The higher the speed and density of the traffic on a given street, the more of that street is dominated by movement and the less available for exchange, such as childrens' play and socializing with the neighbors. Automobile travel has other deleterious effects, especially its contribution to urban sprawl. The more spread out a city, the less viable its public transport system. As auto traffic increases, people are less likely to walk or use bicycles because they don't feel as safe. The development of roads, shopping malls and superstores like Walmart also destroys local commerce.
Small stores are among the first casualties of widened roads.
The death of the corner store is one important aspect of urban blight. As neighborhood shops close, local jobs are lost, and the possibilities for local interaction decrease. More crimes happen because there are fewer eyes on the street. The mass production and use of automobiles in the 20th century has been an unmitigated social and ecological disaster. Continued mass car production and use of fossil based fuels is ecologically unsustainable.