Abstract: A pair of wiper blades on a vehicle window are oscillated in opposing movement between an overlapping inner wipe arrangement, in which one of the blades overlaps the other, and separated outer wiper positions. In dynamic symmetrical overlap (DSOL) operation, the first blade during each cycle to reach its outer wipe position is brought back first to be overlapped by the other for the start of the next cycle. This will normally produce alternating symmetrical overlap (ASOL) operation with its advantages of lower maximum blade acceleration and stress, since the overlapping blade precedes the other on the way out. However, if the leading blade is occasionally slowed, the other blade will not be forced to wait in its outer wipe position; and the cycle time will be minimized.