NEXT year's US$5 billion Panama Canal expansion will alter the competitive balance between the US east and west coast ports, says a study by Boston Consulting Group and CH Robinson.

"Companies relying on fast rail service will need to take a much more segmented approach," said CH Robinson analyst Sri Laxmana, reports the American Journal of Transportation. 

"When time is of the essence, the west coast may make sense, but in other cases, shipping through Panama will outweigh the extra time in transit," he said.

West coast ports will still handle more traffic than they do today, but will experience lower growth rates and their market share will shrink 10 per cent, the study said.

Today, goods from Asia through the west coast are railed and trucked as far east as the Ohio River Valley, but with the expanded canal's opening that will be cut back, the study said.

"The expansion will permit big, efficient postpanamax containerships, with two to three times the capacity of current vessels to reach the east coast," said a report summary. 

"Those ports will then become more cost competitive because it is cheaper to move cargo by water. West coast ports, however, will remain the destination of choice for shippers who need to use the fastest routes possible," it said.

The region in which east and west coast ports compete for customers will shift several hundred miles west toward Chicago and Memphis, covering a region that accounts for about 15 per cent of American GDP.

"With the Panama Canal's expansion, shippers will have more options and carriers will compete to provide those options," said BCG partner Peter Ulrich. 

In 2014, about 35 per cent of container traffic from the Far East to the US arrived at east coast ports, but growth trends will increase that to 50 per cent by 2020 with the canal's expansion. That’s a 10 per cent increase in market share.