Briefing – Public Safety Improvements at Junction of Liberton Brae, Kirk Brae, Liberton Road, Mayfield Road and Blackford Glen Road

Below is a really useful update from Council Officers on public safety improvements at the junction of Liberton Brae, Kirk Brae, Liberton Road, Mayfield Road and Blackford Glen Road.

Background and Context
This junction is located on the busy A701 corridor and during the am and pm peak periods (particularly am) it is extremely busy with vehicular traffic, to the extent the junction is operating over-capacity, resulting in peak period vehicular delays. Due to the location of the junction and the make-up of the surrounding area, the pedestrian activity is minimal (see below for results of recent pedestrian surveys).

Below are some background facts on the existing junction: –

  • The junction was fully refurbished circa 2000. As part of this refurbishment, “walk with traffic” pedestrian phases were provided across Liberton Brae and Liberton Road. Prior to this refurbishment, no pedestrian facilities were available. The pedestrian phase across Liberton Brae shows a green man when Kirk Brae traffic is showing a green to vehicles as there is a banned left turn in place on Kirk Brae allowing this to happen. Similarly, the Liberton Road pedestrian phase appears when Mayfield Rd traffic is running as there is a banned left turn for Mayfield Rd traffic
  • During this refurbishment, a ramp was constructed at the top of Mayfield Road (as the footway doesn’t continue around the corner) allowing pedestrians access to the Liberton Road crossing.
  • As this junction is around 20 years old, it is unlikely to be refurbished for another 10 years or so. There are many traffic signal junctions throughout the City, with significantly older infrastructure and some have no pedestrian facilities whatsoever.
  • During the above-mentioned refurbishment, investigations were carried-out to determine if staggered crossings could be installed at the top of Mayfield Rd and bottom of Kirk Brae. However, due to the need to relocate existing services (fibre optic) at the foot of Kirk Brae the costs proved prohibitive at that time.
  • Due to this junction being on a strategic route and after extensive modelling, there is no scope to install an “all stop” pedestrian stage. Nonetheless, installing islands on Mayfield Rd and Kirk Brae, to allow a staggered crossing movement, would be feasible. Blackford Glen Road would have to remain un-signalled (no pedestrian phase) as there is no way to incorporate a pedestrian phase at this crossing point without stopping all traffic. The large footway area at the bottom of Kirk Brae could be reduced in size to gain the extra width required to install a staggered island and Mayfield Rd may be wide enough already as there is currently only one large lane marked, although vehicles sometimes queue in two lanes. The gradients at the top of Mayfield Rd could prove difficult to deal with and would require further investigation to determine what engineering measures would be required.
  • Cycle early starts were introduced around 18 – 24 months ago. Their installation necessitated an overall reduction in vehicle green time of around 12 seconds. This generated larger queues in the AM peak and led to several complaints. This is an example of how over-saturated this junction is (in terms of peak traffic flows) and testament as to why an all-stop pedestrian stage (necessitating roughly 25 seconds of loss time to vehicles) would not work.
  • Estimated cost to refurbish this junction, with staggered pedestrian crossings across Kirk Brae and Mayfield Rd, is c. £450k.

Existing Junction – Facilities for Pedestrians and Cyclists
The junction has five approaches:

Google Streetview images of the junction are below.

There are Advanced Stop Lines for cyclists in place at all junction approaches.  However, the junction is not ideal for cyclists, due to its large overall size, unusual layout and some fairly steep uphill slopes i.e. when heading southeast on the Mayfield Road entry and Kirk Brae exit and south on the Liberton Brae exit.  These slopes mean cyclists are travelling more slowly, increasing the risk of conflict with vehicles.

The Active Travel team has previously investigated the possibility of improving the junction layout to assist cyclists but concluded that this would only be possible if the junction were to be fundamentally reconfigured, at significant cost.  Given other competing calls for investment in Active Travel improvements, it was considered that this could not currently be prioritised.  Early release signals phases for cyclists were, however, introduced at the junction around 18 months ago.

Existing Junction – Traffic Signals Operation
The traffic signals operate the following stage sequence: –

  • Stage 1                  Liberton Brae and Liberton Rd (green for vehicles)
  • Stage 2                  Mayfield Rd (green for vehicles) Green man across Liberton Road
  • Stage 3                  Kirk Brae (green for vehicles) Green man across Liberton Brae
  • Stage 4                  Blackford Glen Rd (green for vehicles)

Stages one, two and three are preceded by a three seconds cycle early start signal, there is no cycle early start for Blackford Glen Rd.

There are currently no controlled pedestrian crossings across Mayfield Road, Kirkbrae or Blackford Glen Road.

The traffic signals mode of operation is fixed time during the weekday AM peak between 07:00 and 09:30, running a cycle time of 120 seconds.

At all other times apart from the weekday AM peak, the junction runs vehicle actuated (VA) mode, responding to the traffic demands as required.

Road Safety – Collisions
The Road Safety team has undertaken a Collision Retrieval covering a distance of 75m in each direction from the notional centre point of the junction. This captured the whole of the junction itself and the approach to each of the junction STOP lines.

The Council uses a three-year period for investigating collision data as part of its established Accident Investigation and Prevention (AIP) protocol.  If there are three or more similar collisions within that period, the location will be given consideration for an appropriate intervention.  However, for the purpose of this investigation, a five-year search period has been used.

It is important to recognise that the Council only holds details of personal injury collisions supplied by Police Scotland, which is responsible for the collection of all personal injury road traffic collision data within its force area.  No data is available on collisions that do not involve personal injury (often described as ‘damage only’) or incidents described as “near misses”; as these types of incident do not have to be reported to the Police (or to anyone else) there is no way of collecting comprehensive data.  In addition, what constitutes a near miss is open to interpretation and any data would therefore be subjective.

Using the latest vetted data set, which is currently to the end of December 2019, there were three personal injury collisions recorded in the five-year period investigated.  The locations of these collisions are shown in Image 7, with each collision represented by a green mark.

Summary details of these collisions are as follows:

  • The three collisions resulted in four slight casualties.
  • None of the collisions involved Vulnerable Road Users (pedestrians, cyclists and motorcyclists) or anyone crossing the road.
  • Each collision occurred at a different part of the junction.
  • Collision 1 – a car collided with an unattended parked car in Mayfield Road.
  • Collision 2- a car stopped unexpectedly while travelling east – west through the junction, when the driver mistakenly reacted to a red light which did not apply to their direction of travel, resulting in following vehicles collided with each other and then it.
  • Collision 3 – a driver approaching a red light in Kirk Brae failed to react and stop in time and collided with the rear of a vehicle already waiting in the queue, pushing it into the rear of another vehicle, which was then pushed into the rear of a fourth vehicle.

There is no pattern to these collisions that would initiate a road safety intervention as part of the Council’s AIP process.

Road Safety – Speeds
The speed limit on Liberton Brae, Mayfield Road, Liberton Road and Kirk Brae is 30mph.  There are no current plans for permanent reductions in the speed limit on any of these roads.  Blackford Glen Road has a long established 20mph speed limit in place.

The Road Safety team undertakes bi-annual batches of traffic surveys at locations where speeding concerns have been raised.  Traffic data allows us to direct our resources to the locations where there is significant speed limit non-compliance. Recent traffic surveys have been undertaken at the following locations:

  • Liberton Brae, between Alnwickhill Road and Orchardhead Road, from 26 March to 1 April 2019.  A free flow average speed of 28.5mph was recorded.
  • Kirk Brae, between Orchardhead Road and Claverhouse Drive, from 29 March to 4 April 2019.  A free flow average speed of 29.7mph was recorded.

Both of these traffic survey results are within normal tolerance for a posted 30mph speed limit.

Road Safety – Pedestrian Crossing Improvements Programme
The Road Safety team manages the Council’s ongoing programme of pedestrian crossing improvements.  This delivers stand-alone crossing improvements, such as signalised puffin crossings and unsignalized zebra crossings, refuge islands and pavement build-outs.  A formal assessment and prioritisation system is used to evaluate locations and the crossing type most suitable for each location.  This system was approved by the Council’s Transport, Infrastructure and Environment Committee on 28 July 2009.  The programme does not deliver new signalised junctions or upgrades to existing junctions.

The base data which is used to assess if a location is suitable for a crossing is known as the PV2 value.  This is a nationally recognised value that indicates the number of passing vehicles and crossing pedestrians.  Pedestrian and vehicle counts are taken over the peak hours of a week day, from 7am to 10am and 3pm to 6pm, and avoiding school holidays or any other factors which might cause an abnormal result.

This base PV2 value is then adjusted to take account of local factors such as the age of those crossing, the composition and speed of passing traffic, the road width, the number of pedestrian accidents and the presence of nearby trip attractors such as schools, doctors’ surgeries, shops etc.

A location with an adjusted PV2 value of 1 or higher (2 or higher on a dual carriageway) would be considered for a puffin crossing, locations with a value of 0.3 or higher would be considered for a suite of measures that includes a zebra crossing, refuge island or pavement build-outs.  If a very low PV2 value is achieved, no additional crossing facilities may be recommended. 

Within the last three years, pedestrian crossing assessments have been undertaken at the following locations:

  • Mayfield Road, approximately 100m north of the Liberton Brae junction, on 20 March 2018.  An adjusted PV2 value of 0.216 was measured.
  • Liberton Brae, at the junction with Orchardhead Road and Tower Mains, on 20 March 2018. An adjusted PV2 value of 0.448 was measured.
  • Kirk Brae, at Double Hedges Road, on 29 May 2019.  An adjusted PV2 value of 0.026 was measured.

The locations surveyed on Mayfield Road and Kirk Brae did not therefore meet the required criteria for a pedestrian crossing facility.  It is, however, proposed to provide a non-signalised crossing improvement, such as a zebra crossing, refuge island or pavement build-outs on Liberton Brae, at Orchardhead Road and Tower Mains.  Further investigations will be undertaken to determine which would be the most appropriate option at this location.  It is currently anticipated that this pedestrian crossing improvement will be delivered within the 2022/23 financial year.

There is currently budget and staff resource capacity to progress between 10 and 15 crossing improvements concurrently, at an annual cost of around £200-250k.  The total budget available for the various road safety initiatives delivered throughout the city, including the crossing improvements programme, varies from year to year but is generally around £600-700k.

An update to the programme will be reported to the Policy and Sustainability Committee on 6 August and the updated programme will contain proposed improvements at 75 locations, representing a full work programme through to financial year 2024/25.

Provision of New Pedestrian Crossing Facilities
Established Council policy is to install signalised pedestrian crossing facilities at new signalised junctions, on all legs where there is a demand for pedestrians to cross.  In the past there has been a programme of work, with an identified budget, to retrofit pedestrian facilities at existing signalised junctions where they were missing.  However, this programme and budget were discontinued some years ago and this type of improvement is now only generally undertaken when junctions are being upgraded, either as part of a wider project or as part of the Traffic Signals team’s ongoing programme of traffic signals refurbishment work.

Spaces for People Programme
As part of the Spaces for People (SfP) programme, it is proposed to introduce temporary enhanced bus lane and cycle segregation provision along the A701 Liberton Road/Craigmillar Park/Mayfield Gardens corridor, commencing just north of this junction.

The junction is one of the top 20 locations identified by feedback submitted via Commonplace as a barrier to walking.  The SfP team still in the process of analysing the issues raised at each of these locations and considering whether there is a feasible and affordable intervention can be undertaken.  It is hoped to have this shortlisting work completed and to produce a list of publicly generated schemes within two weeks  There is, however, no current plan to take a temporary pedestrian enhancement forward at this junction as part of the SfP programme.

Google Streetview Images

Image 1 – Junction Layout
Image 2 – Liberton Brae
Image 3 – Blackford Glen Road
Image 4 – Mayfield Road
Image 5 – Liberton Road
Image 6 – Kirk Brae
Image 7 – Collision Locations


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