(Portland, OR)  --  Some TriMet riders are among the first to test a double-decker bus.  WES riders had been taking commuter buses for three days because of work on track upgrades.  They were surprised yesterday when the double-decker bus showed up to take them from Wilsonville to Beaverton.  The bus featured a screen that showed riders which seats were available on the second level before they even went up there.