V2X data dissemination delay for vehicular traffic density estimations Distributed Floating Car Data (DFCD) corresponds to vehicles directly exchanging their floating data and cooperatively estimating the local traffic density instead of letting this task to the cloud. With a fully distributed approach, DFCD exhibits salient advantages in particular related to low latency and high reactiveness for smart mobility applications. This work proposes DissFlow, a DFCD solution relying on the knowledge of data dissemination delay of Vehicular-to-Everything (V2X) communications to estimate the underlying vehicular traffic density. DissFlow is first analytically formulated and analyzed, before being evaluated by simulation means on the iTETRIS platform. Considering a 1-D road network modeled by SUMO, simulation results show that the knowledge of the V2X dissemination delay allows to closely estimate and follow the evolutionary trend of vehicular traffic density.