Although seeing Iran by  your own car is absolutely the best way to get around, getting it in-  and out is definetely not for the faint of heart...
The condition of the roads is fine, traffic is chaotic and petrol is  cheap. Most importantly, you can go anywhere you want, anytime you want.  Car rental is an unknown concept in Iran.
About the traffic:
Initially, is seems like complete chaos, with all drivers taking the  shortest line to wherever they want to go, swerving across lanes and  going on roundabouts in all posible directions. However, there is  actually a system behind the apparent chaos, evident by the fact most  cars are not dented. Here it is: "Whenever two vehicles collide, the one  with the damage most towards the car's front is responsible."
This means anyone can cut into your lane, leaving you liable if  he/she hits you.... So you brake.... to avoid your car's headlights  touching the other car's side... On the other hand, the advantage of the  system is that it is very easy to get across lanes when you find  yourself on the wrong side, just metres before the junction; You just go  and all drivers will let you cut-in without any honking protest, even  buses or trucks.
On roundabouts, it seems the priority is for those entering it but  just like for the motorbikes buzzing around you everywhere, you make  judgment if you are good to go and just go. Everyone is very focused on  avoiding to hit anything with the front of their vehicle, particularly  since many are uninsured....
Do not drive outside town at night! 
Now for the paperwork:
Main rule; Be mentally prepared that it will take significant time and  effort. 1 - 2 days on arrival and 1/2 day on departure is not uncommon.  Don't try to do it all by yourself. You need help from someone who knows  the system, how to butt into lines and who speaks Farsi as well as some  English to communicate with yourself. As foreign tourist you will be  treated very friendly with the utmost regard.  (Surprisingly, Iranian  nationals not so....).
To get help, a good start is 
Samira Zare from  
Persiatours, who is making study of the process and has useful contacts  that can help out in most places. These will need some payment, but it  is worth it. (several tens of euros, depending on how quickly it goes).  The whole process involves many rather small payments everywhere, that  amount to a few hundred euros total.
To have before departing:
1. 
Carnet de Passage en Douane: Must have. The alternative is having  to leave a huge deposit at customs (tens of thousands of euros), which  is not only very difficult to pay through a state bank, it is also not  clear if you will ever get it back after departure, especially if you  enter and exit at different border crossings. You can get the Carnet  from the main  motoring association in the country where your car is  registered. (For NL cars, the ANWB has an arrangement with ADAC). The  huge deposit still applies, but now you have certainty you will see it  back, after returing the properly stamped Carnet at the end of the  journey. Be aware that in different places, the Carnet often comes under  different names (e.g. Triptique, KT)
2. Export license: If (like us) you are taking a foreign car back to  home country, this is a particularly bad proposition. It means you will  be literally exporting and importing the car at every border crossing,  which will take 4 hrs to 2 days at every border. Keep the regular  registration (and your local residency permit to have it legally in your  name). Do get a Clearance Certificate from the Traffic Department which  you will most likely need when registering the car in your home  country, but do check your home countries regulations for import.
3. Road insurances: Try to have these arranged for all countries  beforehand. Samira of Persiatours can help you get it for Iran, if your  own green card does not cover. The challenge is that Iranian insurers  only give "normal" rates to drivers with valid Iranian civil ID, which  as tourist you will obviously not have. Unlike other countries, Iranian  border crossings do not have agents with "Border Insurance". In our  case, after getting and offer with a staggering rip-off rate, we managed  to charm another agent into buying the insurance in his own name, which  consumed over 4 hours.
4. Visa: Must have
5. Ferry tickets: For Sharjah - Bandar Abbas, Oasis (local and only  UAE agent for Valfajr8 shipping co. and currently in process of renaming  itself into Goodluck shipping co.) needs copies of the Carnet,  passports, ownership certificate and visa. There is another shipping  agent for the line Kuwait city - Bushehr, but Oasis was the only one  willing to make a reservation by email. The actual ticketing in Sharjah  takes one day (before departure).
6. Lots of copies: Make at at least 10 sets of copies of passport (ID  page) and visa, as well as a few sets of your other docs. These save a  lot of time.
7. Itinerary: Plot your planned itinerary on a print-out of Google  maps. This helps a lot to give the authorities the confidence that you  are really planning to bring your car out again, rather than sell it in  Iran, dodging their massive taxation on foreign cars.
8. Folders (preferably transparent plastic ones) to keep your  precious papers organized and prevent from blowing away with the wind.
9. Tools to change licence plates and make holes in new ones.
The Ferry:
1. The folks at Oasis will help you through the process excellently.  Arrive one day before to purchase the actual tickets and have cash  Dirhams, original Carnet, Ownership certificate and passports/visa.  Oasis agency is inside Port Khalid and very hard to find without GPS and  coordinates. It is an unmarked portacabin with three offices inside.
To  get inside Port Khalid, you will need a gate pass, which you can get at  the gate pass office. The gate pass clerk will claim Oasis'  (Goodluck's) agency is outside the Port, but this is not true. Gate pass  costs 5 Dirhams and a passport copy. Oasis is planning to open a new  office in town, but not clear if/when that will actually happen. Do  regularly check if the ferry is still scheduled to go. Due to low demand  or military exercises in spring, there may be cancellations.... Buying  the tickets takes about one hour and they will keep your Carnet and  Ownership certificate.
With the now received Bill of Lading, you go into the Port Authority  building, right-hand side after the front door and within 5 minutes they  give you the Vehicle Admittance Advice (4 different colored copies)  after showing your Bill of Lading. Be on time. The Port Authority closes  shop at 14:00. No cost. Done for the day. Behind the scenes Oasis takes  care of some more formalities.
2. Next (departure) day, you arrive at 15:00, drop other passengers at the  airconditioned Port Authority building and then go with the car first to  Oasis, then to Customs shed #6. Have all papers with you, some will be  retained, stamped and/or signed. You leave the car there and if not  comfortable with their driving skills, you are allowed to keep the key.  You will be brought to the gate (in one of the other cars they do have a  key of) and reunite with the rest of the travel party.
Now you can enter the "Departure hall" and after paying the guy in  the office left in the back he will take 30 Dirhams for each passenger  (no receipt) and issue the "boarding passes". Also your original Carnet  and Ownership magically pop-up there and are returned to you. Take some  time to marvel at the place and the huge amounts of freight people take  with them to Iran, which are mostly their reason to go by ferry, rather  than by plane.
The next interesting scene is the waiting of the entire and colorful  population of the ferry at immigration, passports getting exit stamped  one by one, then everyone loaded into a rattling Tata bus for the 400m  to the ferry, which is patiently  waiting next to the Oasis office.  Somewhere halfway all this you get a call and are collected to park your  car on the ferry, then brought back.
3. On the ferry: Enjoy the ride. Departs around 21:30 and you will be  served your first Iranian grub. Sleeping is basic on hard couches, but  get some rest. You're going to need it.
Port Khalid
    Gate pass office.                  N25 21' 24" E55 22' 29"
    Main gate.                           N25 21' 34" E55 22' 37"
    Port authority building.         N25 21' 31" E55 22' 34"
    Departure hall.                     N25 21' 35" E55 22' 34"
    Customs shed# 6.                N25 21' 43" E55 22' 32"
Oasis shipping co.
    Mr. Naser.                          +971 50 786 8280
    Mr. Imran.                          +971 50 470 6830
    Office.                                 N25 21' 49" E55 22' 35"
    Ferry berth.                         N25 21' 49" E55 22' 32"
On arrival.
1. Just before docking, the ladies have to put on their headscarfs  & long-sleeve butt covering blouses and notice the smiles and sighs  of relief from the other passengers. On disembarkment around 09:00, the  car key stays with the ferry's shipper.
2. First through immigration. Men and women separate lines, but soon  enough the officials call the whole family forward and you skip the  line.
3. Now you have to go to South Way Shipping co, some two km outside  Port Bahogan to make a payment for their destination handling and get  back. This is a good time to first find a local fixer to guide you  through the whole process of getting your car released from the Port,  before Customs closes at 14:30.
This process involves visiting a large  number of offices all across the port to collect a mindboggling   plethora of papers, stamps and signatures.
Your role is to be the  foreigner that enables the fixer to jump queues and interrupt officials  in their lunches. If things are getting a little late, some running is  also involved, but colleagues of the fixer also pop-up everywhere with  cars to cover distances quicker.
Worst case is a taxi to your hotel and  finish the process next day. Not a bad idea to send the travel party off  to the hotel anyway, since there is nothing to do for them, but wait.  Taxis are plenty available at the Port gate and cheap. Have a flexible  reservation with Hotel Hormoz, if you can afford. Other hotels in B/A  are no great deal. The process always works out in the end but how long  it takes is unpredictable.
Port Shahid Bahonar (Bandar Abbas)
    Ferry berth.                    N27 09' 11" E56 12' 13"
    Main gate.                      N27 09' 17" E56 12' 25"
    Customs.                        N27 09' 15" E56 12' 18"  (here are the fixers)
    South Way Shipping co. N27 09' 57" E56 13' 42"
Transit plates, the day after arrival.
Required if you are stay in more than 7 (some say 15) days, although  the actual law is not clear with everyone.
Basically very simple: Make a  tax payment at the state bank accross from hotel Hormoz and have  insurance. With that, you can show-up at the Traffic Police side gate at  09:00, 11:00 or 13:30 for inspection and receive the transit plates.  Again, as foreigner you will be treated with greatest respect and  priority. To show your planned itinerary plotted on Google maps really  helps here to get the Police's confidence.
For the tax payment, you will still need the fixer. The state bank is  the most mindboggling bureaucratice monstrum you have ever seen. It  consists of five floors of offices with people behind desks, receiving  or issuing slips of papers, stamps and signatures, five cashier sub  banks and locals streaming through corridors, up and down stairs and  mostly elbowing at the desks. After a couple of hours, you have seen  every corner of this miracle of inefficiency and walk out with the  needed receipt. Good chance to observe the local dress.
For the insurance, refer to above in this article or be prepared for hardship and desperate negotiation...
Once you are given the plates and the license registration slip, the  guy at the kiosk near Traffic has all the equipment to change the plates  for a small fee, unless if you brought these yourself, which will be  much quicker....   DONE! Free to go!!!
Traffic Police.                       N27 11' 12" E56 19' 51" (inspection gate)
                                            N27 11' 14" E56 19' 55" (main gate)
Hotel Hormoz.                     N27 10' 59" E56 17' 26"
|  | 
| Thijs at Traffic Police in Bandar Abbas-Iran | 
Exiting Iran is much quicker, but you will still need a fixer who  knows who is who at the border. Plenty will approach you. Take some time  to pick a good looking one that speaks some English. At Bazargan and  likely all land borders, the Iranian side is a complete mess, with  people pushing and shoving to get across, overworked and rude officials  (none wearing uniforms) making up rules on the spot.
For example, one  guy noted that our transit plates were issued in Bandar Abbas and ruled  that these should be handed-in there too. Go figure... After a while the  conclusion was that Traffic Police at Khoy, 160 km back was the right  place to go, but after some convincing that all our visas were already  voided with exit stamp, he finally put the indispensible exit stamp on  the Carnet and the plates were dumped in a bin that contained many  more...
After a few more inspections, the gates of Iran and Turkey opened and  a few formalities later on our way to Van. Visa cost USD 20 (TL 35) and  3-months insurance for Eastern Turkey available at the AXA office (same  hall as the visa window) for TL 50 in 10 minutes only. Welcome back to  civilization!
Thijs Broekhuijsen