A computer is programmed to identify a target vehicle to be monitored and to identify first and second virtual boundaries on a roadway based on a position of the target vehicle. The computer is further programmed to determine a first constraint value based on (1) a first boundary approach velocity and (2) a first boundary approach acceleration and a second constraint value based on (1) a second boundary approach velocity and (2) a second boundary approach acceleration. The computer is further programmed to identify a maneuver of the target vehicle based on whether the first and second constraint values violate respective thresholds or a position of the target vehicle relative to the first and second virtual boundaries violates a threshold and to adjust a path of a host vehicle according to the identified maneuver.