Last year I got 2 summons for speeding, both on the same day 6 mins apart. Turns out these were at the Ipoh NSE portion where the limit was 90km/h.

Recently travel north and paid extra attention. But I noted the road was relatively flat and smooth. Unlike the Menora section which is hilly. So why did they reduce limit to 90km/h between the Ipoh entry and exits? Amy unassuming driver like me wouldn't have realised the limit reduced to 90km/h unless pay extra attention to the signs as the terrain is normal.

Means you're young loh.

Last time, the NSE stretch between Ipoh South & Jelapang wasn't like this.

All vehicles kena pay for exit at Ipoh South, then angkat tiket again at Jelapang. Means the Ipoh South to Jelapang stretch was not a closed highway, and is toll-free.

The speed limit of 90km/h was set during that time.

can know the exact km number on your saman?

Finally, a proper answer.

Why retain the limit though when it's now a full blown highway? And why set speeding traps at 90kmh in that stretch?

Because you don't pay toll for that stretch of road.