One security expert says the Boston marathon bombings are not a reason to start worrying about your own security in large crowds or on mass transit systems.
When the train doors close behind you on Metro, maybe somewhere in the back of your mind you are thinking, "What if? What if Metro were targeted by terrorists?"
"The odds of you being killed by a terrorist are less than you being hit by a meteorite," says security expert James Carafano.
That may be an exaggeration, but you get his point. Carafano, who works for the Heritage Foundation, says commuter rail has to be an open system in order to move people efficiently, and making it a harder target would result in a lot of money spent with little to show for it.
"We live in a country with an infinite number of vulnerabilities," Carafano. "If you want to spend $20 billion on whatever, we are going to be at infinity minus one vulnerabilities."
Potential explosives on the Metro system are addressed through a number of overlapping approaches, according to to Metro spokesman Dan Stessel.
"We use a variety of tactics and technology, including K9 teams, specially trained officers on the Anti-Terror Team, random explosive screening of packages, sensors, cameras, etc.," Stessel says. "This combination of countermeasures is widely considered to be the most effective way to provide layers of security for an open system."
Stessel adds that Metro security also relies on observations by its employees and customers. In other words, if you see something, say something.
Carafano also says it's prudent for Metro to increase security after what happened in Boston — that any mass transit should have what he calls a "ladder of security measures" ready to be implemented in the event there is an actual threat or plot.
Statistically, an American in the United States being killed in a terrorist act is one of the most improbable things that can possibly happen.