had another truck do it today , pulls alongside then slows to my pace then for about two seconds goes a bit faster then slows and on and on ,whats going on if they can go faster why dont they keep going fast ,why fast ,slow, fast ,slow
seen it a fair few times lately ,is there something wrong with the truck
was it a scania by any chance?
I once had a plastic pig that did that, if you had the cruise on and were just edging up on someone then just put the gas pedal on the floor and you would get bursts of speed that helped you past.
Obviosly i was driving a tipper at the time and had to get the old erf about at 2million mph to keep the gaffer happy but yes never seen it since tho.
The old ERF EC10’s used to do it. If you pressed down the crusise control rocker switch about every five seconds, then you could get about two seconds of extra speed.
Generally, too much trouble than for what it was worth.
I was gonna ask the same question
Had a ■■■■■■ old rigid do it to me this week. 
Happens to me with what seems like every second Scania rigid I overtake…they seem to lunge forward…slow down…lunge forward etc, it gets very annoying when your overtaking but it must be a problem with the truck if so many are doing it and it does always seem to be the Scania’s.
eldor:
it must be a problem with the truck if so many are doing it and it does always seem to be the Scania’s.
Or a problem with the drivers not knowing their vehicle and it’s limitations. 
was it the old ERFs that had a mechanical limiter and the others had electronic ones? - if so. have SCANIA got hold of the old mechanical ones?
I blame the weather. Sitting on the M4 on Saturday with CC on I started catching up with the car in front As I got closer he pulled away, slowly increasing the gap, then slowed down again and so on for miles. eventually I figured out that he was slowing down for the 50mph matrix sign, then speeding up after he’d passed it, until we came to the next one. And there was I thinking the limit applied until told otherwise.
“Dabbing” the accelerator was a popular way of getting extra speed with mechanical limiters - FL10s etc. If you let the limiter subside then hit the pedal again you got a quick extra bit of speed until the limiter sussed out what you were up to. It made up for doing 10mph up the Woodhead or running out of water every time you passed Ainley Top.