Black Balloon

I was waiting for the light to turn green just outside of the parkade at work. There were no cars going either way under the tunnel but there was something travelling through, taking it's own sweet time. It was a black balloon. That's it. Just a black balloon on a string meandering through the tunnel. It was heading west. It'd get really high, to the point that I thought it would lodge itself between the beams but just before it did, it'd make it's way down again. Slowly but surely it would get lower and lower, so low in fact had there been a car around (which is highly unusual after work for there not to be any) that it would have popped it as it run it over. If you get stuck at the red light just as it turns red, you have about 3.5 minutes to wait for a green light. It was almost a full 3 minutes before any cars appeared...just that black balloon. Wonder what it meant...