Ruptures of long seams in old oil and gas pipelines, like the one that dumped some 210,000 gallons of heavy oil into a Mayflower subdivision in March, account for as few as 4 percent of all U.S.

The National Transportation Safety Board's interim report on the Sept. 9 natural-gas pipeline rupture and explosion that killed eight people in San Bruno, Calif., focuses on defective pipe welds as a ...