Harriet Green usually drives the car and her husband is the passenger. This is rare – in most couples the man takes the wheel. It's a touchy subject, but is it about gender or an individual's need for control?

We were giving a lift to the 12-year-old daughter of an old friend. My husband was in the passenger seat and I, as usual, was at the wheel. The 12 year old seemed genuinely perplexed by what she saw as a risqué reversal of gender roles. "Why isn't he driving?" she asked.

It's worth noting that her mother happens to be the family's main breadwinner and is an alpha woman in all other respects – but not, it seems, when it comes to the car. Driving the family around is her husband's domain.

It set me thinking – and looking. In the majority of cases, I noted, when couples were together in cars (with or without children), the man was driving. There were plenty of women driving on their own – to work, ferrying the kids around – but once coupledom came into the equation, some sort of 1950s model seemed to take over.

This is borne out by statistics. The Institute of Advanced Motorists (IAM) did a survey in 2010. It found that when partners drive together, men are four times more likely to take the wheel. Women drivers are more likely to feel uncomfortable driving when their partner is in the passenger seat.

In 2009, a University of Washington sociologist, Pepper Schwartz, reported that in nine out of 10 households that identify themselves as "feminist", the man did most of the driving when both partners were in the car.

And in most car ads, the man drives.

The one time women drive more than men is when they go out in the evening. In that case, the IAM found, more women drive so their partner can drink.

I grew up in the countryside. If you live five miles from the nearest anything, you're reliant on your parents for lifts unless you learn fast. I passed my test first time at 18 and never looked back. My Renault 5 came with me to university where I ended up taxiing my friends around. My boyfriend didn't drive and was happy to accept my lifts. He was still traumatised by the driving lesson he had at 17 when the teacher told him to stop his car: "Get out, sonny, I don't want to risk my life any more." So I always had the upper hand. But, kindly as I am, I introduced him to my lovely driving teacher and my husband (as he later became) eventually passed his test.

The Renault 5 was mine and I did the driving. It wasn't until we bought a car together a few years later (well, I paid for it, but I'm generous) that he got to use the keys. Just not that often. Motorways, after all, are scary places and need an expert at the wheel.

Now to be fair to John-Paul, many years have passed and he can drive fine (even on motorways and abroad). In fact, our daughter, theoretically on my side, says he is a good driver when I'm not in the car – and quite fast. But I'm better. I love driving. I get a kick out of perfect gear changes and overtaking people and navigating country lanes. John-Paul is much happier on his fold-up Brompton bike.

I also hate being driven. I get car sick (particularly when John-Paul lurches) and he's a better map reader, so our division of labour has always made sense. It's an arrangement that we've never considered unusual until that child got into our car.

Outraged by her comments (this is the next generation of women!) I thought I'd subject John-Paul to a test. A little unfair – vindictive, even – as he's never insisted on driving, is happy to play the passive role in our vehicular relationship and I have far more road miles under my belt.

But I'm mean like that. I called Peter Rodger, the chief examiner of the IAM, and suggested he assess each of us and give his verdict.

Bravely, John-Paul went first. He was out for an hour and returned looking cheerful enough, then left to pick up our daughter from school (on his bike). Then it was my turn. I confidently got into the car and took off the handbrake before turning the key. It was something I've never done before. Hubris? Nerves? A bit of both? No matter, my brilliance would soon shine through.

Harriet and John-Paul both had their driving skills tested by the chief examiner of the Institute of Advanced Motorists. But how did they do? Photograph: Sarah Lee for the Guardian

So off we drove, Peter and me, to the wilds of north London. We negotiated mini roundabouts and dual carriageways and countryish lanes. I was excited to drive past the home of a favourite uncle long dead and told Peter all about him. I thought I was doing brilliantly. I can chat and drive and concentrate – all at the same time! I finished off with a storming parallel park in the tightest space I could find.

Perfect.

Peter smiles a lot and tells funny jokes. But he's also a former police driving examiner. Foolish me to let his good cop manner outwit me. Underneath, the man is ruthless. He sat down, smiled, then uttered the devastating words:

"How many speeding tickets did you actually want? Three enough?" In one case, he told me gleefully, I was going so fast as to disqualify me from the speeding retraining course, which can get you off a ticket.

Then, on to my personality as a driver: "You're a pushy, somewhat aggressive driver. For example, that man you called a lunatic was actually in his 70s driving a Vauxhall Zafira and just going a bit slowly."

I don't look ahead, don't plan. I gesticulate too much when I'm talking and look at the passenger when I'm doing so rather than at the road. I'm also clumsy-footed. "Every time you lifted your foot off the brake, it went clunk."

The smirk disappeared from my face. This wasn't good.

So I changed the subject. "Peter, let's get on to John-Paul."

"He's more cautious than you. And he's somewhat unstructured."

Excellent!

"But I'd probably need to intervene less quickly with him than I would with you."

Peter allocated points to our performance, using a sheet of key measures. I added them up. A high score in this case is worse. I got 41. And John-Paul got ... 42.

Whoop-de-doo! I won! Only by a point, but a win's a win!

Before he left, Peter had one more grenade to lob at both of us. We are both averagely OK drivers, in the great rump of "nothing special" but not awful either. But I take some comfort from his suggestion that I would possibly be easier to train to IAM standards than my husband (if I could keep my pushiness under control).

Why do women tend to take the passenger seat? I can't help feeling there's something worryingly passive about being driven around. When you drive, you're in control. My husband might say "Take the road on the left", but if I'm at the wheel I can wilfully ignore him and turn right. Ha! ("So you have some kind of psychological problem with ceding control," John-Paul says, very annoyingly.)

It's a touchy subject to bring up with friends but it seems that everyone has their own perfectly reasonable explanation.

Peter Rodger says he always takes the wheel, partly because of his job and because the company car is his, but mostly because his wife doesn't enjoy driving. He says he'd love her to share long car journeys.

One of my friends says his partner doesn't drive because she had a bad accident as a child and it's put her off. Another that his wife grew up in London and has always lived there, so driving has never been a big deal.

But how to explain the statistical difference between men and women? Frankly, I don't have the answers. But maybe it's time for someone to do a thorough study.

It's not just me asking. The internet is peppered with questions such as these: "Nine times out of 10 when you look at a family in a car, the man is driving, the woman next to him in the front seat and the kids are in the back. Why do men almost always seem to be the drivers?'

The questions attract answers such as these: "It's because we women are lazy, women need to keep an eye on the kids in the back, and most women would be too busy looking into the mirror to see if their makeup's smudged."

Amanda Marcotte, a columnist for the online magazine Slate's Double X, says: "Letting women take control is considered emasculating in our culture and even pro-feminist men are not immune."

"Yes, so what a treasure you have in me," says John-Paul.

There is one theory that has some support among women, but I'm not sure I want to believe it. This comes down to the fact that boys like toys. The car is the ultimate gadget and women just don't care that much – the implication being that women are simply much more mature than men. So what does that say about me?