According to a study by Donald Appleyard (1970), those living on a street with light traffic reported having three times more friends and twice as many acquaintances on their street as those on a heavily trafficked street.
Living on a road with light traffic (2000 vehicles per day) = 3.0 friends per person and 6.3 acquaintances
Living on a road with heavy traffic (16,000 vehicles per day) = 0.9 friends per person and 3.1 acquaintances
Appleyard concluded that traffic does not just take over the physical space of the road. It had a 'zone of influence' which intimidates and takes over a space psychologically. As the speed and traffic increased, the 'zone of influence' grew and the area people described as their home decreased. Essentially, those on busy streets had less interaction with their neighborhood and were significantly less connected to it.