I don't know about buses, but in the 70s, local trains on trunk lines ran every 4-5 minutes during rush hour compared to every 2-4 today. In total, there were about 6600 daily trains compared to 8200 in 2016.

https://www.nytimes.com/1976/08/14/archives/215-more-daily-subway-runs-will-be-eliminated-by-aug-30-215-more.html

http://web.mta.info/nyct/facts/ffsubway.htm