The Windsor-Detroit tunnel was shut down for three hours Sunday morning for an Emergency Response Exercise.

For more than 10 years, emergency responders from the U.S. and Canada have been working together on emergency preparedness by working on different tactical exercises.

This year, it was Detroit's turn to facilitate a mock disaster.

Captain Arnold Williams with the Detroit Police says the emergency situation can range from just about anything.

Sunday was his first time participating in an exercise like this.

"For this exercise, it could in any number of things. Because I'm actually participating, they don't tell me everything we're going to actually experience," says Williams.

"It's going to test our how we actually use our tragedies when we come to these incidents and also test the communication that we have among the different entities," he adds.