Data is collected related one or more objects proximate to a first vehicle, the one or more objects including a second vehicle. The collected data is used to generate a virtual map of the one or more objects including the second vehicle. It is determined that the second vehicle is likely to pass within a predetermined distance of the first vehicle, thereby identifying a threat of a collision. An action is initiated based on the threat. The predetermined distance is determined by comparing a current traffic density to a predetermined traffic density threshold.