I found this article while browsing the AASHTO Journal:
APTA Study Says Higher Transit Use Results In Fewer Traffic Deaths, https://aashtojournal.org/2018/08/31/apta-study-says-higher-transit-use-results-in-fewer-traffic-deaths/ [Last accessed: 9/5/2018]
The article contains a link to the report, which would be a good reference for those who want to show proof for the argument for public transportation development and use vs. dependence on cars. I think its possible to come up with our own version of the graphs shown in the report especially those that show less traffic fatalities per 10,000 residents vs. annual trips using transit per capita. However, this will require data collection and analysis for at least the highly urbanised cities (HUCs) in the country. I say at least because these cities would be the ones likely to have the resources to determine the stats necessary for such an assessment.