(Bloomberg) — To understand why more than 100 container ships are waiting to enter U.S. ports from Southern California to Savannah, Georgia, it helps to keep tabs on the congestion that’s building at another key junction of freight transportation: rail yards.

The so-called dwell time for containers at 11 major railroad depots reached an average of 9.8 days this month, according to a tally of its own boxes maintained by Hapag-Lloyd AG, the world’s fifth-largest container carrier. That’s up from 6.7 days in May and 5.9 in February.

Los Angeles leads the pack, as containers take an average of 16 days for them to arrive. In Charleston, South Carolina and Detroit, delays are increasing. There are some positive changes in Long Beach (California) and Kansas City.

Hapag-Lloyd, in an emailed message this week, stated that port officials will be extending their hours to night and weekend to alleviate pileups at intermodal lots clogged with empty and full containers. The delays through the ports of Los Angeles and Long Beach in particular, it said, “are expected to continue for the remainder of the year.”

On top of the strong demand for imports, a big part of the problem is a shortage of truck drivers to collect and drop off the 20- and 40-foot steel boxes, as executives of packaged good giant General Mills Inc (NYSE:). An earnings conference call on Wednesday highlighted this fact.   

“So we have literally hundreds of disruptions in our supply chain and it really changes on a daily and weekly basis,” said Jonathon Nudi, group president of North America retail at General Mills. “The bulk of our discussions right now with retailers are really around service and making sure that we can ship the product that our consumers are ultimately looking for.”

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