All too often, the performance of vehicular communications is benchmarked for a single link only. A major challenge for performance benchmarking of multiple interacting vehicles is the definition of repeatable vehicular scenarios. In this paper, we propose and discuss an approach for performance analysis of the IEEE 802.11p standard in urban interference channels, by linking network simulations with a Software Defined Radio (SDR) setup. This approach provides communication performance measurements in the worst-case interference scenario caused by an urban traffic jam. We do this by starting out with vehicular traffic flow simulations and continue to model the medium access. We furthermore introduce an algorithm to reduce the complexity of the communication network while retaining its properties. Finally, we use a setup of SDRs encompassing of communication nodes and channel emulators that emulate urban channels to measure the packet level performance as a function of Signal-to-Interference Ratio (SIR) and distance to receiver under urban traffic conditions.