In this letter to Engineering News, Katharine McKenzie calls on the Department of Transport to provide more accurate information on the number of passengers that make use of the Passenger Rail Agency of South Africa's (PRASA's) train services.

As an occasional rail commuter, I follow stories about PRASA with interest. I would like to draw your attention to the potentially misleading use of passenger rail numbers, which is confusing for readers and lay people and can be inaccurate.

PRASA is fond of using ‘passenger trips’ as a metric of growth – this refers to the number of unique trips on passenger rail in a given period (a day, week, month or year say). This is often confused with the number of passengers using the service.

The first paragraph of your story says that passenger numbers in Cape Town reached 53 000 a day in April last year (a very low number for a city of about 4.7-million people). The second paragraph says this number has now almost doubled to 104 000 passenger trips a day. These statements are contradictory as a passenger trip is a unique trip – most passengers will travel twice on the system each day – 104 000 passenger trips implies 52 000 passengers.

A few paragraphs down the chairperson of Parliament’s portfolio committee is quoted as saying that Cape Town’s Central Line carried two-million passengers daily during its peak. This should be fact checked. If there were two-million passengers on the system daily that implies four-million passenger trips – the system has never had that kind of capacity in Cape Town.

Further in the article, the subheading reads “77-million trips a day” – this implies 38.5-million passengers a day on the system, if each passenger does a return trip. That would be a significant percentage of the entire South African population and a basic straw poll would suggest that this is not the reality of our commuter rail use.  

In the body copy underneath this is restated as 77-million trips over the past year. Still an impressive-sounding number; however, if that is divided by two to get closer to the unique number of people using the system and then divided by 365 days in the year, I get 105 479 passengers nationally on the commuter rail system as a whole – a very small percentage of the country’s commuters.

My main point is that by providing ‘big numbers’ in the millions, a fine-grained analysis of what is happening in the system is missed. The annual budget for PRASA is about R20-billion and there is a need to reflect more deeply on the return on investment this represents for the country.