RFID for high-speed tolls - Page 1
Forum section: electronics / rf-microwave

author: KD4CCF
author_rank: Contributor
timestamp: February 09, 2019, 04:31:50 am
content: It amazes me with driving on numerous Florida toll roads at, let's say 70MPH, that the tall 2-30ft overhead transponders can:a) trigger a response from a windshield "Sunpass" sticker, whilst going past at 70MPHb) gather required data from a plurality of vehicles in close proximity to each other in two adjacent lanesMost RFID I've been accustomed to have very short range.Any insight to how the toll system is able to handle this would be appreciated.T

author: Rerouter
author_rank: Super Contributor
timestamp: February 09, 2019, 04:49:20 am
content: Its a large array of transceivers, and the particular RFID method they are using is built to handle 10's or more tags broadcasting simultaneously, Its actually very similar to the coils they have in certain casino chips, so they can keep track of where large amounts of chips move (think theft prevention), and last I heard, they can track up to 400 tags a second going past a sensor area.From memory the second the coil enters the field area (like 8 meters out from the arch) it handshakes to determines the exact phase and frequency for that tag, locks to it and tracks it with multiple antennas to correlate its responses, from the handshake it has the Tag ID and possibly other data (but its small), uses a local cache to lookup the tag and sends the response to the tag, and issues an update to the toll system to deduct the amountI believe they also use basic road coils to detect when a car is under 50m away to prepare,

author: AG6QR
author_rank: Frequent Contributor
timestamp: February 10, 2019, 07:31:38 pm
content: RFID in things like ID badges is usually passive, with no power source in the badge, resulting in a power inversely proportional to the fourth power of distance. The power received by the badge is proportional to inverse square of distance, and this power is reduced again by another inverse square factor on the trip back.Toll tags typically are active, with a lithium battery inside the tag. The tag transmits a low power signal in response to an interrogation from the toll collection station. Since the power is supplied by the tag, not by the received RF, the received signal is proportional to the inverse square of distance.

author: KD4CCF
author_rank: Contributor
timestamp: February 11, 2019, 07:00:06 am
content: The window sticker types don't seem to have any battery... there's barely a bump for the electronics. If there were a battery, it would be so tiny and depleted in short order.

author: tautech
author_rank: Super Contributor
timestamp: February 11, 2019, 07:31:33 am
content: RFID ?Number plate recognition cameras are used here in NZ and then traced to the vehicle's register owner and a subsequent letter arrives demanding the toll....if you haven't already paid online OR are a registered user in which case the toll is automatically deducted from your bank account.

author: Rerouter
author_rank: Super Contributor
timestamp: February 11, 2019, 09:02:29 am
content: Here in aus they use a mix of camera ID and active RFID, some tag providers however charge you an extra $2 per toll for every photo ID match, which has been deterring its widespread usage, So I can only imagine to a toll provider there is some good reason they don't want a full rollout, as the tags and infrastructure for them are not cheap.Lucky for me a toll system in one state works with other states, so its literally a case of pick which has the best benefits, whereas I suspect most people just go for the name advertised by the toll road they drive on.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: February 11, 2019, 10:14:04 am
content: The ones I've seen use active tags, operating somewhere around 5GHz. Kapsch is one supplier. I have a tag somewhere in my teardown pile.

author: Stray Electron
author_rank: Super Contributor
timestamp: February 12, 2019, 01:45:02 am
content: Quote from: tautech on February 11, 2019, 07:31:33 amFlorida used to use an entirely electronic system that required electronic transponders but they're in the process of adding an automatic license plate tag reader to that. They're been warning people for some time not to use the transponders in another vehicle or the system could detect that the transponder and tag don't match and issue a citation to the vehicle owner. Also the system used to issue traffic tickets to anyone that didn't have a functioning transponder, even though the owner and vehicle tag was registered in their system and had money available in an escrow account that is held by the toll road operators. But now due to several law suits, the system now will not issue a traffic ticket to the owner of a vehicle that is registered in their system and that has funds available. They now check the photo record of the tag of any vehicle in question and if it is registered in their system (and has money in the account) then they just deduct the toll from the account and now send the owner a letter telling them that their transponder doesn't work and that they need fix or replace it, instead of automatically issuing a traffic ticket.Due to tourism and retirees and snow birds, Florida has a LOT of cars on the road that are registered out of state and that don't have transponders. In the past, they could run the toll booths and the toll road authorities couldn't effectively ticket them. The new system will read the license tag ofeveryvehicle that goes through a tool plaza and identify the owner and deduct the toll from their account, if they have one. In some counties already, I think that if you don't have an account the toll will be added to your county tax bill. I expect that before long Florida's system won't use any transponders but will use license plate readers entirely. I'm not sure how they will handle billing if you don't have an escrow account but I'm sure that they will find a way. My guess is that it will be handled like a municipal traffic ticket and that they will suspend your driver's license if you don't pay the toll plus a hefty surcharge. Similar, actually, to the way that red-light tickets from private companies are now issued and enforced all over the state of Florida.