CMA CGM, Maersk, MSC and Cosco are among mainliners charging add-ons on overweight containers.
Global vehicle carriers are set to feel the sting of a growing Chinese-operated ro/ro fleet amid a fight for international car cargoes.
The fees come as dwell times for refrigerated containers in Houston exceed a week and reefer volumes topped 10,000 TEUs for the first time in three years.