that assumes that city planners and civil engineers have a goal of battling these distributed deaths.

it's obviously a biased source, but "the war on cars" podcast has an interesting episode with Jessie Singer where she recounts her interviews with traffic engineers. A municipal traffic engineer's only goal is to shield the jurisdiction they work from from liability. as long as the industry standard best practices are implemented faithfully, you probably can't be sued. any attempt to do something different from the status quo opens you up to liability.