The National Capital Planning Commission unanimously approved plans on Thursday to install security barriers along the perimeter of Union Station.

Citing security and safety concerns, Nancy Witherell, a historic preservation officer for the NCPC, explained that the plan, submitted by the Federal Railroad Administration, Amtrak and the Union Station Redevelopment Corp., would retain the 100-year-old train station’s traditional design while improving, in Witherell’s words, “physical security for the most serious types of events.” The NCPC reviews and must approve all design projects for federal buildings and memorials.

The plan calls for concrete bollards, or short vertical posts, to extend into Columbus Circle in front of Union Station to protect pedestrians from traffic in front of the station.

The location of the bollards ensures that “pedestrian crossing is as good as possible,” Witherell said.

The balustrades — metal barriers to prevent car traffic — and bollards will be painted black to match the columns in Columbus Circle, planners said.

“What we think we have is a plan that will minimize the negative effects that were initially identified but I think provides layered protection that’s necessary to protect the public,” said David S. Ball, president of the Union Station Redevelopment Corp.

Before the security project can be completed, the NCPC must still approve funding for a separate Columbus Circle curb- extension project, Ball said. He said the Union Station Redevelopment Corp. expects to start construction on the bollards in March.