Part-Time Traffic Lights on A90

[Halmyre]

Does anyone know how the part-time lights on the southbound A90 (just before Cramond Bridge) are controlled? I generally hit them about quarter to seven in the morning, and sometimes they're on, sometimes not. I'm pretty sure the switch-on time isn't consistent from day to day - so is there a bod sitting in a control room somewhere who decides "OK, lights on!"?

[novaecosse]

I thought it was automated, in that the inbound flow of traffic was monitored so it would trigger the lights at a pre-determined rate

:edit:old press release from Edinburgh City Council

[traffic-light-man]

How have they managed a 50 limit 'when the signals are operational', a system triggered VAS or Prism type sign (I'm assuming it would have to be Prism to be enforcable)?

[Bryn666]

They haven't - it's a permanent 50mph speed limit that came into force when the signals were first activated if my memory serves.

[traffic-light-man]

Ah I see, thanks for clearing that up.

[cb a1]

They haven't - it's a permanent 50mph speed limit that came into force when the signals were first activated if my memory serves.

I can't say for certain as my memory is hazy and it's a long time since I drove in to Edinburgh, but if asked I would have said that there is a Variable Speed Limit on this section. I'm sure I've seen a sign which isn't always lit up with the 50 (in a red circle) to make it enforceable.

I'm afraid I don't know my 'types of sign' well enough to know if it's a VAS, Prism or something else.

ICBW of course

[paully]

They haven't - it's a permanent 50mph speed limit that came into force when the signals were first activated if my memory serves.

I can't say for certain as my memory is hazy and it's a long time since I drove in to Edinburgh, but if asked I would have said that there is a Variable Speed Limit on this section. I'm sure I've seen a sign which isn't always lit up with the 50 (in a red circle) to make it enforceable.

I'm afraid I don't know my 'types of sign' well enough to know if it's a VAS, Prism or something else.

ICBW of course

I Think CB A1 is right, it's a variable speed limit which only seems to be engaged at peak times. why the same system wasn't used on the new D3 stretch of the A90 (which is a higher standard but permanent 50) I don't know.

[cb a1]

why the same system wasn't used on the new D3 stretch of the A90 (which is a higher standard but permanent 50) I don't know.

I take it you mean the section near the Bridge?

ICBW as I'm not a road engineer, but I guess in terms of 'standards' it's lower than the bus lane section. It's got newer tarmac and more lanes, but for the curves, junction separation and lane changing that goes on in this short stretch, I presume there is a departure or two.

I remember not long after the M9 spur opened watching someone trying to take the curve on the bridge over the A90 at a speed >55mph (they overtook me and that's what I was doing at the time) but they weren't 'tanking it' - guess 70mph to 75mph. They clearly weren't expecting such a tight curve. Thankfully the were in the outside lane with no-one in the inside lane as they ended up on the hard shoulder!

[paully]

why the same system wasn't used on the new D3 stretch of the A90 (which is a higher standard but permanent 50) I don't know.

I take it you mean the section near the Bridge?

ICBW as I'm not a road engineer, but I guess in terms of 'standards' it's lower than the bus lane section. It's got newer tarmac and more lanes, but for the curves, junction separation and lane changing that goes on in this short stretch, I presume there is a departure or two.

I remember not long after the M9 spur opened watching someone trying to take the curve on the bridge over the A90 at a speed >55mph (they overtook me and that's what I was doing at the time) but they weren't 'tanking it' - guess 70mph to 75mph. They clearly weren't expecting such a tight curve. Thankfully the were in the outside lane with no-one in the inside lane as they ended up on the hard shoulder!

I appreciate what you're saying about the tight sliproad, but a "sharp bend" sign with a "maximum speed 50" plate below it would surely suffice? I've never seen weaving as much of a problem as the flows using the Southern sliproads at Echline junction are fairly low. The only area that may be a problem is the blind crest on the Southbound A90 where it goes around the outside of the junction.

[cb a1]

I appreciate what you're saying about the tight sliproad, but a "sharp bend" sign with a "maximum speed 50" plate below it would surely suffice? I've never seen weaving as much of a problem as the flows using the Southern sliproads at Echline junction are fairly low. The only area that may be a problem is the blind crest on the Southbound A90 where it goes around the outside of the junction.

Fraid I don't know what the regulations are in relation to departures (assuming these are what they are). Simple warning signs may not be permitted.

As I noted on another thread, Transport Scotland (I think they would have been the authority that signed the scheme off) aren't averse to raising speed limits after improvements.

[flyingscot]

They haven't - it's a permanent 50mph speed limit that came into force when the signals were first activated if my memory serves.

I can't say for certain as my memory is hazy and it's a long time since I drove in to Edinburgh, but if asked I would have said that there is a Variable Speed Limit on this section. I'm sure I've seen a sign which isn't always lit up with the 50 (in a red circle) to make it enforceable.

I'm afraid I don't know my 'types of sign' well enough to know if it's a VAS, Prism or something else.

ICBW of course

I Think CB A1 is right, it's a variable speed limit which only seems to be engaged at peak times. why the same system wasn't used on the new D3 stretch of the A90 (which is a higher standard but permanent 50) I don't know.

It is VSL. There is a sign as the M9 Spur departs which states that.