Domestic container volume showed 9% year-over-year gains in the second quarter, largely attributable to a strong big-box segment, with total intermodal traffic rising by 2.4% for the quarter, according to Intermodal Association of North America(IANA).

International volume was unable to build on its solid Q1 growth, falling 1.3% in Q2 after posting 3% gains in Q1. This decline can be attributed to surprisingly weak shipments in June, with loads falling 6% from a year ago. It is unclear if the June trail off is an indicator of more to come or if the 6% dip is an outlier.

Intermodal trailer volumes declined 2.5% when compared to 2012’s Q2, but this loss was less than half of the decrease in loads experienced in Q1.

“Domestic container volume was the foundation of intermodal growth in both the second quarter and year to date,” said Joni Casey, President and CEO of IANA. “Despite some segments slowing in Q2, the Market Trends and Statistics data confirm the industry’s underlying momentum.”

Intermodal marketing company (IMC) volume slowed and intermodal loads ended up gaining only 1.1%, as opposed to 2.2% in Q1. However, while weakening imports and related transloads may have contributed to Q2’s performance, stronger gains in highway volume helped offset the slower growth in intermodal business.

South Central regional volume saw an improvement over double digit declines in international traffic, posting just a slight drop from the previous year.. The South Central region of the United States also saw its share of total intermodal traffic decrease by 1%, from 8% in 2012 to 7% in 2013.

Regional traffic in the Southeast United States grew 8.1% compared to Q2 2012, with domestic container volume leading the way up 12.4%, surpassing the industry average of 9% growth. Southeast international intermodal also bested industry statistics with a 6.7% gain compared to a 1.3% drop nationwide.