Traffic is backing up on the I-74 Bridge because a maroon car is stalled in the middle of the bridge in the right lane. This according to a report from WQAD. Cars are slowly merging into the left lane to get around it. Traffic is backing up to 12th Avenue in Moline.

If you have travel plans taking you across the I-74 Bridge into Iowa, you may want to adjust your route to use another bridge. Here's some more traffic cams showing the back up:

Iowa Department of Transportation Traffic Cam at 12th Avenue.
Iowa Department of Transportation Traffic Cam North Tower to Iowa