By rule, NOC is required only if you transport your car by some carrier/truck etc. While driving it yourself, you only need to have all documents in place. No NOC required in this case. But that is by rule. I traveled from LHE to KHI and then KHI to LHE last year with family. Thulla's still tried to get me using different means but I got away without giving any bribes or any problem at all. They didn't inquire me about any NOC. However, NOC is required to send your car/bike from train/truck/loader etc. at the time of loading.
My cousins also traveled on N5 a few years back and they were asked to show NOC some 5-6 times and everytime they had to give some 200 rupees. That is just their way of looting people. One more experience is that, even if you have your car on your father's name, they'll ask you to produce Authority letter to drive from the owner. Even if you show it to them, they'll ask you to show insurance papers. And if you show them that, even then they'll ask you to show highway signs code book. If you show them all those documents they asked for, they'll try to find some flaw like you were not wearing seat belts, you have no official number plates etc. etc.
Final verdict is, You don't need NOC or even authority letter. Some policemen may or may not stop you. If they do, you are bound to show them your car's registration book and at most driving license only.
Note:- Just for the info, I needed to send my bike through train so I needed NOC. I got it from ACLC in Liaqutabad. NOC for every type of vehicle is provided from there. For that, you'll have to give some 200-500 rupees to an agent siting outside ACLC to get the form and get it filled by him. In addition to that you'll need
1. Copy of vehicle's registration book
2. Copy of YOUR CNIC
3. If car is in the name of someone else, then also take copy of his/her CNIC as well just in case
4. NOC Fees 500 for bike and 1000 for car as far as I remember, that you'll give to data entry operator without any receipt and that he'll put into his pocket directly
You may also see this link to read about one more such example.
