Abstract: A transport system installed in a cleanroom where clean air is caused to flow from a ceiling toward a floor. The transport system includes a vehicle for transporting loads, and a guide rail suspended from the ceiling to guide the vehicle. The vehicle has a main body for running along the guide rail, a load supporting deck disposed over the main body, and connecting members for interconnecting the main body and load supporting deck. The guide rail is enclosed in a tubular cover defining an opening extending longitudinally of the guide rail for receiving the connecting members. The cover has a substantially streamline configuration with respect to the direction of clean air flows.