Adding to what has already been said, I would keep in mind that consent is only one part of the picture, knowledge is another. This doesn’t just mean, or primarily mean, knowledge you have locked up in your brain somewhere, but actual reflection on the moral nature of the act at the time you give your consent to it.
To me, the angry thought at the other driver sounds like it might be something you gave your consent to, even gave it forcefully. Yes, strong spontanious emotions can reduce the voluntary character of an act, but on the other hand one can delibarately foster or at least co-opt emotions to add force to one’s decisions, in which case in my judgement the consent of the will is if anything strengthened, not reduced. One needs self-awareness to distinguish between the two situations.
Whichever case it is here (or one followed swifty by the other), it does sound like a spur of the moment thing, without first reflecting on the moral nature of the choice to give in to uncharitable thoughts. Once your conscience caught up with your will, it sounds like you repented of the wrathful thought the senario you described.
I’m not a mind reader of course, but to me at least that sounds like the situation you are describing.
Since I’ve brought up this issue of knowledge of the moral nature of the act at the time you commit it, let me just mention in case anyone might misunderstand that making an attempt to avoid reflecting on the moral nature of an act in order to morally “get away” with it will not exempt someone from culpability for it. By doing this they prove that they already know that the act is wrong or may be wrong, and they are lying to themselves and in a sense to God on top of it all. The Catechism of the Catholic Church says:
“1859 Mortal sin requires full knowledge and complete consent. It presupposes knowledge of the sinful character of the act, of its opposition to God’s law. It also implies a consent sufficiently deliberate to be a personal choice. Feigned ignorance and hardness of heart do not diminish, but rather increase, the voluntary character of a sin.”