Agenda item

Traffic Modelling Assessment


The representative from Peter Brett Associates began by briefly explaining the report and explaining that there had been a number of documents relating to traffic modelling available on Highways England’s (HE) website as part of the statutory consultation, but these had been of limited detail and did not include options testing on how the scheme had been configured. She continued by stating that meetings had been held between Thurrock Council and HE in November and December 2018, as well as on 11 January 2019 on how the scheme had been selected and how the Council could work on the modelling with HE. She added that at the 11 January meeting, the Council and Peter Brett Associates (PBA) had been hoping to analyse traffic data, but this had not occurred. She described how instead HE had offered the Council future access to the cordoned model, which would allow Thurrock to run traffic modelling, but would not provide detailed modelling results. She stated that it would give the Council increased freedom to run their own traffic models.

The representative from PBA then gave a brief background on traffic modelling and explained that HE used a variable demand model which forecast how users might change their driving behaviour in the future, such as problems with congestion, cost of fuel, and fuel efficiency. She elaborated that the model used the average weekday in 2016, including peak morning hours of 7am-8am, inter-peak hours of 9am-3pm, and evening peak hours of 5pm-6pm. She went on to state that the model began in 2026, as this was the first year HE were hoping to have the LTC open, and also forecasted traffic in 2031, 2041 and 2051. She also described how traffic growth was estimated in two different ways, these being by using ‘committed development data’, which used available data at the time, and ‘non-committed development data’, which included future developments in the borough, such as the local plan. She explained that to model future developments in the borough, HE used global factors, such as using Department for Transport HGV data, which was not accurate.

The PBA representative discussed the outputs from HE current traffic modelling, including if the Lower Thames Crossing (LTC) was built as is currently planned. She commented that HE believed the LTC would provide relief to the A13, M25, and Dartford Crossing through journey time improvements. She quoted HE and gave the example that at the Dartford Crossing currently 11,500-14,000 passenger car units (PCU, with one PCU equating to one car, and two PCUs equating to one HGV) were crossing per hour, and this would only increase to 14,000-16,000 PCUs per hour by 2041 if the LTC was built. She again quoted HE and stated that with their testing they believed that with the LTC, traffic would be reduced by 15% on the Dartford Crossing in 2041, and by 10% on the A13 in 2041. She emphasised the point that detail was not currently available to compare traffic in 2041 with and without the LTC, but HE had verbally updated PBA. She continued that verbally HE had stated that they had considered the Tilbury Link Road in November 2017 as they had considered many options, including an all-movement A13 junction (which had been ruled out as it meant elevating west-facing slip roads which would have a negative visual impact), but these options had attracted traffic through Grays onto the A13 and removed the relief the LTC could provide. She also stated that HE had considered banning HGVs on the A1089 from the Port of Tilbury, and sending them on a Tilbury Link Road instead, but HE allegedly stated that the Port had refused this option as they wanted free flowing slip roads onto the A13, and this was one reason the Tilbury Link Road had been removed. She added that HE verbally told PBA the Tilbury Link Road had also been removed as modelling had showed it increased traffic on local roads, and the majority of port traffic using the proposed Link Road would mainly be travelling to London and the North. She added that when Tilbury 2 had been modelled, again hardly any traffic had used the Tilbury Link Road so this option had been ruled out. She confirmed that HE had recommended for the Council to run its own separate study on the Tilbury Link Road, as the option had not been completely ruled out, with a junction being included in Tilbury for a potential future Link Road.

The PBA representative then outlined the design principles that HE had refreshed based on the LTC project. The design principles had been changed to:

1. Providing a crossing which accommodated national traffic movements;
2. Maintaining major traffic movements, such as the A2 to M25 North and A13 East;
3. Not creating inappropriate use of local roads.

She elaborated that on these principles HE had designed the proposed A13 junction with no direct access from the Grays area. She continued that allowing port traffic and the A1089 was the basis for current design. She then described the Manorway junction and Orsett Cock Roundabout as the HE model showed that not many people would use the LTC for this route, as it would be quicker to use existing routes due to the relief on the A13 the LTC would provide. She then described how the model had affected the northern part of the borough, as currently at the A13/M25 North junction, 40% of traffic during the inter-peak hours were HGVs. She continued that most of this traffic arrived from the A13, M25 and A2, with most weaving occurring on the M25 North. She explained that this was the reason for the lane expansion to 3 lanes, as HE felt it would safeguard the junction, as well as allowing for local development in South Ockendon.

The PBA Representative went on to discuss why the Rest and Service Area was being proposed in Tilbury, as this was due to the spacing of service stations along the route, with a service area already along the A2. She also described how HE felt it best to have a refuelling area before the LTC to decrease the number of breakdowns in the tunnel. She felt that in addition, HE had placed the Rest and Service Area in Tilbury as a turnaround point was needed in that location regardless, so the decision had not been related to the traffic modelling. She continued by stating HE had offered the Council potential actions they could undertake, such as:

1. Testing the Local Plan accurately through modelling, before the Road Investment Scheme 2 is announced at the end of 2019, and the 3rd study commences in Spring 2019, as any improvements the Council wanted would have to be funded now.

2. Consider the progress for the Tilbury Link Road, which the Council have started.

3. Suggest that Thurrock Council put forward things they would like to influence the scheme, as listed in Table 2 of the report, which are considered complimentary measures. 

The Chair then opened the floor to questions. The first question was from the Thames Crossing Action Group (TCAG) Representative who asked if the traffic modelling had taken into account what occurred when there was an incident at the Dartford Crossing. The PBA Representative replied that HE had not considered this, but when Thurrock Council receives access to the cordoned model, this would be a model they could run. She described that through the cordoned model the Council can see what would happen if roads are closed, although this may not be very accurate as people now change their routes through the help of satnavs or decide not to travel. The TCAG Representative then stated that when this model was run, it would prove the LTC would not work. She then drew the Committee’s attention to Page 19 of the agenda and asked what the link was between the Orsett Cock Roundabout, the A1089 Roundabout and Kent. The PBA Representative replied that she would need to check the detailed notes and would reply through a written answer.

Councillor Allen then asked if constraints on the models were based on cost, as HE seemed to be pursuing the cheapest methods, without considering Thurrock. He asked what could be done to protect the people of Thurrock and its natural beauty. The Assistant Director LTC answered that this would be done through the Health Impact Assessment (HIA) and subsequent mitigation. She added that although HE only needed to meet the legal minimum requirements of the scheme, they should offer other enhancements and benefits to the Council. She then stated that this was the work PBA were undertaking by helping to identify the minimum level of mitigation required, and which complimentary measures Thurrock could receive.

The Business Representative then questioned PBA’s concern over the Asda roundabout and asked the representative to expand. The PBA Representative elaborated that although detail had not been shown, HE had explained that when the Tilbury Link Road had been tested, huge amounts of traffic had been re-routing through Grays and the urban Thurrock area. She added HE were unsure if this was because of the Tilbury Link Road or if the Asda Roundabout was simply at capacity in the future. She stated that they would be able to understand in greater detail when the Council received the cordoned model. The Business Representative then stated that the Port of Tilbury had asked for options and models on the Tilbury Link Road but had not received this from HE, although HE had stated they would send it over after the end of consultation. He added that the Port had asked again since the end of consultation, but still not received anything. The Assistant Director LTC stated she had a meeting next week with HE and would ask for a three-way meeting between the Port, the Council and PBA to take place. She also added that HE had only returned from the Christmas break this week, which may be a reason why the Port had not received anything yet.

Councillor Pothecary then stated she felt  concerned over the cordoned model, as she felt HE were hiding something, as additional information must be being held ‘behind the cordon’. She asked how reliable results would be from the cordoned model. The PBA Representative replied that HE could not give out the full traffic model due to licensing rules and data protection, but results from the cordoned model would be reasonably accurate. She added that the Council could specify traffic scenarios in the wider model. She elaborated that the way it would run in practice would be that the Council would use the cordoned model for understanding, and could then ask HE to run more accurate testing in the wider model. The Assistant Director LTC added that the ‘design freeze’ would be coming in May 2019 as data had to be tested and analysed before Development Consent Order (DCO) submission in October, so there were time pressures on the Council. Councillor Pothecary added that she felt HE were ‘running the show’ and had removed democratic accountability, as the Council were there to represent residents but could not do this properly as they couldn’t engage with the wider model. The Assistant Director LTC commented that during the examination phase the Council can question, but the process was very developer led. She added that during the examination phase HE would not want lots of unhappy public comments, or lots of evidence presented against the LTC from local authorities, so would try to offer complimentary measures as much as they could.

The PBA Representative then clarified that access to the cordoned model was still not completely guaranteed as HE still needed internal agreement. She added that HE could run analysis that the Council ask for, so if access to the cordoned model was denied then the Council could still access data. She commented that this was the first time HE had offered access to a cordoned model so they don’t have a template agreement to use. Councillor Spillman then commented that the Port of Tilbury was an important logistics hub for the country and asked how the LTC scheme could get to this stage of development without providing and sharing traffic modelling with them, and with the Council. He asked if this was normal procedure for a scheme like this. The Assistant Director LTC replied that she felt HE had under-estimated the size and scale of the project, as this was the largest scheme they would be building since the M25. She felt that HE had agreed to release the cordoned model due to concerns raised by Thurrock and other local authorities, as all parties had asked for HE to run such a high volume of traffic modelling, and HE could not keep up with requests. The Chair then stated it was not the fault of PBA that no information was available as receiving information from HE was a constant challenge. Councillor Spillman replied that HE did not even seem to know basic data such as how many cars would be travelling across the LTC, and how much the scheme would cost. The Assistant Director LTC replied that the process was iterative and ran through a separate consenting regime which started broad and then narrowed during the process. She added that by using this linear infrastructure method, more problems were caused, and this was compounded by the fact this was a complex scheme which involved lots of land parcels.

Councillor Allen added that he wanted to get this scheme right by design, and wanted traffic along the A1089 and port traffic to be free-flowing, to reduce idling HGVs and therefore reduce pollution for the residents of Tilbury. He asked how the Council can influence HE. The Chair replied that this would be answered during the next item. Councillor Pothecary then drew the Committee’s attention to Figure 3 on Page 17 of the agenda which was regarding local roads, as the diagram did not take into account what would happen if there was an incident, as she did not want the roads turning into rat-runs. She stated that on the diagram there was a lot of ‘green’ which indicated increases in traffic on local roads. The PBA Representative answered that all data in the reports was focused on strategic roads, although some of the data could be zoomed in on the links, which could be provided, although there was currently no information on how specific junctions would operate. Councillor Pothecary replied that she would like to see the zoomed in files as there were very few roads that seemed to have a decrease in traffic, which would increase the pressure on local roads. Councillor Allen then asked how HE defined local roads, as for some people the A13 and A1089 counted as their residential roads. He then drew the Committee’s attention to an incident that had occurred a few weeks ago in Aveley where a HGV had driven through the front of a shop, and asked how HGVs would be prevented from driving on local roads with the LTC. He asked if ANPR cameras could be considered as a preventative measure. The Assistant Director LTC responded that the Council could ask HE for things such as weight measures during the DCO process and during the examination phase, and the Council could look into the legal aspect of ANPR cameras. The Chair asked if the Task Force could run a workshop regarding detailed traffic data, and the Assistant Director LTC replied that once the cordoned model had been received, this was something that could happen.

The TCAG Representative asked why the particular hours of 7am-8am; 9am-3pm; and 5pm-6pm had been chosen for the traffic modelling, and if when the Council received the cordoned model they could only use data from these time periods. The PBA Representative replied that HE considered the peak times during the morning and evening, as well as the lowest levels during the inter-peak hours. She stated that the combination of both of these times showed the cost-benefit analysis of the scheme. She also replied that only during these times could data be modelled. She added that Thurrock Council could run its own model but this would take lots of time and data, and it was standard practice to use data during these times.

The Chair then summarised and stated he felt disappointed in the work of HE, and clarified that it was not the fault of PBA. He felt that HE could do better as there was now a limited amount of time until DCO submission. He added that a workshop would also be considered in two months’ time.

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