Have you ever wondered why the roofs of London's buses are white?
Right, we're just going to say this off the bat, we didn't realise the roofs weren't red and now we can't un-see it.
And, it turns out there's an incredibly intelligent reason behind the different colour roofs.
So, a Reddit user took to the social media site to share their complete shock: "London buses are white on top, how did I not know this?"
Naturally, people started offering up reasons why the roof might be a different colour.
Some said it was to do with the identification code on the top of the bus, FYI, it's not: "The black ID number probably doesn't stand out enough on red, so it's on white to be easily identifiable from a helicopter/CCTV."
Another quickly de-bunked that theory, saying: "But, that doesn't explain why the whole roof is white - they'd only need to paint the bit surrounding the ID numbers?"
One said that it was because the people ordering the buses were tight on cash, or couldn't be bothered to paint: "Maybe white paint is cheaper? Maybe it makes it really obvious the length and position of the bus from above? Painter was just a lazy sod? A combination of all the above?"
And, it'll come as no surprise that wasn't the answer either.
After a bit of digging the true reason behind the different colour roof became apparent - it's efficient.
You see, while you might be surprised by the roof colour, it turns out that the white-topped vehicles have been roaming around London since 2004.
The white roof reflects the sun, keeping the bus cool in the summer and preventing it from overheating.
While it certainly doesn't feel like it works in the middle of August when you take the 119 through south London, we appreciate the effort.
If you're wondering how this makes things more fuel efficient, it's because the bus doesn't have to use air-con, which consumes fuel. It also means that the buses are more environmentally friendly.
But, the brilliantly thought-up design doesn't just work in the summer as another Reddit user-added - the white roof was also useful in the winter: "Also since white is the slowest in emitting radiation, it helps to trap the heat during colder times, especially atop where all the warmer air naturally goes to."