No Stupid Questions @lemmy.world tired_lemming @sh.itjust.works 1 yr. ago

How does an automatic road barrier decide when a vehicle is coming?

So just something that's been on my mind. At my workplace there's an automatic road barrier that lifts up and down when vehicles arrive. However, it's not used for a carpark system when people wave their tickets or something. It just goes up and down when a vehicle shows up.

However, it sometimes goes up for when say a pushcart is being rolled over whereas it wouldn't for a guy pushing a bin.

So tldr, how does an automatic road barrier decide that yes, a vehicle is coming, and therefore opens up?

20 comments

Same as traffic lights. "Inductive-loop traffic detectors use an electrically conducting loop embedded in the pavement to send a signal to the traffic control system to indicate the presence of a vehicle."
- So a large wooden horse could slip by without detection
  
  If the large wooden horse is full of men in metal armor, purely hypothetically speaking, would the loop still not pick up the large wooden horse?
  
  How about a wooden badger?
- This, it's like a metal detector but, bigger. Temporary boom gates might use infrared motion sensors like automatic lights. edit: "lights" like the lights some people have on their porch.
  
  It's bigger in overall structure size, but isn't really that big itself. It's just a wire loop, they can be installed into existing roads with minimal effort - they just dig a narrow trench and then seal it up, it doesn't require more tarmac.
- Huh, so that's a completely new concept I've learned today. Time to do more reading. Thanks!
  
  Check the road in front of the gate. Those loops are usually installed after the asphalt so there should be a loop patched up with tar a bit smaller than a footprint of an average car.
looks like it really depends, https://us.beasensors.com/en/segment/vehicle-sensing-solutions/barriers/ has some information about the specific sensora they use.
- Your URL code is wrong. [https://us.beasensors.com/en/segment/vehicle-sensing-solutions/barriers/](url), this gives the URL as text but the link is just URL.
  
  This is working URL code: https://us.beasensors.com/en/segment/vehicle-sensing-solutions/barriers/ although you could just type the URL and the website/app should make it a link automatically.
  
  Good bot
There could be a motion sensor behind maybe? It could be one of those places that have a bunch of coils on the ground, wherein a large enough mass of metal gets detected by changing magnetic or electric fields, or something else entirely
Could be a lot of ways- an IR beam some where before the barrier. A motion sensor (usually IR or IR+ultrasound). Possibly some sort of movement detection on the security cameras.

Or a magnetic loop sensor, which is my guess. (You’d see the other sensors.)

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