Say a company has a parking garage for its employees, and they want to track the traffic in and out. So they require that all employees put some kind of tag in their car window, and they have some kind of reader at the entrance to the garage.

What would be the best technology to use in this situation (assuming cost is the largest factor)?

My initial thoughts were RFID tags because they seem to be incredibly cheap if you're only looking to measure over a distance of a couple meters. Are RFID readers that can read over a couple meters a viable solution?

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    \$\begingroup\$ You are correct. In given range of distance, time window, cost and certainty for security sake, the RFID is the only option. I mean there is nothing better ever invented. \$\endgroup\$
    – user924
    Commented Jun 3, 2012 at 23:16
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    \$\begingroup\$ Is is just about the amount of cars going in and out or do you really need to track individual cars? Is the tag an assumption or a requirement? \$\endgroup\$
    – suha
    Commented Jun 4, 2012 at 8:41
  • \$\begingroup\$ @suha: It was more an attempt at trying to convey an analogous problem to the one I have. So the most up-voted answer being a solution specific to cars was unfortunate, but that was my bad. I think I've decided to go with RFID for my issue. \$\endgroup\$
    – Ryan
    Commented Jun 7, 2012 at 1:41

1 Answer 1


How about a plastic plate on each car with large, clearly readable numbers and letters? Say, one on the front, and one on the back. Let's call these 'number plates'.

Then have a camera at the entrance of the garage which contains some kind of computer which can read the numbers, and pass them along to another computer for processing.


Then you can record every car that comes in and out. Perhaps something like this is available on eBay.

  • \$\begingroup\$ Camera beats RFID on every front for this particular app. Easy to build, virtually effortless to deploy in cars and ultra cheap. (Easy to copy but there are ways around it). \$\endgroup\$
    – Ktc
    Commented Jun 4, 2012 at 1:41
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    \$\begingroup\$ @Ktc Unless the letters are obscured by something. Here in Colorado there will always be snow and ice. The OP didn't say where he is, but mud is an issue everywhere. \$\endgroup\$
    – user3624
    Commented Jun 4, 2012 at 1:44
  • \$\begingroup\$ @DavidKessner I was thinking a little differently. I was thinking this sticker was behind windshield, it has a retroreflector printing and you use IR LEDs to illuminate. I am 90% sure, I can pick up the writing on the sticker from a mild mud. \$\endgroup\$
    – Ktc
    Commented Jun 4, 2012 at 2:20
  • \$\begingroup\$ Why not use a license plate instead? \$\endgroup\$
    – avra
    Commented Jun 4, 2012 at 7:42
  • \$\begingroup\$ @avra - Er, isn't that what I said? Look at the picture. \$\endgroup\$ Commented Jun 4, 2012 at 9:39

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