To my mind, it would have to be some form of an attack, if untargeted, at least hundreds of cars, and if small would have to be targeted and strongly political,

To my mind, it would have to be some form of an attack, if untargeted, at least hundreds of cars, and if small would have to be targeted and strongly political, dangerous stupidity in a single instance for the purposes of having a good press story, doesn't qualify as either causing terror, or having an intent to, notwithstanding the broad legal definition that has been adopted over the past 15 years.