We present the first steps towards an Open Source simulation and experimentation framework for IEEE 802.11p networks. The framework is implemented based on GNURadio, a real-time signal processing framework for use in Software Defined Radio (SDR) systems. The core of the framework is a modular Orthogonal Frequency Division Multiplexing (OFDM) transceiver, which has been thoroughly evaluated: First, we show that its computational demands are so low that it can be run on low-end desktop PCs or laptops and thus, the transceiver is also feasible to use in field operational tests. Secondly, we present simulation results to highlight the transceiver's capability to study and debug PHY and MAC variants in a reproducible manner. We show that the simulations match very well to a widely accepted error model for IEEE 802.11p networks. Finally, we discuss results from an extensive set of measurements that compare our SDR-based transceiver with commercial grade IEEE 802.11p cards. We made the framework available as Open Source to make the system accessible for other researchers and to allow reproduction of the results. This might also pave the way for future proofing cars by means of fully reconfigurable radios.