I have a friend who is easily irritated and shocked by the slightest violation of traffic laws. Thinking of a phrase to describe him, I right away said to myself the word "prudish" would apply, but only if it is related to sex. As I have learned from the English language, you can use the adverb + adjective to characterize something like "Sexually embarrassing, Intellectually embarrassing, Emotionally compelling, Emotionally driven. So I applied the logic to describe this friend of mine and I said it would be "Trafficaly prudish" But I know such word doesn't exist. What words or phrases would describe him?
A suitable word might be
stickler - a person who thinks that a particular type of behaviour is very important, and always follows it or tries to make other people follow it
You could say
He is a stickler for the rules of the road.
I would probably use uptight, meaning "inhibited, worried, ‘on edge’; angry, ‘worked up’" (OED)
Fred is so uptight about minor traffic violations.
Hypersensitive, as given in another answer, would also fit.
I would not likely use pedantic as that implies more that the person wants to tell you, in detail, about the nuances of traffic laws, than it tells you about their emotional reaction to seeing someone violate traffic rules.
Prudish and prude refer only to sex or nudity. So its usage has not been applied to other things. Thus, for the situation you describe, you have to use other words, and
Adhering excessively to law or formula: our conciliation process avoids an overly legalistic approach narrow legalistic definitions
Excessively concerned with minor details or rules; overscrupulous
come to mind, mainly because someone who is legalistic and/or pedantic is often judgemental about how other people do things, including how other people drive; and someone who is legalistic or pedantic about the right way to drive (= not committing any violation of traffic laws) could be said to be
easily irritated (but not usually shocked) by the slightest violation of traffic laws.
Man, he's really legalistic about traffic laws.
Gee, he's pedantic when it comes to obeying traffic laws.
Or you could call someone who is "shocked" at the smallest violation of traffic laws
hypersensitive when it comes to traffic violations.
Having extreme physical sensitivity to particular substances or conditions.
Easily hurt, worried, or offended
But I don't think there's anything more specific than words such as these (and other people may suggest other such words).