Smart Motorways & Variable Speed Limit Confusion

[jerrin91]

With Variable speed camera's and variable speed limits popping up everywhere especially, I believe gone are the days of following fixed and consistent traffic rules


I am yet to drive on so called 'smart motorways' but reading about the idea of smart motorways gotten me very confused on three areas:


Suppose you are following the National speed limit of 70mph with a gantry up ahead and it suddenly displays Max. Speed limit of 50mph, what woud happen if i kept going past it at 70 for safety reasons? Is this likely to set off the camera?

Secondly, say i passed a gantry that was dispaying 50mph max and what are the chances of the same gantry dropping quickly to 40mph few seconds after I went past it because at this point there is no way to know as I am already past it cruising at 50 as per it's instruction

Thirdly, what should i do if i go past a gantry with speed limit sign of say 40mph but then there are no gantries ahead or they are not showing speed limit signs on the board? does this mean i keep going at 40mph or go back to National Speed Limit?

Now I know the existence of Grace Periods and all but it appears there is no definite or consisntency across motorways or police forces when it comes to how to go about grace periods.


Many thanks in advance for all your replies.

Edited by jerrin91 on Thursday 30th August 11:47

Edited by jerrin91 on Thursday 30th August 11:53

[Pericoloso]

Smart motorway thread here ,only 1 week old.

Probably has the answers.

https://www.pistonheads.com/gassing/topic.asp?h=0&...

[jerrin91]

Pericoloso said:

Smart motorway thread here ,only 1 week old.

Probably has the answers.

https://www.pistonheads.com/gassing/topic.asp?h=0&...

read through it but not eally relevant to my question

[speedking31]

1. There is no safety reason to pass a gantry displaying 50 at 70 mph. There could be a more important safety issue ahead. Don't allow vehicles behind to push you on. If you pass a 50 at 70 then you may be penalised. You have 1 minute grace period.

2. Passing a gantry sets your personal limit. What happens later is irrelevant. Of more concern is when you pass a gantry showing 40 which is then cleared. You carry on at 40 while those behind may legitimately be travelling at 70 mph.

3. This is being debated on the other thread. Highways England information seems to contradict the law. Maybe the law needs to be updated.

[jerrin91]

speedking31 said:

1. There is no safety reason to pass a gantry displaying 50 at 70 mph. There could be a more important safety issue ahead. Don't allow vehicles behind to push you on. If you pass a 50 at 70 then you may be penalised. You have 1 minute grace period.

2. Passing a gantry sets your personal limit. What happens later is irrelevant. Of more concern is when you pass a gantry showing 40 which is then cleared. You carry on at 40 while those behind may legitimately be travelling at 70 mph.

3. This is being debated on the other thread. Highways England information seems to contradict the law. Maybe the law needs to be updated.

Hi speedking31, with regards to your first point, i wouldnt go at 70 at a 50 mph zone but lets say you are just only yards away from the gantry travelling at 70mph n then the gantry sign come up saying 50mph on the board suddenly, its not really practical to reduce the speed from 70 to 50 just like that. thats recipe for disaster.

[Pericoloso]

Read the final line of point 1 speedking posted.

[havoc]

You have either 10s or 1 minute grace - different suggestions from different sources. In any event it takes a lot less than 10s to brake from e.g. 70 to 50, even allowing for reaction time. Also 10s will see you well clear of the radar-covered area e.g. at 50mph that would be 240 yards.

Earlier this week I had a gantry go from 50 to 40 just as I was about to go under it (only just saw it at top of windscreen). I didn't see any flash from the camera.

In practice they're not THAT difficult to navigate, you just need to keep one eye* on the gantries as you approach them. And don't tailgate**.



* which IMHO makes these roads doubly less-safe than a non-smart motorway:-
1) More attention on the speed-limit signs = less on road ahead
2) Traffic all travelling at pretty close to the same speed doesn't FEEL safe - passing a HGV takes a lot longer than you'd want it to.
...oh, and 3) in some cases you lose the hard shoulder...


** Yes hypothetically one could change just as you approached it, forcing you to brake, and hypothetically there could be a car right on your tail. But as I've said that 10s is plenty of time to brake, so you'd just have to brake gradually not panic and stand on the pedal...and on these roads you're far better off letting a tailgater past you to become someone else's problem anyway...

[The Selfish Gene]

super dangerous in the wet though isn't it.

When Molly Micra sees 50mph flash up last minute and anchors up causing a safety pile up.

[zarjaz1991]

The Selfish Gene said:

super dangerous in the wet though isn't it.

When Molly Micra sees 50mph flash up last minute and anchors up causing a safety pile up.

Not dangerous, because remember, slower speed = safe. That's what we are told.

[The Selfish Gene]

zarjaz1991 said:

Not dangerous, because remember, slower speed = safe. That's what we are told.

oh yeah I forgot that bit.

In Scotland last week, very sensible signs saying effectively 'get out of the way if someone faster wants to over take'

Pissing around with speed limits on motorways from gantry to gantry is ridiculous imho.

People have enough people looking out of the clear bit at the front most of the time without overloading them with ridiculous speed restrictions everywhere.

Motorway limit is 70.

[jerrin91]

The Selfish Gene said:

zarjaz1991 said:

Not dangerous, because remember, slower speed = safe. That's what we are told.

oh yeah I forgot that bit.

In Scotland last week, very sensible signs saying effectively 'get out of the way if someone faster wants to over take'

Pissing around with speed limits on motorways from gantry to gantry is ridiculous imho.

People have enough people looking out of the clear bit at the front most of the time without overloading them with ridiculous speed restrictions everywhere.

Motorway limit is 70.

My belief exactly

[SS2.]

havoc said:

You have either 10s or 1 minute grace - different suggestions from different sources.

The legislation confirms a delay of 10 seconds from a VSL popping up to when it becomes active.

Anything longer than 10 seconds would be at the discretion / policy of the operating authority.

[speedking31]

SS2. said:

The legislation confirms a delay of 10 seconds from a VSL popping up to when it becomes active.

Anything longer than 10 seconds would be at the discretion / policy of the operating authority.

Do we think there are many incidents where delaying the enforcement of a newly displayed limit by 50 s would have a material effect on the risk of an accident?

[havoc]

speedking31 said:

SS2. said:

The legislation confirms a delay of 10 seconds from a VSL popping up to when it becomes active.

Anything longer than 10 seconds would be at the discretion / policy of the operating authority.

Do we think there are many incidents where delaying the enforcement of a newly displayed limit by 50 s would have a material effect on the risk of an accident?

It's nothing to do with accidents - smart motorways are there to enable the free-flowing of traffic and reduce the 'concertina-ing' that happens when people barrel-up on the back of a sudden queue.

...and in that regard, when operated properly they work well - M42 has certainly got more predictable since they started using them (wonder if +33% capacity may have helped too... ). Accidents / breakdowns now cause more chaos though as there's no hard-shoulder...

[TooMany2cvs]

jerrin91 said:

I am yet to drive on so called 'smart motorways'

Variable speed limits have been in place in the UK for nearly a quarter of a bloody century...

[TooMany2cvs]

The Selfish Gene said:

super dangerous in the wet though isn't it.

When Molly Micra sees 50mph flash up last minute and anchors up causing a safety pile up.

What happens when Molly Micra sees somebody do something silly, and anchors up to avoid hitting them?

[donkmeister]

These threads do always make me wonder... We've had variable speed limits on the M25 since the early-90s. As a kid I remember seeing big signs up with a very short list of instructions covering what to do when variable limits were active including "don't change lanes unless you are leaving the motorway" and "maintain a steady speed". This seemed to work and the M25 vsl does still sometimes prevent slow traffic becoming stop/start.
Now they have implemented similar systems elsewhere without the admittedly obvious instructions, and it causes confusion.
Public information campaign required? Big signs?

[The Selfish Gene]

TooMany2cvs said:

What happens when Molly Micra sees somebody do something silly, and anchors up to avoid hitting them?

Molly Micra would have done that anyway - no point in increasing risk with ridiculous average variable dangerous tax cameras

[TooMany2cvs]

The Selfish Gene said:

TooMany2cvs said:

What happens when Molly Micra sees somebody do something silly, and anchors up to avoid hitting them?

Molly Micra would have done that anyway

Then why is everybody else so bloody close that they can't react?

[The Selfish Gene]

TooMany2cvs said:

The Selfish Gene said:

TooMany2cvs said:

What happens when Molly Micra sees somebody do something silly, and anchors up to avoid hitting them?

Molly Micra would have done that anyway

Then why is everybody else so bloody close that they can't react?

probably because she is doing 40 in a 70mph road when the sign is showing 60, no, 50, no.........60.........so she will do 40 just to be sure, probably in the wrong lane, just to be sure she doesn't infringe some make believe risk limit posted for no reason other than to fleece money.

Rather than leaving the bloody thing at 70, (which incidentally is too slow and outdated).

We need to increase the standard of driving skill, not reduce it to lowest race to the bottom.

Driving should be a privilege, not a right.