M90 ITS Variable Speed Limit and Gantrys

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Thu 3 Jan 2013 12:10
M90 ITS Variable Speed Limit and Gantrys - GardenSlave

Hi,

Don't know if anyone knows this neck of the woods here, but just last month as part of the Forth Road Bridge replacement crossing and a bunch of new road being constructed they've added about 12 overhead gantrys to this road (more road furniture to distract us all) with vairable speed signs that illuminate.

PDF here - www.transportscotland.gov.uk/files/documents/proje...f

Question is, I was driving the other day down this road which is usally 70mph or 50mph as you get closer to the bridge, but they had these gantry signs on 40mph. But, it was 40mph written in orange with flashing orange lights on each of the 4 corners of the sign and the accompaning information board reading 'Caution High Winds'. I slowed down to 40 as I know these gantrys all have Gatso cameras on them that adapt to the variable speeds rather than all being perma-set to the national speed limit. (True?)

When these gantrys have orange speeds on them, is this just advisory? (perhaps due to the windy weather as they for sure did not have red circles round them? Reason I ask is all the 'local' traffic and trucks were crusing past me well over 50/60mph as I crawled along at 40 afraid of the cameras?

Also, while on this subject - when you pass a gantry or variable speed sign that is not illumuniated - does this mean that normal road speeds are restored? Or is it when I pass a subsequent speed limit sign that you would know to speed back up to the posted speed limit? As I said the system was only turned on last month and it's damn confusing.

Thanks guys,

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Thu 3 Jan 2013 12:28
M90 ITS Variable Speed Limit and Gantrys - craig-pd130

On the M42 around Brum, if the overhead gantry signs are not illuminated then it's 70mph. I believe the variable speed limit enforcement is only working when the signs show the speed limit inside a red circle.

If you've been through a section where the signs have indicated a lower limit (for example 50 / 60mph), when the restriction clears, the signs will show the delimit symbol.

If you didn't see any flashes from the GATSO cameras then they probably weren't working.

Edited by craig-pd130 on 03/01/2013 at 12:29

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Thu 3 Jan 2013 12:35
M90 ITS Variable Speed Limit and Gantrys - Bromptonaut

If the 'Managed Motorway' function is in action the signs show a speed limit with the required red circle. It's purpose is to regulate the flow as this is proven to increase capacity,

The message boards can also be used as in other places to give advice (road closures, queues, incidents etc). In this case advice was being given because of high winds. Unless there are special bylaws for the bridge it's not mandatory but, in the event of an accident, ignoring it may be used as evidence of lack of due care or carelessnes.

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Thu 3 Jan 2013 12:44
M90 ITS Variable Speed Limit and Gantrys - Sofa Spud

I came across these orange speed limit signs with flashing lights too, on the M25 the other day, and slowed down to obey them. I have not seen these in operation before.

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Thu 3 Jan 2013 12:45
M90 ITS Variable Speed Limit and Gantrys - Collos25

All the new gantrys like thos on the M62 are pre wired for the introduction of toll payment .

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Thu 3 Jan 2013 13:28
M90 ITS Variable Speed Limit and Gantrys - GardenSlave

Thanks, Yes I think that's right then, as the pdf guide to the new road design shows speeds with red circles, in fact it does not mention anything about orange flashing speeds

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