There is always lots of traffic. The rules are simple: if you are even a fraction of an inch ahead of another car, you have the right of way. In the far right lane and need to turn left? Mafeesh Mouskela (no problem)! Did you miss your turn on a one-way street? Mafeesh mouskela! Need to park but there's no space? Mafeesh mouskela? Traffic lights? Merely suggestions, not need to mind them. Just don't use your headlights at night. It is wasteful and really annoys people. I didn't drive in Egypt because I didn't have a car, but those who did said it was like navigating a crowded sidewalk, that you do it by feel. Many people find it fun after awhile.
It only takes the ride fromthe airport to find the humor in this sign. Egyptians use the horn constantly. They honk as they go past pedestrians to tell pedestrians they are not going to stop. They honk going through intersections to tell other cars they are not going to stop. They honk when pulling a maneuver like turning left from the far right lane. They honk when someone else pulls a maneuver like turning left from the far right lane. And about every 30 seconds for good measure.