Trains carrying toxic gases should slow down while traveling through populated areas, a safety measure that could prevent chemical accidents like the deadly Jan. 6 crash in Graniteville, the National Transportation Safety Board said Tuesday.

The NTSB’s recommendation, which follows 11 months of investigation, is one of four suggestions to improve safety and avoid deadly chemical accidents on the nation’s railroads.

Other suggestions include requiring warning devices on non-signaled track and adding equipment that better protects train crews from chemicals.

Last January’s train crash in Aiken County caused a 90-ton chlorine car to rupture, which spilled gas that killed nine people and hospitalized at least 75 others. The Norfolk Southern wreck, the nation’s worst railroad chemical accident in nearly three decades, has sparked nationwide calls for train safety reforms and a push in South Carolina to slow trains through some cities.

The NTSB said Tuesday the crew of a train that parked on an industrial spur was to blame for the wreck.

Hours after the crew parked the train and left, a second train traveling at 47 mph through Graniteville ran off the main track and crashed into the parked train. The parked train’s crew failed to flip a track switch after pulling its train off the main line, the NTSB concluded.

If the conductor had held a briefing with his crew after they parked the train Jan. 5, the crew might have discovered the switch had not been returned to its original position, the report said.

“This was a tragic chain of events that did not have to happen and unfortunately resulted in the loss of life,” said NTSB acting chairman Mark Rosenker. “The board cannot stress enough the importance of following proper procedures and protocols, at all times, when operating these massive machines.”

The NTSB recommendations are being forwarded to the Federal Railroad Administration. It could be months, if not longer, before any action is taken, either by federal regulation or a bill in Congress.

Federal Railroad Administration spokesman Steve Kulm said the agency has been testing an electronic device to warn train dispatchers if a track switch is improperly aligned. Congress also ordered the agency in July to study tanker car safety and to set tougher standards for them.

The NTSB will provide a full response to the recommendations when the full report is completed, Kulm said. Tuesday’s recommendations were the executive summary of the report.

Norfolk Southern spokesman Bob Fort said he could not comment on specific suggestions until it reviews them.

“We have always regretted that this accident occurred,” he said. “I do want to emphasize that we are focusing on maintaining what is an excellent safety record.”

The safety board recommendations say the Federal Railroad Administration should require railroads to:

• Operate trains at speeds slow enough to stop if a switch is misaligned. The suggestion applies to stretches of track, known as dark territory, that do not have automatic signals to warn oncoming trains of danger ahead. Graniteville is in a dark territory.

• Put tanker cars at the back of trains and reduce speeds through populated areas. This reduces chances rail cars could rupture and release chlorine, anhydrous ammonia or other poisonous gases. The NTSB said a coupler, or device holding trains together, punctured a tanker car positioned in the midsection of the 42-car train.

• Install automatic devices, such as strobe lights, to tell railroad employees if a track switch is in the wrong position. Norfolk Southern workers who parked the train on the industrial spur were within 21 feet of the improperly aligned switch as they left for the night. None noticed it was in the wrong position. The changes would apply in dark territories.

• Provide breathing equipment and training to crew members who work on trains that carry hazardous gases. The NTSB said the engineer of the locomotive that crashed might not have died if he had emergency breathing apparatus.

Phil Napier, Graniteville’s fire chief who responded to the chlorine leak, said the changes should be enacted to spare other communities the suffering his town experienced.

“Any measures to prevent something like this from happening again, we need to work to accomplish that goal,” Napier said. “This year has been robbed from us.”

Reach Fretwell at (803) 771-8537 or sfretwell@thestate.com. The Associated Press contributed to this report.