Amy Poehler is an uncofirmed single-preson right now. Also she's wearing green at this Oscar's after-party which gives this image a tenous link to Dom's story.

Amy Poehler is an unconfirmed single-person right now. Also she's wearing green at this Oscar's after-party which gives this image a tenous link to Dom's story. Photo: Larry Busacca/VF13

You know what the greatest social event of all time is? A traffic light party.

I'd better qualify that, hadn't I? I mean the greatest social event of all time for single people. Who are the only people that matter at social events, in my opinion – couples only go to those things to lord it over everyone else, as far as I can tell. And then the joke's on them, because then they tend to get pregnant and never socialise again, except for those nightmarish but mercifully short toddler birthday parties they insist on throwing. (Although I've noticed I don't get invited to so many of those since I wrote about them. Funny, that.)

Anyway, traffic light parties are amazing for one simple reason: you can tell who's single. Single people dress in green to indicate they're available, coupled-up types go in red and anybody who attends a traffic light party in orange deserves to be ejected instantly. Honestly, it's even lamer than setting your Facebook relationship status to "it's complicated". Nobody cares about your tedious psychodramas.

Traffic light parties are great because ... OK, they're not actually great. They're usually conducted in one's early 20s and therefore embarrassing, so everyone gets too drunk and it's ultimately entirely horrible.

But there's a broader point here. We badly need a system for ascertaining whether people we meet are in relationships. It used to be easy, when people wore wedding and engagement rings, and tended not to cohabit before getting engaged.

Sure, just about every other aspect of those systems for relationships were demonstrably inferior to what we have today – but at least when there's a ring on it, you know not to waste your time. (Or, I suppose, to go for it, if infidelity is your thing – I'm trying not to be judgmental here.)

Otherwise, what happens at parties is this. We approach people who seem appealing, try chatting to them, but not in a way that explicitly counts as flirting in case they happen to be in a relationship.

We never go right out and ask whether they're single, because that's embarrassing too, so instead we just converse about any old thing in the hope that they'll mention a girlfriend or boyfriend if they have one. Nor will they go right out and say “I'm single”, because that's embarrassing too. Later on, if you're really lucky, you can ask a mutual friend if they're available. Wouldn't it be better if they had a ring?

Over the years, I've developed an almost uncanny ability to home in on the unavailable women at a party. Honestly, it's almost as though I have extra-sensory perception – or perhaps it's just that women suddenly invent imaginary boyfriends if they suspect I might be interested?

On more than one occasion I've spent more than an hour – an hour – talking to women before they subtly mentioned their husband, or child, or on occasion, both.

Admittedly, some of these people have subsequently become good friends, and that's fine, and perhaps I wouldn't have even started talking to them if I'd known they were unavailable, and instead opted to talk to a single woman who might ultimately rejected me, and it's better off that I've gained wonderful friends through this process.

But couldn't the system be a bit less ambiguous?

I don't give Facebook credit for much besides excellence in ongoing privacy abrogation, but they did try to sort this out in their early days. You can set your status to single, married, engaged, in a relationship, or the self-involved "it's complicated". There's a "widowed" too, distressingly.

But here's the thing – single people don't use the system. Because it's embarrassing to admit to being needy, and we'd like to pretend that we have all sorts of intrigues going on when really we don't.

Maybe traffic light parties do have some merit – because they encourage honesty, wrapped up in the idea that it's all in good fun because it's fancy dress. Of course it's not fun, by the way. If you've been single for a while, going out and trying to meet people becomes a matter of steely single-mindedness.

So it's in this spirit that I welcome the news that Prague is considering setting up special train carriages for single people. It would mean you could have a traffic light party on the way to work, every single day! And it'd be so easy to start a conversation – in Australia, anyway. You could just talk about how late the train was and how horrible the carriage is. Simple!

Actually, the idea's creepy, isn't it? When I commute, I just want to listen to music and read. And besides, Australians don't tend to chat up random strangers. And it may, of course, lead to the kind of sexual harassment that has prompted some Japanese cities to introduce special women-only carriages. Because a significant proportion of men are terrible, and so forth.

In retrospect, traffic light parties are a terrible idea – I've just forgotten because I haven't been to one in about a decade and a half. They certainly seem worse the more I think about them. And they don't account for same-sex relationships either, which probably need a whole separate colour scheme. I got asked if I was gay at a party on Saturday night, and there I was thinking my poor dress sense made the answer perfectly clear.

We aren't likely to broaden the system of ring-wearing to anyone in a relationship – which would make life easier (and besides, gay marriage seems to be some years away, Kevin Rudd's recent conversion notwithstanding) – so instead we're stuck with the system society has devised, in which you simply have to talk to people at great length and hope they'll mention a significant other, if they have one.