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Traffic Survey 2016

An analysis of the proposal to install traffic lights and a tramway section to allow the Bala Lake Railway extension to cross the River Dee using the existing B4403 bridge.

Introduction

One of the biggest challenges the Trust faces in constructing the extension to Bala Town station is crossing the River Dee. The original plan envisaged the construction of a new bridge next to the existing B4403 road bridge. However, there are two issues with this plan:


  1. Cost; it was projected that the cost of building  a new bridge could be as much as £1million, a huge amount of money for a relatively short section of track!
  2. Environment: the route would have encroached on to a Special Site of Scientific Interest (SSSI).


The Trust is therefore putting forward plans for an alternative option and that is to construct a tramway section of railway on the existing B4403 bridge, which would resolve both of these problems. It should be stressed that for the time being, these plans are aspirational and there is still a lot of work to be done before they can be finalised. The diagram below shows the proposed route:

Plan showing the proposal for crossing the River Dee on the existing B4403 bridge.

In order to fulfil this ambition, it was vital to commission a traffic survey to ensure that the proposed plans would be feasible. The Trust gratefully acknowledges the astonishingly generous contibution of a single donation that allowed the survery to be conduted in June 2016 by Croft Transport Solutions.


The conclusion of the report, which took into consideration the time the crossing would need to operate and accountiung for future traffic flow, reads as follows:


There should no traffic impact or highway safety issues with the principle of locating the Bala Lake Heritage railway extension utilising the proposed route along the B4403, the B4391 and Tegid Street.


The Trust is obviously delighted at the outcome of the report and is now working with the relevant authorities to take the plans forward,


A summary of the report is reproduced below.


PROPOSED EXTENSION TO BALA HERITAGE RAILWAY

PRELIMINARY HIGHWAYS ISSUES NOTE – NOVEMBER 2016

Introduction


Croft have been instructed by Bala Lake Railway Ltd to provide information to assist the determination of a forthcoming planning application for the extension of the of Bala Heritage railway.


This highways note will specifically consider the implications of proposals to provide level crossing facilities as part of the Penybont to Heol Tegid line extension.


Indicative Scheme


It is proposed that the Penybont to Heol Tegid line extension will run in a north-south alignment from Penybont Station and cross the B4403 before then crossing the bridge over the River Dee and running alongside Tegid Street. An indicative alignment for the extension is shown in the diagram above..


As part of the proposals it is proposed that introduce formal signal control facilities at the B4391/Tegid Street and B4391/B4403 junction to enable trains to travel over this section of the extension without any conflict with pedestrians or vehicles.


Existing Traffic Flows


To ascertain the existing traffic levels on the local highway network traffic counts were commissioned at the following junctions on Tuesday 14th June 2016.


  • B4391/Tegid Street priority controlled junction.
  • B4391/B4403 priority controlled junction.


The AM and PM peak hours were identified as 0800 to 0900 hours and 1700 to 1800 hours.


Growthed Traffic Flows


It has been assumed for the purposes of this analysis that the development will be completed in the year 2021. Therefore an assessment year of 2026 has been assumed which is 5 years post the development completion year.


The future year traffic flow factors have been derived using the National Traffic Model (NTM) factors adjusted by the TEMPRO regional and local growth factors for Gwynedd (Rural Main). The resultant growth factors for the AM and PM peak hours as shown below:


  • 2016 to 2026 AM Peak – 1.1115
  • 2016 to 2026 PM Peak – 1.1119


Junction Assessment


To assess the operation of the indicative signalisation scheme the LINSIG 3 computer program has been used. For the purposes of this analysis a 60 second all red stage has been included within the staging to replicate a train using the level crossing.


The 60 second time period has been derived using the information contained within the Office of Rail Regulators ‘Level Crossings: A Guide for Managers, Designers and Operators’ which was published in December 2011. This document states that barriers take up to 10 seconds fully descend or rise which leaves a total of 40 seconds for the train to clear the level crossing.


For the purposes of this analysis it has been assumed that the level crossing phase is called every cycle which over the peak period equates to it being called a total of 28 times which is extremely robust.


Table 1 below summarises the results of the 2026 Growthed Flows based on a cycle time of 125 seconds including 60 seconds 'All Red' stage for the level crossing.

Arm2026 Growthed Flows
AM PeakPM Peak
DOSMMQDOSMMQ
Tegid Street
Right/Left
29.1157.93
B4391 (N)
Right/Ahead
43.8555.97
B4391 Bridge S/B
Right/Ahead
66.6375.47
B4403 Left/Right12.7137.42
B4391 Bridge N/B
Ahead/Left
48.8837.96
B4391 (S)/Ahead Left43.8134.22

Table 1 - Summary of LINSIG Output for B4391/B4403/Tegid Street Junction

2026 Growthed Flows Scenarios

As can be seen in Table 1 the proposed signalisation scheme is forecast to operate within its theoretical capacity even based on the particularly robust assumptions detailed above. The forecast level of queuing can be accommodated without resulting in any blocking back of either of the two signalised junctions.


Summary


This summary note has considered the traffic and transportation issues relating to proposals to extend extension of the of Bala Heritage railway between Penybont to Heol Tegid. The following conclusions have be drawn within this summary note;


  • Traffic surveys have been undertaken of the B4391/Tegid Street and B4391/B4403 junctions, an assessment year of 2026 has been assumed.
  • An indicative scheme for the signalisation of the B4391/Tegid Street and B4391/B4403 junctions has been drawn up which includes the provision of a level crossing over the B4403.
  • The forecast operation of the signalisation scheme has been undertaken assuming a 60 second All Red stage for the level crossing sequence. For robustness it has been assumed that the 'All Red' stage is called every cycle during the peak periods.
  • The LINSIG analysis has demonstrated that the proposed signalisation scheme is forecast to operate within its theoretical capacity with minimal even queuing even based on the robust assumptions detailed above.


In conclusion, there should no traffic impact or highway safety issues with the principle of locating the Bala Lake Heritage railway extension utilising the proposed route along the B4403, the B4391 and Tegid Street.