On October 15, 1997, at 0700 eastern daylight time, a Beech 1900D, N162ZV, operated by Mesa Airlines, Inc., and doing business as USAir Express, was substantially damaged when it was struck by a moving baggage tug, while taxiing at the Pittsburgh International Airport (PIT), Pittsburgh, Pennsylvania. The vehicle rolled over and the driver sustained minor injuries. The 2 certificated airline transport pilots and 12 passengers were not injured. One passenger sustained a minor injury. Visual meteorological conditions prevailed for the scheduled passenger flight that originated at Youngstown, Ohio, at 0635. An IFR flight plan had been filed for the flight conducted under 14 CFR Part 121. The Captain reported in a written statement that the First Officer was taxiing the airplane to the gate after landing. The airplane was traveling south on a taxiway when the Captain noticed the baggage tug approaching on an access road from the left, traveling west. The Captain stated: "...I noticed a fast moving vehicle westbound on an access road for bag carts that is perpendicular to the "Y" taxiway. I saw that the vehicle was not going to stop and I immediately applied the brakes [to] stop the aircraft. The bag truck collided with the left wing." The First Officer stated he was alerted by the Captain, but never saw the vehicle. According to the Allegheny County Police report, the baggage truck driver said he may have lost consciousness after striking a bump in the access road. The driver stated, "...the tugs have no suspension on them. When I hit the bump, I bounced...All that I remember seeing was a wing then rolling over." The report also stated the bump was at the point where the access road intersected the taxiway, and the intersection was controlled by a stop sign on the access road. The Police Officer reported issuing a citation to the tug driver for violation of Allegheny County Ordinance Four. Section Three. Subsection E, Air Operations Area (AOA), which stated: "Aircraft always have the right-of-way in the AOA. Vehicles needing to traverse an AOA ramp shall...obey all posted signage."