Source document: https://docs-lawep.s3.us-east-2.amazonaws.com/1698831458946.pdf (South Africa)
National Assembly Question No: 1570 1570.

Mr M M Chabangu (EFF) to ask the Minister of Transport: (1) What informed the decision to allow taxis to carry passengers at 100% capacity for local trips and at 70% capacity for long-distance trips: (2) whether he has found that people who travel locally are less infectious of Covid-19 than people who travel long distances; if not, what is the position in this regard; if so, what are the relevant details?
NW1946E REPLY (1) Medical experts and professionals advised that the longer you are exposed to an infectious person the more likely you are to be exposed to the virus.

This implies that encounters with an infectious person for a short time have a lesser risk of spreading the virus.
It is for this reason that allowing closer contact of passengers (100%) on shorter trips/period would not necessarily expose them to a higher risk of infection especially if this is coupled with other mitigating measures such as wearing masks and allowing ventilation.

A study was also done by researchers at UCT that was published.

(2) See answer for 1 above.