'You can't sleep here:' On board a perilous freight train with families hoping to reach the US

On top of the rumbling freight train, the young man says he has been attacked and robbed. There is no shade from the burning sun in the day, nowhere to keep warm in the perishing cold of the night. But still, he says, this brutal journey is worth it.

Roberto, 23, told CNN he was escaping from Honduras, where the US State Department says violent gang activity is rife and police are ineffective.

"Due to crime in my country, we can't work, we can't do anything," he said.

Roberto is one of the tens of thousands of migrants who have been making the perilous journey to the US-Mexico border ahead of Thursday night's expiration of the Covid-era immigration rule known as Title 42.

Roberto fled the country with his two young children, he said, becoming emotional as he talked about them. "I brought them here to Mexico but they got sick, they almost died," he said. "I had to send them back to Honduras."

Roberto was still sick himself, wearing a mask to protect others from his coughs. He said this was the seventh train he had ridden on top of in the past 12 days as he, his father and his sister tried to find a new life. His sister is 15, he said. In other circumstances, she would be celebrating her quinceañera at home with friends and family. But home, for now, was an open train car heading north.

The truck contains metal construction beams, covered in plastic. There are a couple dozen people in this freight car alone, with dozens more riding on top of and within the other cars. The riders flatten cardboard boxes and use dirty clothing to try to give themselves some padding against the hard, uneven surface. But this is still the preferred kind of train car, as it at least offers some protection from falling off.