You say "already in place". While it's certainly true that smog isn't anywhere near the problem it once was, it's still a problem, and others still pay for the consequences of automobile emissions.

Some quotes from various sources:

https://www.latimes.com/local/lanow/la-me-air-pollution-repo... - "Los Angeles remains the nation's leader in harmful ozone pollution from car tailpipes emissions ... but the report said the nation's second-largest city also achieved its best overall air quality score of all those years."

https://www.livestrong.com/article/156537-facts-of-car-pollu... - "The American Lung Association reports that 30,000 people are killed by car emissions annually in the United States alone. Air pollution also causes numerous respiratory and cardiovascular problems and may exacerbate pre-existing conditions such as asthma. More than half of Americans live in areas that fail to meet federal air quality standards at least several days each year."

https://www.pca.state.mn.us/air/motor-vehicle-pollution - "Motor vehicles give off more than half of all carbon monoxide and hydrocarbon emissions in Minnesota. These emissions, including microscopic particles, can contribute to breathing and heart problems along with an elevated risk of cancer."

https://owl.cwp.org/mdocs-posts/elc_pwp6/ - "Metals can follow many pathways before they become entrained in urban stormwater run off. A recent California study sponsored by the Santa Clara Valley Nonpoint Source Program suggests that cars are the dominant loading source for many metals of concern, such as cadmium, chromium, copper, lead, mercury, and zinc."