An advocate of more pipeline regulation said this year: "Until there is a rupture nearby and you can smell skin burning, people really don't pay attention." That has been the pattern throughout the history of government oversight of pipelines: explosion, death, reform.

1965 - A transmission pipeline explodes outside the small town of Natchitoches, La.

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Deaths: 17.

Reform: President Lyndon B. Johnson calls for the first time for federal regulation of pipelines. In 1968, Congress passes the National Gas Pipeline Safety Act, which authorizes federal oversight and mandates the first minimum safety standards.

1994 - A massive 36-inch pipe breaks and explodes in Edison, N.J. No one is killed, but the resulting fire forced the evacuation of more than 1,500 apartment residents, of whom 100 were left homeless. Investigators found a gouge in the pipe, probably caused by excavation equipment years earlier.

Reform: This accident and others spurred the nationwide spread of One Call systems, so that excavators can call a hotline before they dig.

1999 - A pipeline in Bellingham, Wash., ruptures and leaked gasoline explodes.

Deaths: Two 10-year-old boys and an 18-year-old man.

Reform: In 2003, a federal judge ordered that $4 million of the criminal fines imposed as a result of the Bellingham disaster be used to fund a nonprofit, the Pipeline Safety Trust. The trust, located in Bellingham, has become the leading advocacy group for better pipeline regulation.

2000 - A natural gas pipeline explodes in Carlsbad, N.M.

Deaths: 12.

Reform: This accident led Congress, in 2002, to require pipeline companies to track the conditions of their pipes after they are put in the ground. This mandate, known as "integrity management," applies only to the 7 percent of transmission gas pipelines that are in highly populated areas.

2010 - Thirty-eight homes are destroyed when a gas pipeline explodes in San Bruno, a suburb of San Francisco.

Deaths: 8.

Reform: This accident, as well as fatal explosions in Philadelphia and Allentown in 2011, have given impetus to new reforms. Congressional leaders last week backed proposals to add more federal inspectors and increase maximum fines. Regulators have also proposed possible new safety requirements for large-diameter, high-pressure gas gathering lines in rural areas.