The huge disadvantage of NFC in this context is the electronic waste necessarily produced.
To bolster your point, aren't there whole countries where stores and street sales float on top of QR codes?
China's Big Tech companies taught Asia to pay by scanning QR codes, but made a mess along the way
https://www.theregister.com/2024/06/17/asia_qr_code_obsessio...
Actually, I think part of the reason is that so they know who's on the bus in case it's involved in an accident, because if you buy a ticket from a bus station for a "short distance" (so out of the city, but within about 40km), you also have to provide them with a phone number even though they never call you or send you an SMS using that number.
The CCP certainly do want to know who's on the bus, but not for the reasons you stated.
Transit has to work offline.
QRs are dramatically slower than NFC.
I still use a physical card - so that I have a backup option in case something happens to my phone - but even there the volume of waste is trivial. I've had my current transit card for ages, and it doesn't expire until 2037. It's possible that the only technological decision I've made that generated less e-waste was deciding to splurge on a mechanical watch instead of a quartz model.
Which is not something that you could do with a QR system. I don't know that anything is inherently wrong with QR codes, but they do seem to be a choice that's more appropriate for countries like China where the existing electronic payment infrastructure uses QR codes. In North America, by contrast, things have generally settled on NFC, and I think that that reason alone probably makes NFC the better option for North American transit systems.
I've got several apps that display QR codes on the screen for an external reader. One of them is for my health insurance id card (a simple 10 digit number), another shows my COVID vaccination status (this one is complicated, and I'm not sure why they used a QR code for it. It must include batch identification and other information given the size)
With a QR code like that, people still need to install an app, set up an account, etc. It's just a lot more friction. In cities where I can tap-to-pay, getting set up to ride a bus or train for the first time takes literally zero time; I'm already set up. If I need anything special - apps, accounts, system-specific QR codes, etc - then the setup time instantly goes up to a minimum of 10 minutes. It's a relatively large barrier to entry for infrequent riders, and ultimately serves to discourage use of public transit.
Exit gates usually capture the ticket on exit when it has been used up (ie single journeys, or after the number of trips encoded on the ticket).
These can (and are) recycled numerous times.
So if you're replacing an existing magnetic system, you can reuse the magnetic transports (belts/motors etc) for single use, including capture-at-exit and recycling for single journeys, while also adopting the NFC for multiple use.
The QR codes are significantly slower to read than NFC.
I've built both NFC and QR (and ye olde fashioned magnetic stripe) ticketing systems.
2. As per 1, no issue
3. That’d be a great feature if true, I’m all for immutability. However , qr codes can be defaced easily, hopefully the built in checksum defend against that. a more likely threat your system needs to defend against is that new qr codes can be generated extremely quickly
4. Both systems are the same speed, both systems require accurate targeting by the user, an rfid token slightly askew of the reader will not read since it won’t be able to influence / absorb the generated rf - most of these systems work by providing power to the rfid token and it communicates back not by transmitting its own signal but by exerting influence on the signal it’s receiving. It’s a very very low power interaction and very sensitive to positioning
A better problem than 4 is that you entail staff overheads with a visual system to keep them clean.
Read / write is a bad feature, you will lose ticket sales.
Recycling these is not practical. Direct reuse risks jamming the vending machine (used tickets end up subtly bent, very hard to reliably deal with), actual recycling isn’t viable, the energy required and emissions produced exceed that of creation of a new card from raw materials.
Yes, the question is not whether such system would be abused, but how much. But this is in the end what businesses care about.
Will QR codes be abused more than NFC chips? Likely yes.
Will it produce a larger financial loss than the cost of the NFC chips?
Can I mitigate these losses by a centralized validation system (each terminal needs a network connection with low latency guarantees)? Sure, but how much will it cost?
[1] https://www.facebook.com/uktvads/videos/kerching-a-saverstri...
On 4, QRs are substantially slower to be read and decoded. NFC/RFID have a range of ~100mm and the field shape is dependent on the antenna design, however it is way more tolerant than QR using IR/laser. As for "entail staff overheads", we are talking about systems that process thousands of taps/day through single gates. Anything that reduces maintenance requirements is absolutely a priority.
As for "read/write is a bad feature", I don't really understand your point.
Ultralite RFID/NFC tickets are routinely recycled where they are used to replace old magnetic systems that have belt transports for the magnetic tickets. The read/write heads of the magnetic stripe are replaced with NFC readers but the belt transport and capture mechanisms remain.
You make it sound like less moving parts are a bad thing :-)
I know what you're getting at though - the decentralized tolerance of network partitions and the ability to provide higher availability and faster decision speed at the entry barrier.
The system design constraints are hard but not impossible, my back of napkin maths says 5k/ticket scans per second with 99th percentile latency < 1000ms not only satisfies every use case that exists today but allows for 3x population growth beyond!
There's a few things in your favour when designing this system though. For example, in the case of network partition, you have geographic locality so a pen drive delivered a couple of times per day is likely feasible.
The system I recently put in allowed for that 450ms, the time broke down to:
1) NFC comms ~100ms
2) Network comms ~50-100ms
3) Physical relays (releasing barriers etc) 100-200ms
During peak periods the usual rate expected is 30-40 passengers through a gate/minute, which includes all of the time above, plus the passengers actually walking through the barriers (usually ~2m).
The barriers at rail stations have to have a defined maximum throughput of passengers, because it affects safety during emergencies etc. Most barriers are required to maintain somewhere between 30 and 45 passengers per minute.
Yes they can "default be open" and usually have emergency modes that disable validation entirely, but the speed during peak hour periods has to maintain the passenger flow.
However, for most transit, there is some form of "check in/out" (either through barriers/gates or via validation/inspection). This is combined with rules about "antipassback" (ie one user passing the token back to another to reuse), as well as "total time in system" (ie to avoid people staying in the system all day).
There are also rules that take into account entry/exit times (eg peak/off-peak), entry/exit locations (eg core/non-core zones) etc.
All of these rules require either:
a) An always online set of validators to be able to contact the backend that is maintaining the information, or,
b) a way to record the information on the token so that it is physically transported from one validation location to another.
It also is needed for inspection purposes during a trip.
The problem with QR codes:
1. If they're printed, they can be copied.
2. "Dynamic" QR codes can be screenshot.
3. They're read-only (by definition)
4. Readers are slow, require good orientation by the user.
NFC is good because it's read/write, has a ~10cm range, the larger cards can hold up to 4K of data, the ultralights can replace single journey tickets and can be recycled like magnetics being captured at exit.