At Passenger, we maintain a publicly accessible glossary of common transport acronyms and terms. This tool has been helpful for many stakeholders working in and around digital, data, and transport, including our clients.
I’m sharing it here in case it’s useful for members of this forum, too. We’re adding to it all the time, so if there’s anything missing that you’d like to see, please drop me a line.
Nice one… but there’s a few obvious ones missing (e.g. PAYG)
Thanks Hayden, happy to add it. I’d be interested in your definition of Pay As You Go in the context of transit ticketing, i.e. is it pre-pay, as in ticket purchase before travel. And synonymous with Model 1 (retail) payment etc.
I would personally define Pay As You Go [PAYG] as a transport scheme/ system where you don’t need to buy tickets in advance of travel. Instead, you simply pay for your travel as & when you use it (e.g. Model 1 : as you tap when you board a bus or Model 2 : when you tap in & tap out when using a train).
Happy to discuss…
That’s interesting thanks, and not what I would have expected! Mostly because my understanding of PAYG is in context to things like mobile phones where a customer pays for data upfront before being able to use it. In this context PAYG is pre-pay, whereas a contract is post-pay.
I think this highlights some of the challenges in the industry! I would go further with the definition of Model 1 as to me this is where the customer boards a bus and asks the driver for a specific product rather than just tapping in. This is more akin to buying a coffee in Pret, for example.
PAYG does not necessarily involve pre-pay, for example, using a contactless payment card on the tube.
To me, PAYG in the context of transport means that the fare is calculated according to your actual travel pattern you are paying for the journey at the exact moment you take the journey , without buying a fare beforehand, which can be done by:
If using a contactless payment card (bank card), this term applies to model 2 only, not 1 or 3.
Ok, that’s interesting too. It would seem that your understanding is the same as Hayden’s in that PAYG equates to Model 2 (also known as Tap On, Tap Off). I’d be interested to know if the wider transit community shares this view.
The only point I’d raise is that customers are often not “paying for the journey at the exact moment you take the journey” with these systems. Normally the transaction is completed later so that charges for multiple journeys can be grouped together, and any discounts/caps applied, before the transaction actually occurs.
I understand, perhaps I should rewrite the description as “fare is taken according to the actual travel pattern”, which is not true for Model 1 and Model 3 (where you need to buy a fare product beforehand - in Model 1 you get a ticket, in Model 3 the fare is associated to your account).
Also, when Oyster PAYG was initially rolled out, it was called Oyster Prepay (the term still remains in some ticketing codes but is no longer used publicly), and clearly, the term “prepay” can’t be applied to contactless payment cards.
Ah… the combination of financial and transport terminology 
This page probably describes the 3 x Models of Transit payment best:
https://www.ukfinance.org.uk/policy-and-guidance/reports-publications/contactless-transit-emv-framework
Model 1
Is PAYG and paying AS you start your journey for a known product / fare.
Model 2
Is PAYG and paying AFTER you complete your journey (and therefore the product / fare is determined by some sort of Back Office)
Model 3
Is NOT PAYG, but relies on the use of some sort of account in the Back Office to store pre-purchased tickets - and therefore usually part of an Account Based Ticketing scheme.
Note: It gets really ‘fun’ when Model 2 and Model 3 are combined as a proposition
I don’t think that Model 1 (like shopping checkout) is PAYG, as the following is clearly Model 1:
As long as there is a physical ticket, it isn’t what PAYG means in the context of transport, regardless if you buy the ticket from the driver or from the ticket machine at the bus stop (some systems, such as suburban buses in Prague, allow both with no difference in cost or functionality).
The models can also be distinguished in terms of ticket inspection:
Model 1: the payment is taken in advance, the ticket obtained is the proof of payment
Model 2: the payment is taken during or after your journey, the card is the proof of payment
Model 3: the payment is taken in advance, the card is the proof of payment