Mercedes is one of the few cities valleywide where 20 miles per hour is the norm.
The Queen City of the Rio Grande Valley is known for narrow streets and homes without driveways.
The city's police chief says the reasons for the long time speed limit is obvious.
But why do so many drivers break the law?
The Speedzapper found plenty of cars to zap along 10th Street and Texas Avenue.
Click on the video camera icon for the wild ride!