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Maidstone Joint Transportation Board

16 October2019


Maidstone Bridges Gyratory – Post Scheme Monitoring


Decision Making Authority

Kent County Council/Maidstone Borough Council

Lead Director

Simon Jones

Lead Head of Service

Tim Read

Lead Officer and Report Author

Russell Boorman/Lee Burchill

Wards and County Divisions affected

Wards: Maidstone Central/High Street/Bridge/Fant  

Which Member(s) requested this report?




This report makes the following recommendations:


That the report be noted.








Maidstone Joint Transportation Board

16 October 2019

Maidstone Bridges Gyratory – Post Scheme Monitoring




1.1       This paper provides a further update in relation to the ‘One Year After          Opening Report’ for the Maidstone Bridges Gyratory scheme submitted to the South East Local Enterprise Partnership (SELEP) which is still being          reviewed by an independent evaluator.    


2.          Pedestrians:


2.1      During the survey of traffic data, pedestrian usage was observed following           the closure of the existing subways and removal of an ‘at grade’ controlled            pedestrian crossing. 


2.2      Non-Motorised User (NMU) surveys were carried out during the scheme                design to ascertain the requirements for the new ‘at grade’ crossing                      positioned at the lower High Street.  The design calculated the number of                pedestrians predicted to utilise the new crossing. 


2.3      The central ‘pen’ area was increased accordingly to a size in excess of                     33sqm.  This is sufficient to accommodate the number of pedestrians                      utilising this crossing in peak periods and also includes spare capacity for            future growth.


2.4      Observations from the survey have identified that 99% of pedestrians use                    this facility as it is meant.  There is, unfortunately, still 1% of pedestrians               who try and cross in an unsafe manner, in contravention of the highway                   code. 


2.5      This unsafe practice has not resulted in any incidents involving motorists              and is predominately pedestrians crossing the Broadway bridge having             ascended the steps from the tow path, where there is clear signage                             identifying no crossing point.


3.       Cyclists:


3.1      During the scheme design, assessments were carried out to identify any potential for including cycling provision in, on and around the gyratory system. 


3.2      Due to safety concerns and practicalities of altering existing structures, an agreement was reached with MBC to retain the existing cycling route using the Medway Street subway which remained open as part of the scheme.


3.3      Signage has been improved at the lower High Street to identify the official cycling route.    


3.4    It was observed that the more experienced cyclists do not use the official cycling provision and remain on the carriageway.  It must be noted that if cyclists wish to continue to use the ‘on road’ option, this scheme was not designed to detract from this function but to enhance the overall cycling experience for all levels of cyclist.


3.5    To date there have been no recorded incidents involving motorists and cyclists. 


4.       Traffic Data:


4.1     As previously reported weekday traffic surveys were carried out on    Wednesday 13th March 2019.          Weekend surveys were carried out on          Saturday and Sunday 16th-17th March 2019.


4.2     Surveys were carried out by Automatic Number Plate Report (ANPR) to         provide full path information for vehicles using the gyratory.  Queue length       data was collected by lane at the same time as the ANPRs.


4.3     As the traffic signals operate using variable timings to optimise for traffic,   traffic signal timing information for each stop line was collected over the      survey period.


4.4     Analysis of the survey data was carried out to identify the weekday and      weekend peak periods. These were:


                • Weekday AM: 07:30 - 08:30

          • Weekday PM: 16:00 - 17:00

          • Saturday: 12:30 - 13:00

          • Sunday: 12:15 - 13:15


4.5     Prior to running the LinSig models, a full review of both the existing and     proposed models were carried out. This highlighted a number of areas    where the models did not reflect the previous or new layout.  This is due       to alterations made to the alignment during the detailed design process.


4.6     There has been a decrease in the number of vehicles using the gyratory      system based on the initial 2013 data.  This could be attributed to the perception that the system does not perform as expected or indeed the     growth in the area has slowed since between 2013 and 2019 and TEMPRO          growth figures used in the 2019 assessments are now nationally lower           than used in 2013.   Appendix A shows the flow matrices in Passenger Car Units (PCU’s).


4.7     It is therefore concluded that the gyratory system operates in a similar        nature to that ‘without scheme’ with minor improvements for vehicles   travelling in a northern direction towards the M20.   


4.8     The LinSig models for both the ‘no scheme’ and ‘with scheme’ scenarios      were updated to include the revised 2019 predicted ‘no scheme’ traffic    flows and each model was optimised retaining the cycle times used in each         case.





4.9    Practical Reserve Capacity

          The table below gives the Practical Reserve Capacity (PRC) results from       the LinSig models:



No Scheme


2013 (Observed)

2019 (Observed

2019 (Growthed)

2013 (Observed)

2019 (Observed

2019 (Growthed)















Practical Reserve Capacity Results


4.9.1  PRC is a measure of how well a junction operates based on the operation     of the worst performing lane in one scenario.  The higher the percentage,      the more capacity is available for additional traffic.  A negative percentage       indicates the junction is operating at or over capacity.


4.9.2  As can be seen from the above table, in 2019 the scheme operates with a   similar reserve capacity to the 2013 ‘without scheme’ model.


5.0  Conclusion:


5.1   On the whole the Maidstone Bridges Gyratory has been a success.  Since opening there have been very few negative comments.  The system continues to be monitored and minor adjustments to the traffic signal timings made where necessary to maximise its’ performance.


5.2   The purpose of the ‘One Year After Opening Report’ is to provide the full picture of the scheme delivery and not just concentrate on one element of the project. 


5.3   Benefits for the local community as well as the travelling public have been realised through the construction of this scheme. 


5.4   Full results can be seen in Appendix C and D – Gyratory (Existing) & (Proposed) Basic Results Summary, Appendix B LinSig Matrices, Appendix A Peak Hour Analysis.