Hooter - Attack - Yield
The spectre of driving on the roads of Cairo seems to have some legendary status. Not surprising, as none of the road rules of the West exist here. The most extreme example I suppose is occasional vehicles driving the wrong way on dual carriageways, at night, with no lights. (It's common during the day). We've seen this enough times to have done it ourselves, in daylight, and with a dirt verge on which we can keep out of the way. It can save a lot of extra mileage.

But there are rules, which seem to be very strictly and constantly adhered to.
Number one is to be constantly 101% alert to everything on the road, everywhere, at all times, and to how everyone else is driving. Everywhere.

Secondly, and lastly, 'mirror - signal - manoeuvre' has absolutely no meaning.
If you want to do any sort of manoeuvre, you will be constantly aware if any other vehicle around you is going to do the same thing, and thus you will constantly know when you can do it, or not.
So, if you're squeezing between lanes two and three (in a car, not necessarily a motorbike) on the four lane ring-road and you see traffic on the shoulder is going faster than you, you will know the precise moment you can cross all the other lanes to join the shoulder traffic. And at the first twitch of your vehicle, all adjacent traffic will yield to your movement, including the faster traffic on the shoulder which will let you smoothly merge. The theory seems pretty simple, but in reality it does feel a little, or maybe a lot, horrendous.

But without a doubt, when riding a motorbike, if you so much as glance in your mirror, there will be a barely-perceptible change in the course of cars alongside as they assume you are about to do something. The readiness to yield to any other vehicle's manoeuvre seems to be the key.
The corollary is that having started some cutting-in or cutting across, you're expected to complete it smartly so the yielding driver has hardly to lift his right foot.

But one thing I can't fathom is the use of the horn. It can mean 'I'm coming through', 'go ahead', 'go faster', 'hello', or even 'how's the grandson?'

In reality, there seems only one manoeuvre that is really dangerous for visitors and needs constant awareness. That is the propensity for local drivers to turn right directly from the left-most lane of the road they are leaving. So keep away from the right hand lanes near turnings on the right, otherwise a stream of cars from the left will encircle you, flying over you if they could, to reach their turning. But again, they seem to know full well you're going straight on and weave around within inches of your front wheel accordingly.

There is also one regular spectacle that goes a little way to convince us that we aren't quite mad to be riding on these roads.
There are quite a few motorbikes on the city roads, all ridden by men. But often they have a woman on the pillion, usually in full smart arabic dress, colourful with decorative head shawl. She usually sits side-saddle, chatting to the driver, oblivious to his constant Hooter-Attack-Yield weaving through the traffic. And it's not unusual to see her carrying a baby as well!

Have A Safe Journey.