The reliable and robust design of vehicular networks in a simulation environment requires accurate modelling of real vehicular traffic profiles obtained from experimental measurements (inductive loops or other sensors). Moreover, these models help to design wireless communication protocols and analyse their suitability for multimedia communications under different operating scenarios while maintaining the quality of service (QoS). To determine the key traffic parameters, in this paper firstly, we have carried out a statistical analysis of real vehicular traces recorded at the M4 motorway. Secondly, we evaluate and compare the performance of a modified packet reservation multiple access (M-PRMA) protocol with idealistic and realistic channel characteristics (real measurements) for a microcellular motorway communication system under varying network load. The results reveal that incorporating the realistic channel characteristics severely degrades the performance of the system however, the performance can be restored by adjusting the receiver power threshold.