It's a cause of wonder (and dismay) to many but scientists have gone out and done the hard work to figure out why women spend more time in the bathroom than men.

In general, queues for public restrooms are longer for women than for men but no one could exactly figure out why it takes women longer to come back from using the bathroom at places like restaurants, sports stadiums or concert venues.

A new study by researchers from Ghent University in Belgium has exposed the two main causes of longer bathroom queues for women.

It turns out the actual design of the bathroom has a lot to do with it. Each stall takes up more space than urinals and, as such, for the same total area, women get a loss less "usable" bathroom space. Overall, the study found, an average toilet area can have 20 to 30 per cent more toilets for men than for women (as male toilets have a mix of urinals and closed stalls). Male bathrooms, overall, can accommodate more people at any given time.

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The second reason has to do with the act of going to the toilet in itself.

Other studies have shown that women take about one and a half to two times as long in the bathroom and a lot of this has to do with practical aspects such as more doors having to be open and closed (comparing to men using urinals), and more clothes having to be taken off and put back on.

The combination of these two factors leads to longer lines, especially at busy times (like at the end of a concert, when everybody heads home).

The solution? Unisex bathrooms (which have the added bonus of being transgender-friendly and, as such, shutting down a whole other social debate).

The researchers found that moving to unisex bathrooms would cut women's waiting times from over six minutes down to less than a minute and a half.

The unisex bathroom, that researchers described as "the holy grail" should have a ratio of two stalls to one urinal, allowing men to use urinals and both genders to use the bathroom stalls.

The experts concluded this new configuration would reduce overall wait times by more than half (about 63 per cent, in fact).