Even in cities whose populations are in the millions and hundreds of thousands, you never quite know who you might bump into when you're out and about.
"Fancy meeting you again after all this time".
Unfortunately by 'bump', I literally do mean bump.
These days, hardly anyone looks where they're going. And what's the reason for this new collision culture? Is it because of what's on our minds or rather more to do with what's in our hands? Apparently, the masses can't stop staring at their phones.
They're strolling along the street texting, emailing, instant messaging and calling. "I haven't heard from you for ages (three minutes actually). Anyway, I thought something might be wrong and that you were despeerately trying to reach me".
The last thing the nation's men, women and children are doing is concentrating on who or what is in front of them. They walk straight into the path of fellow pedestrians. You can see them coming. But they can't see you. It's as if you're invisible. Bloody great. No one notices you at work (lately, all your efforts seem to have been to no avail), now no one notices you outside of the office either.
Maybe you need to wear more outlandish clothes. Something from the Jean Paul Gaultier SS14 collection. Alternatively, try going naked. Surely that will get you bring you to someone's attention. Yes, probably the police. "Excuse me Sir, but you appear to have forgotten to get dressed this morning".
The problem is that the public are increasingly becoming technology slaves. They're clinically unable to stop checking who, in a matter of life of death, is wanting to get hold of them. Invariably, it's only British Gas offering to put them on a better tariff or another firm of ambulance chasing lawyers offering them compensation for the open man hole they're shortly about to plunge into if they're not more observant.
"Oh, I'm so sorry", you find yourself saying, as they smash straight into your being. Hold on, what the heck are you the one apologising for? They're the ones to blame.
What you really should be saying is: "Jesus, for once can't you do without that infernal contraption?"
You should then proceed to prise it out of their vice like grip and jump up and down on it before their very eyes, eventually handing it back to them and uttering the words: "Oops, I think it's just gone to voicemail".
Of course, it wouldn't be quite so bad if this preoccupation of staying in touch with each other was restricted to the pavement. But it's not. It also extends to the road, where things can get really dangerous.
People step from the kerb in the midst of another missive only to be confronted by the screeching brakes, blaring hooter and angry screams from an oncoming motorist who only manages to stop hitting them with millimetres to spare.
Not that said motorists are such an innocent bunch when it comes to the use of mobile devices. It's illegal to use a hand held phone when driving or while stationary with the engine switched on. The fine can be anything up to £2500.
From the amount of folk I see flagrantly disregarding this law, I'm not sure such a fine is much of a deterrent.
As a cyclist, I've lost count of the amount of times I've ridden past a car only to see the driver merrily chatting away on their handset.
If only I knew their number, I'd text to tell them that they were endangering the lives of other road users, particularly yours flamin' truly.
The fact of the matter is that there are very few occasions when the use of a mobile phone can't be avoided for a short while.
Certainly it would increase safety and allow us all to start appreciating the surrounding world from a little higher than a few feet.
Instead of looking down the whole time, we could be looking up. Behold the blue sky, the white fluffy clouds, the soaring birds, the wonderful gothic architecture.
Heavens! get a load of those of those magnificent gargoyles. You really must take a picture of them.
"Yeah, well, perhaps I would if only I hadn't been successfully persuaded to leave my phone- with its 12 megapixel camera- at home for the day".