i am assuning you travel rarely on mway. Every beat on mway has a speed checking camera now. And they have it since a couple of years now. you are lucky to have not seen so many speed cameras before.
Earlier on, the speed limit relaxation was 129km but it has been revised coz mway police is not being given the budget they need. Majority cars need to be replaced as per theor policy but they have no money.
They never jump infront of a car. Thats da reason many people run away. What they do is, the inform the patrol unit ahead of them with the number, make and color of the car. There must have been some other case when you saw them blocking the road as mway police also helps in recovering lost/stolen vehicles and stops smuggling of different items as well.
The limit is even less than 70 at most places. The slope where they stand with the camera has 70km limit and the board is there just before the bridge starts, before the slope. you missed it
people in Pak dont know how to drive mate. You are driving at 200km with the lights flashing to let other drivers know to give you space but suddenly, a cuore/cultus or any other car driving at a speed of 100km gives an indicator and comes right in front of you. No matter what you do, the other car driver will take 2 minutes to over take a car which is going at 105km (a little faster than him actually) and wont give you space coz he thinks his action is justified as he has given da indicator 120km is more than enough for us yet where people obtain driving licenses sitting at their homes, thanks to Quaid e Azam.
Trust me, I have seen accidents happening where a car going in front suddenly changes lane and the car behind it goes right into the next car. Most of the times, left fenders are damaged.
There are different speed limits in salt range.
The have devised a new strategy to tackle the over speeding problem of commercial vehicles. Their time is noted when entering from islamabad toll plaza, for example. They report at Kallar Kahar service area. The time consumed should not be less than 1 hours and 30 minutes for busses and vans. Next check is right after salt range and it shouldnt be less than 25 minutes. There are a f couple more checks till lahore.
Same works for other destinations as well.
It has been done to stop the increasing ratio of accidents.