Chemical producers say erratic rail service has forced them to curtail production of essentials like chlorine used to treat public drinking water systems and the plastics used in medical products.

And one of the nation's largest retailers of diesel fuel, renewable diesel, ethanol, and diesel exhaust fluid says Union Pacific's plan to cut its shipments by 50% will create fuel shortages, bring trucking to a halt, and raise prices at the pump.

Those were among the shipper concerns raised on Wednesday during a second day of hearings on railroad service problems that have been created by a shortage of train crews.

"The nation's supply chains are in a dire situation today because of this. And it's not getting better, it's getting worse. And the longer it goes on, the worse it's going to get," Ross Corthell, chair of the National Industrial Transportation League's rail committee, told the Surface Transportation Board.

He adds: "I don't want to be doomsday, but it's critical to our national security at some point in time. We have to be able to move commodities. And it's becoming more and more challenging every day."

Shippers complained about how lengthy delays, erratic service, and missed switches forced them to curtail or halt production or shift some shipments to more expensive trucks. Some products, such as chlorine and coal, have no alternative to rail. "We need to move coal and right now it's just not happening," says Katie Mills, a lawyer for the National Mining Association.