Detroit-Windsor Tunnel officials have installed 56 video cameras.
They monitor the nine million vehicles that annually pass through the one mile US-Canada border crossing, keeping them in sight from toll booth to exit.
The cameras are part of a $30 million renovation of the tunnel, which was built for $23 million and opened in 1930.
Tunnel officials say the monitoring is needed for the safety and efficiency of the tunnel. They say its main use is to watch for vehicle accidents or breakdowns.
There also is an unspecified anti-terrorism technology installed at the tunnel by the US Department of Homeland Security after the 2001 terror attacks.