Rightly said scorpio.
BTW do you know that the official speed limit for National Highways in India is 70kmph and now for the Golden Quadrilateral stretches/Expressways it is 80kmph? For Mumbai Pune Expressway where you have six lane access controlled carriageway the speed limit is only 80 kmph.
So even if we have access controlled Expways you cannot drive fast with peace of mind, because of the fear of Radar/Interceptors.
Last Sunday I had gone for a drive in the Bangalore-Hyderabad highway. Till Devanahally, some 40km distance where it is a fully developed 6 lane stretch, (of course with lot of signals), I was lifting my foot from accelarator most times so as keep the speed within the limit. Interceptors were there and they flagged down a scorpio which over took from the 2nd lane (I was in third speed lane with 80kph limit, the 2nd lane they have kept 60 as the limit.)
To reach Kochi in 2 hours, the average speed should be 100kph. That means the cruising speed should be around 140 kph, which is not practical.
I have done several TVM-Kochi trips in 3.5 hours, early morning drives. Even the road is four laned, there would not be much difference in the timings. But you have more risk as many, esp trucks, autos etc would come in your lane, against you, to avoid travelling extra distance to take a U turn. And some bugger will suddenly appear from the gap in the medians.
Perhaps you would be able to keep higher average speeds in some two lane sections with less traffic, when compared with four lane main highways. One example is the drive from Madurai to Trivandrum. It is a pain driving through Nagercoil-Tiirunelveli-Thirumangalam-Madurai', esp in night drives. Once I was much pestered by the trucks and night running volvos. Return drive afte r20 km from Madurai, at Thirumangalam, I turned right and drove via NH 208-Rajapalayam-Srivilliputhur-Tenkasi-Shencottah-Kulathupuzha-Anchal-Ayoor-Trivandrum. Till Tenkasi, it was a bliss, practically no traffic, slightly winding well laid two lane road, where you can cruise at 90-100kph for long time.
Same was the case with Kuduru (off Bangalore-Hyderabad highway, about 100 kms from BLR) to Dharmavaram (some 45 kms) which I drove last week. I was able to keep 80+ touching 100-110 kph for most time, which I was not able to do in the four lane strech to Devanahally