There are some things you should know about traffic in Jordan, particularly Amman.
Lanes are overrated.
Most of the time you won't be able to see the lanes on the streets because there a) aren't any lines or b) they have faded and nobody bothered to redo them.
But even where you can see them it's best if they stay ignored. Because that's what everybody else does and adjusting to the others - driving four lane style where only three lanes are - is much easier when you don't stick to your lane.
Signaling is overrated.
More than half the time, the person in front of you will take a left or right turn without telling you so. You will know when you suddenly see their rear lights going up, you need to brake and somehow avoid that the person behind you drives into you.
I have taken a special hating to people doing this. Because it happens all the time. Sometimes, while you wait at a red traffic light, a car will drive up next to your right side and signal. It's as if the driver was saying: "I am a rude prick who doesn't give a shit about you, now, please let me in before you?"
Accidents ruin everything.
Oh yes, you think, same here. Traffic accidents are always annoying and never pleasant. But there is a catch. In Jordan (it can't be just Amman can it?) people often remain at the spot where the accident happened. To save the proof or whatever. And because it's easier on them this way, considering that there is never an empty space around in which to bring your vehicle while you wait for the traffic police (which, not uncommon, might take an hour, maybe more). Ammani streets, though, have no space to accommodate such situations. It inevitable turns into a traffic jam mess because nobody wants to let the other in but wants to be the first person out of it.
(Often, you will find a police man next to the hit car in the middle of the street whose being there is unclear and who behaves completely useless.)
Your horn is a valuable weapon.
Use it where you can, when you can. To signal somebody to move out of your way, to tell somebody that s/he should pay attention to others on the street, to voice your anger over somebody's style of driving.
Don't ever make space for others.
When you drive around, make sure you always stick to the car in front of you. Do not leave space. As soon as the gap is big enough for another car, it will be filled. Everybody is always in a hurry, always trying to rush through the streets. Your personal goal is to be close enough to the car in front of you to make sure you don't do any favors but at the same time leave enough space to allow to brake when the car you're creeping up to suddenly decides to brake.
Park wherever you want, however you want.
This one might not be very convincing without pictures, but let me tell you: Ammanis are the worst car parkers I have ever seen. Diagonal on two spots, unable to accomplish parallel parking, occupying half (or more) sidewalk with your big ass vehicle. And come to think of it, it's not all that surprising, at least for those in West Amman. Most shops, restaurants, malls have valet - if you don't want the hassle, pay one JD and you don't have to worry.
Ignore signs. Especially Stop and No Entry signs.
Drive wrong way into a one way street! And then use your horn if the person coming from the other (the right!) direction doesn't want to give you way. Drive past stop signs without stopping, ignore priority signs, they're for the weak.
Pedestrians are your enemy.
I do have some sympathy for pedestrians having walked around this city (or tried) in the past. There aren't a lot of pedestrian crossings or proper ways to cross a street. They aren't proper sidewalks how could anyone expect there to be proper behavior towards pedestrians?
The safest way to cross a street in Amman is, indisputable, a pedestrian bridge. What is infuriating: Those pedestrians close to the bridges trying to cross 6 lane highways (or whatever number of cars try to drive next to each other). They always seem a little suicidal.
When you think you can finally speed, there will be a bumper.
You are always in a hurry, always late for something, never on time and there are hundreds of people around you facing the same issue. When you finally knocked everyone out and see yourself facing an empty patch of street on which to break the speed limit, there will be a bumper. They are everywhere. And they are there for a reason, I believe. (You don't really believe anybody cares for the speed limit within cities? Where I come from you have to slow down in residential areas, not so here.)
Instead of having a reliable, accountable police force giving you speeding tickets, the government puts up bumpers to make you slow down. They will be where you least expect it.
Forget what you've learned about the rules of driving and pretend you're alone on the streets. Then you'll be able to imagine what driving here is like.
Beware, although you try everything to be as fast as possible when driving around (horn, as little distance as possible, as many lanes as will fit on the street, furious road rage) you will, inevitably, be stuck in traffic. There is no way out of it. Modern Amman, although no more than 100 years old, is a big example for horrible urban planning, lack of foresight and accommodating the ever growing number of vehicles on the streets.