Traditionally, the communication and radar are separately designed. Recently, and with 5G technology, the Millimeter Wave (mmWave) spectrum becomes paramount for the exploitation of the large bandwidths. However, the interference problems have negative impacts on both radar and communication systems. To overcome these problems, the joint radar and communication (JRC) systems has been proposed as a promising technique that improves the spectrum utilization, allowing an optimal spectrum sharing and an efficient cooperative detection.In this paper, we propose an accurate performance analysis of JRC-enabled cooperative detection systems, where stochastic geometry is used to model the different vehicle positions in a given JRC systems. We derive closed form expressions of the average cooperative detection range (CDR) for different scenarios, with a different number of vehicles. Based on that, the general average CDR expression for a general number of vehicles has been derived. The results confirm the derived analytical expressions, which present efficient metrics to evaluate the cooperative detection in JRC systems.