Simulation results validate the new analytical model for linear IEEE 802.11p networks w.r.t reliability and latency performances of Cooperative Awareness Message broadcast. Evidence is given that the model not only is valid for single-lane highways but also provides good approximate results for multi-lane highway scenarios. Our MAC layer analytical model of IEEE 802.11p broadcast reveals the quantitative relation between DCC parameters and congestion control effects in closed-form solution for linear vehicular networks. ; Comment: 30 pages