Traffic at all major border crossings connecting Ontario and Michigan will be temporarily halted Friday morning as officials mark the anniversary of the Sept. 11, 2001, terrorist attacks. Border authorities say traffic will be cleared from ports of entry before 8:46 a.m., the time the first hijacked aircraft struck the World Trade Center in New York City. A ceremonial observance will then take place at each crossing, including the playing of taps as flags are raised, followed by a moment of silence. The temporary closures are expected to last about 30 minutes or less. The affected crossings include: Motorists planning to cross the border Friday morning are being advised to allow extra travel time and expect delays during the ceremonies. Normal operations at all ports of entry will resume immediately following the observances.