Firstly anyone giving a truly correct answer to this question should be immediately detained and questioned by Homeland Security and the FBI because only the terrorists themselves would truly know the answer here.

Next, all terrorist attacks are successful whether their actual desired effect was achieved or not. Just because the bomb did not go off in Times Square does not mean the attack was not successful because even the "failed" attacks slowly erode our feeling of personal and public safety. That is what terrorists do, they create an environment of terror and a failed attack is a slower erosion of our feeling of safety than a successful attack but every attack successful or failed is inherently successful to some degree.

"Recent attempted terrorist attacks, real or a way to gather data?
-Both, this attack was successful in every way except that no Americans died.

So this attack (Times Square Car Bomb) was a success even though it did not kill a single person. It certainly allowed the planners of this attack to measure our response, it allowed the rest of the terrorists in the world to also measure our response via media coverage, and it really did put a bit more fear into the hearts and minds of a least a % of Americans. That is successful terrorism.

This question itself is a result of the attack and is a measure of fear not previously here until the so called "failed terrorist attack". We are all have a heightened sense of awareness for possible "distraction" and attempts to draw attention from one place so they can terrorize from another vantage point, This is one of the most influential methods of terrorism as it allows our imaginations to take over and ... therefore we now live in a personally more fearful life and world.

Terrorism begins in our minds and the fear attempted attacks generate is just as successful at achieving the goal of terrorism as the actual killing of people in "successful terrorist attacks".

I may be wrong, but it feels like a chess match is happening in NYC. Currently the pawns are going first, bungling through, possibly getting lucky (but thank God, not). NYC is the soft spot because it's still sore from 9/11/01...and will be for some time to come. I pray that we as a nation continue to hold fast to striking at the hearts of our enemies and neutralizing the threats before they make reality here at home.