When the dot matrix signs that are located on the central reservation on motorways signal the speed limit at 50mph,(or 40 or what ever), whats happens to Lorry speed limits??
Obviously cars can do 70, and they are being slowed down to 50, a drop of 20mph. Does that mean all the other limits fall by 20 too??
ie, lorrys limit falls to 40■■
If a lower posted limit is on a road than the restricted limit that applies, then you do the posted limit.
IE: Dual carriageway, goes from derestricted to 50mph. A truck doing what they’re supposed to, will carry on doing 50mph in quiet satisfaction. The same road drops to 40mph through a town, and the trucker drops to 40mph, when it returns to derestricted, he returns to doing 50mph.
Similarly: Motorway - you’re allowed to do 60mph, if a lower limit is posted, either on signs or the matrix boards, then obey that if it’s below 60, otherwise, do 60 (or as close as your limiter will allow).
If we follwed the 20mph less idea, then on a big A road through town with a 30mph limit, we’d be doing 10mph… Not exactly a sensible suggestion.
Basicly: do the limits in the highway code unless the road has a lower posted limit, if it has, then obey that. Simple eh?
Cool, Thanx alli… Just wanted to make it clear in me 'ead, tiz all… Thanx. 
Motorway matrix speed limits are “Advisory”. as are most maximum speed signs for bends. Enforceable speed limits are enclosed in a red circle.
In the highway code, it says that this is a “Temporary Maximum Speed” sign??
But I thought that this was for cars and everything else had to reduce speed by the same amount…
I’m with Krankee on this, when I did my class 2 I was told by my instructor that the matrix signs were advisory, unless enclosed in a red circle like the M25.
Amber flashing speed limits as far as I’m concerned are advisory, at least that was what I was taught.
Okay great, thanx for the replys… appreciate it guys…
Andy, I wouldn’t have thought you had experience of anything less than 100mph looking at your pic 
How about this for a motorway sign
Rob K:
Andy, I wouldn’t have thought you had experience of anything less than 100mph looking at your pic
… aint that the truth!!!
And yeah Simon, wish they would put some more signs up like that.
AndyM:
In the highway code, it says that this is a “Temporary Maximum Speed” sign??But I thought that this was for cars and everything else had to reduce speed by the same amount…
Read that again Andy! Esp. the 1st part of the sentence… you’ve answered your own question! It IS for cars, & doesn’t affect us unless under 60 on a m/way.
Regards, Jonathan
Ex. o/d Ex. LGV Instructor. DSA ADI. RoSPA Gold
Krankee:
Motorway matrix speed limits are “Advisory”. as are most maximum speed signs for bends. Enforceable speed limits are enclosed in a red circle.
correct Krankee, BUT be warned all: its not advisable to exceed by more than 10mph as its possible to be prosecuted for “driving without due care.”
I was told this by a very experienced m/way patrol officer. (in a social situation…not on the shoulder!!!)
Jonathan. Ex o/d Ex. LGV Instructor. DSA ADI. RoSPA Gold