Air carrier pilot reported the useable portion of Taxiway Y at ORD airport was difficult to distinguish from the unusable portion; which was blocked by flashing barricades.

Narrative

Prior to secure for flight we set up for Runway 28 right. On initial contact ground gave us a runway change to taxi to 22 left. The taxi instructions were complicated and we were doing a continuous loop Taxi while accomplishing the runway change procedure. When we were eastbound on Papa; we were given clearance: left on Yankee; cross runway 28R; right on November; hold short of Runway 22L. While crossing Runway 28R; we realized the taxi line we were following was blocked all the way across with flashing barricades. We immediately stopped the aircraft on Runway 28R and informed tower that we were still on the runway. Just after informing tower we had stopped; we realized that the usable portion of Taxiway Y was to the right. We then turned right and slightly down the runway to the usable portion of Taxiway Y and informed the tower controller that we were continuing taxi as previously cleared.Once established on November; we held short of Runway 22 left completed the runway; change checklist and departed uneventfully. Reason for the report is to highlight that a portion of Taxiway Yankee at the approach end of Runway 28 right is unusable and they need to use the eastern portion of Taxiway Yankee when crossing from south to north.