Hello, we now live 100m away from a BUNDESSTRASSE, the house that is closest to ours in our new development area is 20m away. However, we have a noise barrier wall between the street and the houses, which absorbs an extreme amount of noise. And we all had to build soundproof accordingly, especially windows and sound-dampened supply air shafts. We only hear noise at night when a motorcycle accelerates or the federal border guard stationed here drives off on a mission with their water cannons.
In the apartment before, we lived 20m away from a heavily trafficked BUNDESSTRASSE (4 lanes and just before an intersection...), but the planting was done so cleverly that we only heard motorcycles accelerating hard or an emergency brake now and then. So, the noise wouldn’t shock me, build as far away as possible and then plant bushes/hedges that maybe even keep leaves in winter.
Regarding the 8m: we now live in a semi-detached house with a width of 6.5m. No problem. But you have to find out exactly what distances you have to keep and soundproofing will probably make the house more expensive than you plan. So, you can only have a house of your choice calculated with the development plan in hand before you buy the plot.
Best regards