Making NGSIM data usable for studies on traffic flow theory: a multistep method for vehicle trajectory reconstruction

Despite the undoubted importance of NGSIM data for the research on traffic flow theory, they were proved to be massively affected by measurement errors in the spatial coordinates of the vehicle, further amplified in the differentiation process when calculating speeds and accelerations. If not properly accounted for, these errors would make NGSIM data not usable for any study on traffic flow theory. However, we argued herein that the techniques applied so far in the literature to correct vehicle trajectory data are not suitable for the scope, as they did not treat appropriately the “cause” of the bias, while limited to smooth out the “effects”, that are the high and medium frequency disturbances in the data. Therefore, in this paper we first illustrated the mechanism at the basis of the errors in the NGSIM data, and showed the limits of currently available techniques. Secondly we clarified that extremely high errors, the outliers, need a special treatment to be fixed. In this light, we presented a multi-step filtering procedure aimed at i) eliminating the outliers that give rise to unphysical values for the acceleration by the local reconstruction of the vehicle trajectory, and ii) cut-off the residual random disturbances from the signal, still preserving the driving dynamics (vehicle stoppages, shifting gears, etc.). Both the operations were performed taking directly into account the requirement for internal consistency of the trajectory, that is the consistency among space travelled, speeds and accelerations. Though the procedure is absolute general, and can be applied to whatever vehicle’s trajectory, in this paper we first presented the results related to a single vehicle’s trajectory from NGSIM I80 dataset, and, then, those from the application to the complete set of trajectories from the same dataset. Results here presented motivated the need to correct NGSIM data before any further processing

MONTANINO Marcello;  PUNZO Vincenzo; 

2013-02-28

Transportation Research Board of the National Academies

JRC76757

https://publications.jrc.ec.europa.eu/repository/handle/JRC76757,