INVITATION TO COMMENT ON TRAFFIC PROBLEMS DISCUSSION DOCUMENT.
The Merchiston Community Council (MCC) invites comments on this Local Traffic Problems Discussion Document from local residents. Please give your name, address and contact information.
Comments should be sent to MCC Secretary not later than Sunday 5th April 2020, at email: firstname.lastname@example.org
Below is a copy of the document text for convenience
LOCAL TRAFFIC PROBLEMS DISCUSSION DOCUMENT
SUBMISSION FROM MERCHISTON COMMUNITY COUNCIL TO CITY OF EDINBURGH COUNCIL, March 2020.
The City of Edinburgh Council (CEC) has asked Merchiston Community Council (MCC) for its views, and the views of the local community, on options for change to traffic management in Viewforth north of Gilmore Place and including Viewforth Bridge.
This issue has been the subject of extended debate and concern in the Merchiston Community Council area, not least because the introduction of single traffic passage over Viewforth Bridge has had a marked negative effect on traffic flows elsewhere in Merchiston, in particular in the Yeaman Place/Polwarth Crescent/Merchiston Avenue corridor and, to a lesser, but nevertheless significant, extent in Merchiston Park.
Previous Consideration and Discussion with CEC
At its meeting in November 2018 MCC reached the formal position that:
“MCC cannot support the closure of Viewforth Bridge, and MCC has had numerous representations from residents of Merchiston Avenue concerned about displaced traffic.”
On 21 January 2019, the CEC’s South East Locality Committee heard a deputation on our traffic problems. We had previously circulated a submission (copy attached) to the Committee setting out our proposals for traffic calming measures, as a basis for further discussion. The deputation consisted of Tom Graveson, then Chair of MCC, Michael Lugton and Andrew Watt, both local residents. Mr. Graveson reiterated MCC’s opposition to full or partial closure of Viewforth bridge, and support for traffic calming measures as soon as practicable in Merchiston Avenue, whatever changes might later be made in Viewforth.
Development of current options for change
After our presentation, the SELC considered a paper (entitled ‘Viewforth Bridge Update’) from officials. The SELC concluded that officers of the Council should commission a traffic modelling exercise, provided the cost did not exceed £40,000, to assess the impact of five options: the current arrangements in Viewforth; one-way operation northbound; one-way operation southbound; partial closure e.g. during the start and end of the school day; or full closure.
Any change to the present arrangements would clearly have significant implications for the surrounding streets, as the bridge currently carries more than 3,000 vehicles per day. MCC had asked in the presentation to be involved in the development of the modelling exercise and, in her summing up, Councillor Main acknowledged the strength of local feeling and the need for it to be taken into account in developing the modelling proposal. Councillor Main also said that there was an anomaly in that traffic calming measures had been installed in Yeaman Place and Polwarth Crescent, but not in Merchiston Avenue, when the three streets form a corridor for through-traffic.
Format and Results of the traffic modelling exercise
Earlier this year CEC offered a briefing to MCC and the local community by Stephen Cuthill (a CEC official) on the results of the modelling exercise. At its meeting on 18 February, MCC concluded that the issue was of such significance that an ad hoc public meeting should be convened, and that this should be widely advertised so that anyone interested in the area could have the opportunity to attend. The date of 21 April was proposed, but that meeting is now not being arranged because of the current coronavirus situation. Mr Cuthill did however helpfully meet Michael Lugton, Community Councillor, and Andrew Watt on 16 March to make the presentation which would have been the main subject of the meeting on 21 April (that public meeting has been cancelled because of coronavirus).
As MCC understands the position from the presentation, the modelling exercise focuses on three options for the northern section of Viewforth, namely one-way operation northbound; one-way operation southbound; and full closure. (It does not, apparently, deal with partial closure.)
The exercise acknowledges some of its limitations, in particular that:
- there is no universally accepted standard or definitive guidance on calibration criteria for VISSIM modelling;
- VISSIM cannot estimate vehicle demand matrices based on traffic flow data;
- VISSIM assumes vehicles are not speeding.
MCC further understands that the model suggests that, compared with the current position, the effect on traffic levels in Merchiston Avenue (and presumably also in Yeaman Place and Polwarth Crescent) during peak periods for each of the three options would be as follows:
- Close bridge southbound
Vehicle numbers fall by 16% northbound and increase by 22 % southbound in the morning peak period; and fall by 6% northbound and increase by 12% southbound in the afternoon peak period.
- Close bridge northbound
Vehicle numbers fall by 27% northbound and fall by 13% southbound in the morning peak period; and fall by 3% northbound and increase by 3% southbound in the afternoon peak period.
- Close bridge in both directions
Vehicle numbers fall by 33% northbound and fall by 7 % southbound in the morning peak period; and fall by 11 % northbound and fall by 15 % southbound in the afternoon peak period.
At the same time, the report of the modelling exercise recognizes as one of the “Strategic Impacts” that:
“There would be an increase in traffic at Yeaman Place in the same direction as the closure, as the traffic that previously crossed Viewforth Bridge now cross at Yeaman Place”.
It also identifies as another strategic issue that:
“Merchiston Avenue traffic flow appears to remain fairly constant no matter which closure option is in place”.
This is not consistent with the claimed 27% and 33% falls in traffic numbers northbound in the morning in the event of northbound closure or full closure respectively. Nor is it consistent with the claimed increase of traffic of 22% in Merchiston Avenue in the event of southbound closure.
Finally, the report suggests that there is a need to look at the junction at Yeaman Place/Dundee Street as any closure will increase traffic flows and necessitate signalization of this junction.
Assessment of the modelling exercise
It is unfortunate that MCC and local residents were not involved in the development of the brief for the modelling exercise, as requested at the SELC meeting on 21 January 2019. We consider that, had we been so involved, we would have been able to suggest adjustments which would have yielded more credible results. In particular, the model should transparently demonstrate that the total arrivals and departures crossing the model boundary remain consistent. At present, the results appear to suggest that traffic disappears.
As the modelling exercise now stands, we do not understand, and have received no credible explanation, for the conclusion that the closure of the north end of Viewforth, either to traffic one-way or to traffic in both directions, would decrease traffic elsewhere, in particular in Merchiston Avenue. (We would point out that the bridge was fully closed for long periods during the construction of the new Boroughmuir High School, and that the universally observed effect was a significant increase in traffic in the Yeaman Place/Polwarth Crescent/Merchiston Avenue corridor; and we do not believe such empirical evidence can be ignored.)
We can see some logic in the proposition that one way operation of Viewforth might reduce traffic levels in the Merchiston Avenue/Polwarth Crescent/Yeaman Place corridor travelling in the same direction, but fail to see how it can result in falls in traffic levels travelling in the opposite direction. The report does not however appear to be internally consistent on this issue, as it recommends consideration of the installation of traffic signals at the north end of Yeaman Place on the basis of expected increases in traffic levels there regardless of which option for change is in place.
Against this background, the modelling exercise and associated report are not, in MCC’s view, a sound basis for further changes to traffic management in Viewforth at this time. We note that the consultants make the point that there remains the option of leaving the bridge open (perhaps waiting on completion of other developments in the area). In MCC’s view, this is the least bad option at present, which we understand might be coupled with minor adjustments to the present arrangements, e.g. coordination of three sets of signals between Dundee Street and Gilmore Place.
If CEC is minded to proceed with any of the three options on which the modelling exercise focusses, against the advice and views of MCC and in the light of our continuing concerns, we consider that any changes should be initially only for a temporary period, before and during which there should be monitoring of traffic flows in the MCC area to measure the effect on surrounding streets. Thereafter, there should be consultation with MCC and the local community to gauge reactions to the effects of any changes.
At the same time, we would remind CEC of the continuing public concern about the excessive volumes of traffic now using surrounding streets, which problem has been significantly exacerbated by the signal control at Viewforth Bridge. In particular we would ask CEC to give urgent consideration to the need to remove the anomaly of traffic calming measures being in place in Yeaman Place and Polwarth Crescent but not in Merchiston Avenue.
MCC is grateful to CEC for arranging a presentation to our representatives on the outcome of the modelling exercise. However, we believe that the exercise produces results which are not credible, and that the report by the consultants is in some respects internally inconsistent. We do not consider that it provides a sound basis on which to proceed with proposals for further changes to traffic management in Viewforth, and we note that the consultants themselves conclude that an option is no change in the short term, pending the completion of further developments north and south of Fountainbridge.
If, notwithstanding our concerns, CEC is minded to proceed with changes to traffic management in Viewforth, we believe that such changes should initially be only temporary, so that their effect on the MCC area can be assessed. We consider, finally, that CEC should now address the problem of overuse of the Merchiston Avenue/Polwarth crescent/Yeaman Place traffic corridor and the need for a consistent policy on traffic calming along the whole corridor.
Annex 2 – Suggested traffic management changes diagram: