This is What's Trending Today.

The area around the California city of San Francisco has some of the worst traffic in the United States.

One of the main bridges that connects San Francisco with Oakland, another big California city, is called the Bay Bridge. It goes across the San Francisco Bay.

An average of 270,000 cars cross the Bay Bridge every day. If anything stops traffic on the bridge, it becomes a big problem.

In 1989, an earthquake caused part of the bridge to collapse. The bridge was closed for a month before repairs were complete. San Francisco drivers were not happy.

This past weekend, on the morning of April 3, police officers on motorcycles stopped traffic on part of the bridge. The traffic lanes on the normally crowded bridge were empty, except for some police on motorcycles...chasing something down.

What were they chasing?

A small, black dog, called a Chihuahua, running around on the bridge. Although the dog weighs only about 5 kilograms, it could run pretty quickly.

Police had trouble catching the dog. They finally caught with the dog by throwing a piece of clothing on him. They saved him from getting hit by any cars.

On social media, people joked about the "high-speed" police chase. One Twitter user said, "What can shut down one of the largest bridges in the United States? An adorable Chihuahua it seems."

And that's What's Trending Today.

I'm Ashley Thompson.

Dan Friedell wrote this story for Learning English. Kathleen Struck was the editor.