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Local residents all know the frustrations and difficulties caused by the layout of the roads by the Sturry crossing. By and large we live with it, and some plan their journeys to avoid the times when the barriers are down. Canterbury City Council are aware of the pollution hazard when drivers sit with their engines idling, but their rather poorly placed signs have had little effect. As part of the CCC’s ambitions to build more homes in the area, it has was proposed to build a new link road through the housing estate north of the railway line, and for traffic to rejoin the Sturry Road near the park and ride, thanks to a new £30m flyover to be built largely at the developers’ expense. To make this work, the first proposal was to divert traffic from Thanet UP Sturry Hill to a new roundabout which would take the vehicles on to the new link road. This was turned down by KCC councillors, and the applicants then submitted a new plan for the junction. Unlike its first idea, traffic from Thanet would now be permitted to turn left over the crossing, following the A28 towards Canterbury.
It became quickly apparent that the new proposals were as flawed – if not more so – than the original plan, and would lead to longer delays and more pollution.
A local businessman commissioned a report from independent transport experts, and he has given permission for it to be reproduced here. We have omitted the reports preamble, as our readers will be very familiar with the existing arrangements.
Comments can still be made to the KCC via their planning site. The application number is KCC/CA/0136/2021
This is an extract from the independent report
Areas of concern
The proposed layout
3.1 The proposed highway improvement scheme, which is shown on Amey drawing number 4300392/00/68 rev 03 dated 19.5.21 (as reproduced at Appendix A) would replace the existing priority junction with a traffic signal controlled junction. The layout would appear to remove the northern level crossing stop line with a replacement located by the access to Sturry railway station, approximately 50 m from its current position.
3.2 Signalised staggered pedestrian crossings are proposed to be located on the A28 to either side of the A291 Sturry Hill, but three of the four staggered crossing do not feature stop lines. No pedestrian crossing provision is included at the A291 Sturry Hill arm of the junction. Tactile paving is shown to be provided at each crossing, but there is no indication of pedestrian guard railing, which might be expected to prevent pedestrians from seeking to cross the junction away from the formal crossing points.
3.3 The layout has been amended from its earlier arrangement through the addition of a left turn from the A28 Island Road and a secondary central island in advance of the southbound stop line on the A28. The bus lane and bus stop has been extended to accommodate a longer bus, but retains a stop line.
3.4 The amended junction layout has been subject to a Stage One Road Safety Audit (RSA), a copy of which is reproduced at Appendix B.
Areas of concern
Intervisibility
3.5 A key aspect of any signal controlled junction is the requirement that drivers and pedestrians should be able to see each other, at the stop lines and while waiting to cross, across the whole junction. This intervisibility requirement is set out in Chapter 6 of the Traffic Signs Manual (formerly provided as part of TD 50/04; Design Manual for Roads and Bridges). Figure 3.1 below reproduces the intervisibility envelope requirement set out in Chapter 6.
The correct application of the above visibility envelope would place the envelope outside of the highway boundary to the north, east and south of the junction. As such, the envelope could not be maintained by the highway authority. In the case of the northern portion of the envelope, it would also be obscured by the building line. Interestingly, the latter point is picked up in the RSA prepared by Amey4 but the wider issue regarding the ability to maintain the intervisibility envelope on land outside of the highway boundary is not considered. This is a fundamental flaw in the design.
Pedestrian crossings
The use of signalised crossings within the proposed junction is likely to require the use of pedestrian guard railing to ensure that pedestrians do not attempt to cross away from the formal crossing points. While it is acknowledged that there is a desire to move away from the use of guard railing, its use would be reasonable in an area where pedestrian movements could otherwise be seen as a potential hazard.
3.8 There is no indication on the proposed layout plan where such railings would be located. In that regard, there are two areas of narrow footway (i.e. less than 1.5 m) where it would be impractical to place guard railing. This would suggest that the proposed layout could be unsafe for pedestrians.
3.9 Again, while one instance of a narrow footway point is mentioned in the RSA, the wider issue regarding the use of limited sections of guard railing to help guide pedestrians across what will be a complicated junction is not addressed.
3.10 What is also notable is the lack of internal stop lines for the crossings. Given the distance between the stop lines and the crossings within the junction, the potential exists for drivers who choose to run a red light could then approach the crossings where an additional stop line would serve to capture such drivers.
Junction capacity
3.11 The supporting Supplementary Transport Appraisal prepared by Charles and Associates5 considers the performance of the proposed junction against the earlier version of the layout and cites the output of a VISSIM model that makes use of delay, average speed and travel time. What is not considered is the capacity of the junction and the fact that the location of the three stop lines will result in long intergreen periods, which will introduce longer cycle times and thus an inefficient use of the proposed signals.
3.12 The report makes no reference to the effect of the level crossing, yet the design has removed the southbound stop line and placed it some 50 m to the east. This implies that the whole junction (with the exception of the left turn from the A291) will be required to stop each time the level crossing is called; which as set out earlier, would be once every 10 minutes. As there is little stacking distance for the left turn, which could in any event be blocked by a bus at the southbound bus stop, it is probable that the whole junction would be closed each time a train pulled in at the station.
3.13 This strongly suggests that there is a need for a more detailed capacity analysis of the proposed junction that, as configured, has the potential to act as a bottleneck to the detriment of both local and through traffic.
3.14 Focusing on the anticipated flows through the junction taken from the Turning Movements – With-Dev AM Peak flow diagram provided within Amey’s Transport Assessment6 that supported the previous planning application, suggests that 1,075 vehicles, including 25 HGVs could be expected to turn right from A28 Island Road to A291 Sturry Hill, with only 7 movements (all HGVs) predicted to turn left and cross the level crossing. Whilst it is understood that the junction has now been amended to allow the left turn from Island Road, the total flow across the stop line is likely to remain the same in future modelling scenarios.
3.15 Taking a standard saturation flow of 1,800 Passenger Car Units per hour and adjusting it to account for the signal time lost by the level crossing use (taken to be a reduction of 25% or 15 minutes across a typical hour) would leave a maximum flow across the Island Road stop line of 1,350 vehicles. This ignores any allowance for the proposed pedestrian crossings, junction intergreens, or the other movements which could not run simultaneously (such as the southbound movement from the A291 Sturry Road arm), all of which would further reduce the capacity at this stop line.
3.16 Based on 1,114 PCUs per hour crossing the stop line (1,082 total movements with 32 HGVs assumed to be 2 PCUs) and a Saturation Flow of 1,350 PCUs per hour, this would require the A28 Island Road lane to have a green time of circa 82.5% of the total cycle time, with the remaining 17.5% left for opposing movements, intergreens and pedestrians.
3.17 This strongly suggests the need for a detailed capacity analysis of the junction to be undertaken using LinSig rather than relying upon the output of a VISSIM model. It is noted that the Supplementary Transport Appraisal referenced earlier, indicates lower traffic flows on the A28 arm, which based on just the reinstatement of the left turn to the A28, does not appear logical or understandable.
Junction layout
3.18 As proposed, the junction layout will prevent local residents and visitors to the Co-op store from being able to access the 25 parking spaces to the rear of the Co-op when approaching from the east as the ability to undertake a u-turn has been removed. This will force those drivers to use Sturry Hill to find a convenient place to turn before returning to the site from the west, requiring additional mileage and adding traffic to the neighbouring roads. As noted in the Introduction, any improvement scheme should seek to include appropriate measures to maintain existing accessibility, improve highway safety and support local businesses in the area.
3.19 The loss of this existing manoeuvre and the resulting impact on local trips to the site is likely to impact both the local residents who live next to the Co-op site and also the store itself in terms of possible loss of revenue and custom, as well as highway safety, due to drivers seeking to make ‘u’ turns.
3.20 As part of the Supplementary Transport Appraisal reference earlier, the report includes a swept path plot of a maximum legal articulated vehicle travelling west through the proposed junction. That plot, shown at Figure 3.1 in the report, is reproduced below at Figure 3.2.
3.21 As can be seen, the proposed layout provides little room for driver error on the passage of HGVs through the junction. This suggests that the junction layout is too tight as proposed and is likely to result in damage to kerbs and street furniture. This is particularly the case with respect to guard railing and traffic signal heads.
3.22 The bus stop has been amended from the original application to provide space for a longer bus stop (approximately 11 m), but this leaves little clearance to the stop line or the pedestrian crossing point to the rear of the stop. It also makes no allowance for the potential for two buses (currently the stop has a service frequency of circa 8 buses per hour from 6 routes) or any provision to cater for a broken down bus.
3.23 As noted earlier, the station forecourt currently operates as a one way access from east to west, with access to traffic from both the eastbound and westbound lanes of the A28 Island Road. The proposed junction layout would make the current exit point an entry only with the current entry point reconfigured as a two way access. This raises a number of concerns.
3.24 The existing right turn in to the station would be removed, thereby preventing access from the south of the station. This would result in traffic needing to drive north along the A291 and return in a southbound direction in order to enter the station forecourt from the southbound traffic lane; thus adding additional traffic and unnecessary turning movements to the A291.
3.25 The two-way use of the eastern access to the forecourt would require vehicles, both cars dropping off/collecting and station/railway servicing vehicles to turn within the forecourt area. No details are shown to indicate whether this is possible and at busy times, it is likely that traffic seeking to pick up / drop off at the station would back up onto the public highway, as a result of the restricted access arrangement.
3.26 The additional width of the central island by the now two-way eastern access will serve to reduce the width of the A28 running lane and, as a consequence, will limit the ability of vehicles to turn left when exiting the station forecourt. In addition, drivers would need to be aware of the adjacent stop line and pedestrian crossing when seeking to exit the forecourt, but there is no suggestion that the forecourt exit will be subject to signal control. This therefore has the potential to place pedestrians using the crossing facility at risk and is likely to introduce delay to road users if existing vehicles cannot complete the left turn.
3.27 Finally, the proposed relocation of the northbound bus stop from the A291 to a position immediately south of the existing level crossing is of concern. In the order of 9 separate bus routes call at this stop with an average frequency of 7 buses/hour. When the relocated bus stop is occupied, drivers approaching from the south may seek to overtake the bus, with the risk of collision with oncoming traffic assuming the junction is operating with more than one arm on green at any one time.
3.28 From the above, it is clear that there are a number of issues relating to the layout of the proposed junction that should be addressed and reconsidered through a further RSA.
Cycle provision
3.29 There are no advance stop lines for cyclists and no other provision through the junction, despite the fact that there is a section of cycle lane immediately to the south of the level crossing. As noted in the RSA, the scheme should include measures to allow cyclists to safely negotiate the junction. Given the proposed layout and the lack of carriageway width past the internal islands, it is considered that cyclists could be at risk of collisions with passing traffic.
3.30 The swept path shown at Figure 3.2 also serves to reinforce the point regarding the potential danger to cyclists as the layout has little additional carriageway space
Summary and conclusions
Summary
4.1 Transport Planning Associates has been appointed by Highland Property Group Limited to provide transport planning consultancy services in relation to the highway improvement scheme proposed for the A28 in the vicinity of its properties on the A28 Island Road, Sturry.
4.2 The planning application for the A28 Sturry Road junction includes the proposed introduction of traffic signals and signalised pedestrian crossings to replace a priority junction located close to Sturry railway station and a level crossing.
4.3 On behalf of our client, TPA provided two letters of objection to an earlier planning application in relation to similar works at the above junction. In our view, the majority of the issues raised in relation to the earlier application remain.
4.4 The proposed highway layout has been amended from its earlier arrangement through the addition of a left turn from the A28 Island Road and a secondary central island in advance of the southbound stop line on the A28. The bus lane and bus stop has been extended to accommodate a longer bus, but retains a stop line. The amended junction layout has been subject to a Stage One Road Safety Audit
4.5 A key aspect of any signal controlled junction is the requirement that drivers and pedestrians should be able to see each other, at the stop lines and while waiting to cross, across the whole junction. This is described as an intervisibility envelope. The correct application of the visibility envelope would place the envelope outside of the highway boundary to the north, east and south of the junction. As such, the envelope could not be maintained by the highway authority. This is a fundamental flaw in the design.
4.6 The use of signalised crossings within the proposed junction is likely to require the use of pedestrian guard railing to ensure that pedestrians do not attempt to cross away from the formal crossing points. There is no indication on the proposed layout plan where such railings would be located. In that regard, there are two areas of narrow footway (i.e. less than 1.5 m) where it would be impractical to place guard railing. This would suggest that the proposed layout could be unsafe for pedestrians.
4.7 The proposed pedestrian crossings do not include internal stop lines. Given the distance between the stop lines and the crossings within the junction, the potential exists for drivers who choose to run a red light could then approach the crossings where an additional stop line would serve to capture such drivers.
4.8 There is no detailed capacity analysis for the junction aside from the findings of a VISSIM model. The location of the three stop lines will result in long intergreen periods, which will introduce longer cycle times and thus an inefficient use of the proposed signals. No reference is made to the effect of the level crossing, yet the design has removed the southbound stop line and placed it some 50 m to the east. This implies that the whole junction (with the possible and limited exception of the left turn from the A291) will be required to stop each time the level crossing is called – i.e. once every 10 minutes.
4.9 The proposed junction layout will prevent local residents and visitors to the Co-op store from being able to access the 25 parking spaces to the rear of the Co-op when approaching from the east as the ability to legally undertake a u-turn has been removed. This will force those drivers to use Sturry Hill to find a convenient place to turn before returning to the site from the west, requiring additional mileage and adding traffic to the neighbouring roads. This may result in unsafe ‘U’ turn manoeuvres on local roads.
4.10 The loss of this existing manoeuvre and the resulting impact on local trips to the site is likely to impact both the local residents who live next to the Co-op site and also the store itself in terms of possible loss of revenue and custom, as well as on highway safety.
4.11 As proposed, the junction layout provides little room for driver error for large vehicles. This suggests that the junction layout is too tight as proposed and is likely to result in damage to kerbs and street furniture and represents a potential risk to pedestrians on the traffic islands / using the pedestrian facilities.
4.12 There are no advance stop lines for cyclists and no other provision for cyclists through the junction, despite the fact that there is a section of existing cycle lane immediately to the south of the level crossing. Given the proposed layout and the lack of carriageway width past the internal islands, it is considered that cyclists could be at risk of collisions with passing traffic.
Conclusions
4.13 A review of the proposed highway improvement scheme of the A28/A291 junction has highlighted a number of areas of concern. They include safety concerns with regard to pedestrians and cyclists, the impact on local residents and the Co-op store, the form and layout of the proposed junction and its capacity, and the potential for a bottleneck when considering the operation of the adjacent level crossing.
4.14 In our view, the proposed junction would have an unacceptable impact on local residents and shoppers and would result in an adverse impact on the continued use of the forecourt to Sturry railway station. It would also result in a compromised layout that may leave pedestrians and cyclists at risk.
4.15 The need to incorporate the adjacent level crossing in the design of the junction improvement is likely to result in a junction with limited capacity that could act as a bottleneck to the detriment of traffic flows in the area. This could serve to undo any benefits delivered by the wider A28 link road scheme.
4.16 For the above reasons and on behalf of our client, we strongly object to the proposed A28/A291 highway improvement scheme in its current form.
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