I have never used the Common Noise Assessment Method that they referred to, since it sounds like a European thing. But I used to work in noise control in the US and even published research on traffic noise modeling.

It sounds like this model would have assessed your home as having low noise impacts, since it's pretty sporadic. They usually are based on average daily traffic counts.

This research is establishing a causal relationship between the steady background noise and increased hypertension. Transient noise from horns or an obnoxious motorcycle are related, but outside of what they were looking into.