Yesterday we went to a mall and used the parking deck. They had new LED signs, indicating how many spaces were available in the various parking structures. Then, when you drove into the deck, there were signs saying how many spaces were available on each level, and in various parts of each level.
How do those work? And how accurate are they?
The most advanced systems have a camera (or other sensor) above each space (or set into the pavement itself), which detects whether there is a car there. One car park at a shopping centre I sometimes visit has little LEDs on sticks above each space, which show either red or green, so you can see at a glance as you look down the row whether there are any free spaces, without the usual thing of driving down there and finding that what you thought was a gap actually has a small car tucked into it.
More basic systems just keep count of the number of vehicles going in and out of the entrance and exit barriers, but those usually only give you a count for the car park as a whole, not each individual level.
There’s an overview of the different systems here: http://www.access-automation.co.uk/car-park-count-systems
One thing I didn’t know is that some car parks have a system of induction loops in the ground so that even if they don’t monitor each individual space, they can still keep track of how many cars have entered and left each part of the car park, so they can give a live count at each level.
It was cold, and I didn’t conduct a careful inspection, but I was looking for some kinds of cameras/sensors over each spot, and didn’t readily see them. And, no, there were not LEDs on each individual space.
I assumed it was some system of floor sensors, but didn’t know if they were for each space, or just at various traffic points. This was an older deck - so whatever tech they used, it was retrofitted. There were no visible sensor cables on the deck, for example.
As we drove from our space to the exit, there would be signs saying (for example) 125 spaces on this level, 207 on the 2d level. And on the same level, at an intersection it would indicate 55 spaces to the right, and 67 ahead. And the numbers changed as you progressed through the level.
(BTW - 5:30 on a cold Thursday in February - the mall was deserted!)
(Also BTW - I love your username. I used to collect colophons.)
I assume in that case they would be sensors buried under the concrete when the car park was built, which keep track of the number of cars taking each path from the intersection to figure out how many spaces are likely to be free. I doubt it’s a totally exact figure but it should be close enough.
I imagine if you had enough time on your hands you could game the system by driving round in a loop, avoiding certain areas by cutting through empty spaces, and confuse the system into thinking the car park was full 
Thanks! Does Spiny Norman mean anything to you?
Yeah, but like I said, the deck predated the signs. So I was looking for - and did not see - signs of concrete cuts/patches. Which would have been (IMO) a pricey retrofit.
What, other than another poster around here? 
Although I bet some do it with other sensors, doing this with a few strategically-placed cameras is a pretty darn simple computer vision problem. Cars do not look very much like empty parking spaces, and there’s not really anything else that blocks a parking space and doesn’t move for a long time.
Putting up a handful of cameras is a lot cheaper than digging into concrete to place induction loops.
And you kinda want security cameras that can see most of the spaces anyway for crime-prevention reasons.
Wow! Never thought of that. Makes sense. Thanks.
did she die in vain?
Our Self-Park Garage has a simple mechanical counter attached to the swing-arm gate at the entrance and exit It is up to the parking cashier at the exit booth to periodically tally the ins and outs to radio in to management the count: maybe, someday, the system could be upgraded to be electronic/automatic. :rolleyes:
Whoever invented those red/green LEDs can go to hell. I’m colorblind and they look the same to me.
<rant>At work, we have to hold our badges to a sensor located outside to unlock the door to get into the building. The door that it unlocks is in the vestibule. The door going into the vestibule from the outside is always unlocked. Well, the sensor only works half the time, but it does give a green or red light indicating if the door unlocked. I can’t fucking tell the difference, so half the time I swipe, walk into the vestibule and the door going into the building is still locked, so I have to go outside again and try it again, repeat until it works. You know that tiny bit of embarrassment you get when you try to open a locked door in public? Well that happens to me several times a week. Why won’t someone think of us color-blind people when designing these things??</rant>
Simple photocells at traffic choke points like entries and exits on ramps about two feet up will do the trick without needing to saw cut the pavement to install sensor loops.
IR beams at intersections are an easy retrofit and discrete.
OK, be fair. Let everybody else in on the drift here…
How do you distinguish red and green lights controlling intersections?
Not necessarily so pricy.
(in your situation, you saw no evidence of cuts, so the following is not about that garage)
Around these parts the guys put in induction loops by coming in after the road is built and using a circular saw to make a shallow rectangle where they want the loop. They make four long cuts, for the sides of the rectangle, then make four smaller diagonal cuts to lop off the corners of the rectangle. (pictures)
Then they saw a line from the loop to the street corner, where the control unit is.
The kerf of the blade is wide enough for the induction wire. Slip the wire in and patch over the top. The whole process probably is done in a few hours.
Position. The red light is always on top, unless you’re someplace weird like New York City that has horizontal lights. Not a big deal at intersections but trying to discern if one light in a row of 45 little pairs of lights is lit on the bottom is all but impossible.
Yes, position on a vertical light. I second guess myself on horizontal lights, but it’s always (I think) red on the right side. For the most part, the shade of green used in traffic lights looks almost white to me and red looks red but it depends on the light.
But the little LED indicator lights that can be green or red or orange or “amber” (whatever that is), hell if I know. If I lined all those colors up they would all look slightly different to me, but only seeing one color at a time I’m clueless.
Yeah, my dad was red-green CB, and said the position was standard for both vert and horiz. I was going to suggest memorizing the position for your security gate, but can imagine the position/size might make that less obvious.
Dinsdale Piranha was a character in a MP skit, pursued by a giant hedgehog named Spiny Norman. You can google more info than you ever cared to know about them.
I’m not colorblind, but, to be fair, you don’t really need to in the vast majority of times because context provides plenty of information.
If traffic is going through, then the light that’s lit is the green one, and when it changes, it’s to the yellow one, and then you stop. If traffic isn’t going through, then the light that’s lit is the red one, and when it changes, it’s to the green one.
That probably gets you 99+% of traffic light interactions. And you get most of the rest by waiting for someone behind you to start honking.