Nowadays don't seem to see a lot of speed cam on the highway but beware.
Unmarked Renault Fluence and Megane (Black in colour) as Highway Patrol armed with speed gun at all highway in SG. They will follow the front car and take down the speed before pop back into the centre lane waiting for another vehicle to overtake it. Then come out again and snap your speed with their speed gun.
Spotted them twice at PIE toward Jurong and another time, CTE toward Yishun. All 3 different number plates which indicates that there are plenty of such vehicle from TP. Can easily identified, they have a very long antenna on their boot. (20 inches long). Both passenger and driver in full police uniform.
Saw also one spotted stopping a vehicle along PIE with their portable blue blinkers.