An interesting observation about M 2 is that on the dividing wall their are markings for each KM done.
Travelling from lahore you can view how many km's u have made by carefully(make sure this observation is made by anyother person except driver) observing on the wall that there is distance covered mentioned in Yellow.
While coming from islamambad Distance left is mentioned.
Also i would suggest for all CNG users not to take the gas from Bhera rather take exit from bhera and try the cng which is just around the bhera exit.
Last time i tried it it had 260 presssure and the gas gave excellent mileage and perfformance despite the elevation after salt range.