A driver assistance system senses and provides an indication of an approaching vehicle located sidewardly and rearwardly within an immediately adjacent driving lane to a host vehicle. The system includes left and right rear sensor units proximate rear corners of the host vehicle. The rear sensor units sense vehicles on respective sides and rearwardly of the host vehicle. When either rear sensor unit detects an approaching vehicle within the adjacent lane on the opposite side of the host vehicle therefrom, the rear sensor unit provides an opposite-lane warning signal to the other rear sensor unit. The system includes providing host vehicle driving path information to the rear sensor units for determining the path of the adjacent lanes adjacent to and rearward of the host vehicle. The path information accounts for curves in a roadway. Further, the rear sensor units detect the speed of a closing vehicle. When a left rear sensor unit senses a closing vehicle in the immediately adjacent left lane or obtains an opposite-lane warning signal from a right rear sensor unit, the left rear sensor unit provides a warning signal to an alarm unit for a vehicle approaching in the left lane. When the right rear sensor unit senses a closing vehicle in the immediately adjacent right lane, or receives an opposite-lane warning signal from the left rear sensor unit, the right rear sensor unit provides a warning signal to the alarm unit.