There's a study from Stanford showing the dropoff based on road traffic volume. The house I tested is 40 metres from a 30,000 cars/day road (2 lanes in each direction). The study suggests that the pm2.5 drops to the equivalent of the ambient air quality of the surrounding area at 37m away. An air quality sensor showed great AQI and no changes during rush hours.
That’s a good question when it comes to pollution but man, the constant whine of wheels on a freeway drives me insane.
For me it's the semi-trucks, modified passenger cars/trucks and motorcycles. Normal cars sound more like white noise. I used to live 2 miles from the freeway and could pick out the problem vehicles when there was an inversion layer to reflect the sound back to the ground.
And horns. I fuckin hate horns. I swear car horn noises reach into the far ends if the universe, you can't escape them.