pNEUMA is an open large-scale dataset of naturalistic trajectories of half a million vehicles that have been collected by a one-of-a-kind experiment by a swarm of drones in the congested downtown area of Athens, Greece. A unique observatory of traffic congestion, a scale an-order-of-magnitude higher than what was not available until now, that researchers from different disciplines around the globe can use to develop and test their own models.   How are the .csv files organized? For each .csv file the following apply: each row represents the data of a single vehicle the first 10 columns in the 1st row include the columns’ names the first 4 columns include information about the trajectory like the unique trackID, the type of vehicle, the distance traveled in meters and the average speed of the vehicle in km/h the last 6 columns are then repeated every 6 columns based on the time frequency. For example, column_5 contains the latitude of the vehicle at time column_10, and column­­­_11 contains the latitude of the vehicle at time column_16. Speed is in km/h, Longitudinal and Lateral Acceleration in m/sec2 and time in seconds.   For more details about the pNEUMA dataset, please check our website at https://open-traffic.epfl.ch