Sorry buddy, I can't give you anything other than my anecdata. No knowledge on whether anyone has done any studies on this specifically but lack of public infrastructure contributing to the income disparity has been widely studied.

It was hard enough for me to take the GRE when I went to a uni of 50,000 in a city of around 1 million. The testing center on campus naturally was booked out long in advance. Nearest center was 35 mins away in the outerbelt suburbs in another county at that point I believe, in some huge office park on a stroad without sidewalks nowhere near any bus lines. If I didn't have a car to borrow, there would have been zero way for me as a college student to get to this student testing center short of reserving three hours per leg to bike on de facto highways, which is baffling, but that was the reality.

Is there evidence that physical access has improved? The idea that you’re espousing, that things must have gotten better, is a belief that needs to be backed up.