demand and supply analysis presents the impact of increasing or decreasing the fare on the performance. it is an economic study. also, mode choice modeling estimate the perfect fare according to their income to reach the maximum utility from using such mode of transport.

we can share a research paper when data is avaiable

Anyone who doesn't pay the ticket price is simply committing a scam.

Regarding the "control services", it is not clear what you want to express about it.

I too am unclear what you mean by "control services". Do you mean some fares are subsidised to be free or like Giacchino are you implying many passengers just avoid paying the fare? Perhaps you could elaborate?

Also in addition to good suggestion to consider mode choice modelling suggested by Marwa, be careful to distinguish between "stated preference" and "revealed preference" mode choice surveys. In stated preference people tend to over-estimate the amount they will pay for certain features (eg higher frequency, quicker travel time, better comfort etc), whereas revealed preference will reveal what people are actually willing to pay.

I also agree with Marwa that at the core is an economic study - care is needed in the definition, the questions and the way representative data is collected and analysed. Even the best in this field can get it vastly wrong, so suggest you do a lot of reading and consult an expert. You could search for papers by Prof Neil Douglas (New Zealand) and Prof David Henscher (Australia) as two people with expertise in this field. I would suggest you also read the papers of their peers to gain as broad an understanding as you can.

Best of luck!

Hi, I mean fare evasion.

Sorry for my English.