How does that work? ... and strange colors!

I was at the Walmart in Hemet last week and noticed this warning on the shopping cart:

 Attention shoppers

Our shopping carts will lock if taken beyond our parking lot boundary. The boundary is marked by a series of special yellow lines.

How does that work?

Is there some magnetic field that causes the wheels to stop turning?

By the time I got to the parking lot, I forgot to look for the "special yellow lines" because I was so surprised by the color of the Jeep. 

When I got to where I had parked the Jeep, I was wondering if this was, indeed, our Jeep. It looked like a black or deep purple color (instead of its normal red).

The lights in the parking lot were yellow. My friend, Joe, had told us that a lot of the lights are special colors to help with night sky visibility at observatories.

Given that the lines that mark the boundary of the parking lot for the carts are "special yellow lines", and given that everything looks yellow in the evening, I probably could not have found the "special yellow lines" had I thought to look for them. But... I have to say, since I came across the picture I took of the warning on the carts, I want to go back and try to take a cart off the lot to see what happens!!!

<<< I had written the above blog post to post and... then it turned out that Dwayne and I went back to the Walmart during the day a couple of days ago... so... this is the "rest of the story".

I dropped Dwayne off and he went in the store... I located a cart near the edge of the parking lot, and when I picked him up and explained the sign that I had seen, he was likewise wondering, "How does it do that?!?!?"

So, we drove to the cart that was near the edge...

We noticed that one of the front wheels looked "different" (the one on the right).

We also found the "yellow line" though, I have to say, it was not very yellow! Maybe if we were there at night when the yellow lights are on???

 So, we pushed the cart over the line, and initially, nothing happened... then, that front wheel locked up! We couldn't push the cart any further....

We lifted that corner of the cart off the ground and brought it back to the "safe" side of the yellow line, but... it didn't unlock! I guess the cart handlers must have some sort of key that goes into that slot and unlocks it so it will roll again. I had planned to walk the cart back to the store (rather than leaving it out at the edge of the lot) after our experiment, but since it no longer rolled very easily, we left it out near an island in the parking lot and felt guilty for causing the cart handler additional work!

So, now you know, and you don't have to try it at *your* local Walmart!