September 15, 2016
Resident, commuters, long distance travellers and businesses all use the A120. But how much? Road users often speak about congestion at key junctions, causing longer journey times, but how and where is this happening? Which leads to the big question; why is this happening?
All of these questions have been investigated by the A120 feasibility study project team. The team have created a full technical report detailing their findings and are using this information make sure that A120 route options developed are targeting evidence based issues.
Our study has shown that today between 21,400 and 25,400 vehicles use this section of road every day. Up to 43% of this traffic is local journeys, while up to 68% is long distance journeys where road users are traveling to the motorway network or other major roads.
The highest volume of traffic during peak periods are at each end of the corridor and the lowest on the dual carriageway around Coggeshall. At Galley’s Corner and Marks Farm during peak periods most traffic is moving ‘though’ the junction (remaining on the A120) in both directions. Congestion is a key issue for road users and on the A120 during the morning and afternoon peak period congestion can reduce the speed of your journey by up to 47%.
The volume of traffic is starting to overwhelm junctions and push the road past its operating capacity. By 2024, it is estimated that the corridor between Braintree and the A12 will be operating well over capacity.
The table below summarises the traffic issues and underlying causes, more information on can be found in part two of this article.
|Summary of issue||Underlying cause|
|Need to support economic growth and strategic developments such as Harwich International Port and Stansted Airport.||Economic growth is a policy directive at Local, Regional and National levels.|
|Need to accommodate travel demand associated with future housing and jobs.||Increased housing and job allocations emanating from the emerging local plans in Essex and in particular in Braintree District, with 14,000 additional houses and 10,000 additional jobs.|
|Significant congestion related delay on the corridor as a whole, with journey times taking up to twice as long in peak periods compared to off-peak periods.||Link and junction related congestion in particular at the junction at Galley’s Corner roundabout and Marks Tey roundabout and on the links between B1024 Colchester Road and the A12.|
|Significant congestion related delay on links between B1024 Colchester Road and the A12 during multiple hours of the day.||Lack of capacity relative to current traffic volumes, high car usage due to lack of attractive alternatives and long average trips distance to work due to large outflow of commuters from Braintree District.|
|Severe delay and queuing at key junctions of Galley’s Corner roundabout and Marks Tey roundabout.|
|Poor journey time reliability over the whole corridor and during six hours in the eastbound direction and three hours in the westbound direction, with particular sections considered unreliable during the entire analysis period of 0700 to 1900, in particular on the approaches to Galley’s Corner roundabout and between the B1024 Colchester Road and the A12.||Significant congestion related delay resulting from a lack of capacity relative to travel demand and poor resilience associated with the narrow carriageway and lack of information on incidents.|
|Poor resilience of the corridor.||Congestion, narrow carriageway width and lack of information on incidents.|
|Corridor link infrastructure operates over-capacity during up to 5.75 hours per day leading to congestion related delay and poor journey time reliability.||Narrow carriageway width relative to traffic volumes (lack of capacity) with a high proportion of HGVs.|
|Lack of capacity at Galley’s Corner roundabout and Marks Tey roundabout.||High peak period traffic flows.|
|Severance of several villages on the corridor including Bradwell, Broad Green and Marks Tey.||The A120 is part of the SRN and has relatively high traffic volumes and proportion of HGVs and passes directly through urban areas.|
|High levels of car usage, with 74% of journey to work trips by usual Braintree District residents by car.||Lack of attractive alternatives to car and long average trip distance to work due to large outflow of commuters from Braintree District.|
|Car use is generally more attractive (time and cost) than bus and rail travel in the corridor.||Lack of direct rail links and bus priority measures.|
|Congestion related delay can reduce local air quality and high traffic volumes through urban areas increase noise.||The A120 is part of the Strategic Road Network and has relatively high traffic volumes and proportion of HGVs and passes through villages such as Bradwell, Broad Green and Marks Tey.|
|Limited potential to provide access to new developments.||Lack of capacity of the transport system to absorb additional traffic.|
|Poor safety record of the corridor.||High collision rate on the A120 relative to UK rural single carriageway rate including pedestrian and cycle collisions.|
|Poor quality NMU infrastructure, including absence of cycling facilities, poor connectivity and standard of pedestrian infrastructure and poor connectivity of bridle-ways.||Lack of space for NMU facilities within existing A120 corridor highway boundary.|
There are many policy documents which relate to the need for improvements to the A120. These relate to traffic and transport. These include:
The Essex Transport Strategy LTP3 identifies key priorities that relate specifically to the A120.
We know that there are two groups that use the A120. These are:
The following highlights that over half of traffic on the A120 corridor between Braintree and the A12 is through traffic, which includes traffic between Braintree Town and the A12, in the order of 58% to 68% when looking at the composition at each end of the corridor. It should be noted that business traffic, and therefore Heavy Good Vehicles (HGV) were not considered in this calculation.
We have looked at how, why and where people travel in terms of mode, purpose and destination. To help inform this, we have used information from the England and Wales Census 2011.
Long distance travellers include those travelling to or from Stansted Airport, Harwich International Port, and Port of Felixstowe. People travel from London, the west and north of England. Most of the strategic travellers use the A120 east of Marks Farm.
We know that most of traffic on the A120 at Marks Tey travels to and from the north on the A12, especially in the morning and evening peak hours. Only a small proportion of traffic travels to/from the A12 south.
Cars are the most common form of transport on the A120. About 70% of local people travel to work by car in Braintree. Public transport options include bus and train which have low usability. Driving is quicker and costs less than taking public transport.
The A120 presents many traffic issues. These issues include:
The following goes a bit deeper into the current traffic issues.
Trafficmaster data supplied by the Department for Transport (DfT) has been used to gain an understanding of the speeds and delays experienced along the A120 from Braintree to Marks Tey. The data used for the analysis consists of at least 80,000 observations for each hourly period during neutral months from September 2013 to August 2014. The section of the A120 analysed extends from the A131 at Great Notley to the A12 at Marks Tey. It is about 13.0 miles in length in the westbound direction and 12.8 miles eastbound.
Average speed and journey time when considering the entire length of the corridor are shown in Table 2.
Table 2 Average journey times and speeds in peak periods
|A120 Direction of Travel||Journey Times (minutes)||Average Speed (mph)|
|0800 – 0900||1700 – 1800||Free Flow||0800 – 0900||1700 – 1800||Free Flow|
Table 2 shows that:
The variation in speed along the corridor is shown in for both the AM (0800-0900) and PM (1700-1800) peak hours in Figure 1 and 2.
Figure 1 Average journey speeds (mph) during AM peak hour
Figure 2 Average journey speeds (mph) during PM peak hour
Figure 1 and 2 highlight that:
This suggests that the overall corridor journey times are being significantly impacted upon by conditions at Galley’s Corner roundabout, Marks Tey roundabout and through the entire section between the eastern end of Coggeshall Bypass and Marks Tey roundabout.
Congestion is a result of delay caused by other road users on the network relative to the capacity of the roadway, characterised by slower speeds and longer journey times.
A congestion indicator was calculated as a percentage of peak hour speed (between 7-9am and 5-7pm) compared to free flow speeds (outside of peak hours, when not impeded by traffic).
The congestion indicator is calculated as the average journey time between 2000-2400. Table 2 shows the congestion indicator for the peak periods on the A120 between the A131 and the A12. It shows that between 5-6pm, eastbound traffic is 53% of the free flow speed. This means that the average journey time in the peak hour is almost twice as long as the free flow journey time.
Table 3 also shows that congestion affects eastbound and westbound journey times between 7-9am.
Table 3 Congestion indicator for the entire corridor in the peak period
|A120 Direction of Travel||Congestion indictor|
|AM Peak Period||PM Peak Period|
|0700 – 0800||0800 – 0900||1700 – 1800||1800 – 1900|
Journey time reliability is a measure to capture the variation in journey times that travellers are unable to predict.
Journey time reliability for this study is defined as a percentage of ‘on-time’ journeys in each separate hour between 07:00 and 19:00, based on observations for 246 days between September 2013 and August 2014. To be ‘on-time’ the journey must be within 20% of the average journey time for that hour.
The benchmark for Essex Priority Route 1 (PR1) inter-urban network is 95% of journeys ‘on-time’ during the 12-hour period, with routes below 95% classified as ‘unreliable’. Both the eastbound and westbound direction of travel on the A120 is unreliable, with less than 95% of journeys arriving within 20% of the average journey time for the hour in which they were undertaken.
The areas responsible for this unreliability are:
This is shown in Figure 3.
Figure 3 Journey time reliability along the A120 corridor
Traffic volumes on the A120 can be characterised as follows:
In addition to link flows, turning movement data at key junctions was analysed to understand the key movements. The key points as follows:
This implies that solutions to congestion at the above junctions need to address the major A120 through movement.
The key points regarding traffic flows and specific junctions are that:
When compared with using the car, analysis of train and bus routes highlights the following:
Why does the current traffic situation need to be addressed?
The transport related problems and underlying causes outlined above would all be exacerbated over time as the demand for transport on the strategic A120 corridor increases.
The vision for Essex is for a transport system that supports sustainable economic growth and helps deliver the best quality of life for the residents of Essex. Braintree Town is identified as a main town and a future growth area. Colchester is a regional centre and Stansted Airport and the ports at Harwich and Felixstowe are located nearby. The traffic issues need to be addressed to achieve the vision for Essex for a prosperous future.
The current significant level of congestion related delay and poor journey time reliability experienced on the section of the A120 between Braintree Town and the A12 at Marks Tey will increase as a result of future increases in traffic volumes resulting from increased demand for travel relative to the available supply of roadway capacity or public transport provision.
The following provides a description of the key potential future impacts of not addressing the transport related problems and their underlying causes as identified in the previous section.
There are some constraints on generating detailed scenarios relating to future traffic including:
The following provides an overview of issues that will influence future traffic.
The Essex County Council Transport Strategy (2011-2026) identifies the following policy that is directly related to the A120 corridor:
The Braintree Core Strategy (2010) outlines the following policies with regards to future land use within the context of their spatial strategy:
The current and emerging local plans for Braintree District identify more specifically the quantity and location of new housing and jobs and are outlined in the following section.
Figures 3 and 4 show traffic flows and network stress in 2024 during AM and PM peak hours. This is based on assumptions made on traffic growth for the estimated opening year (2024).
Figure 3 Traffic flows and network stress in 2024 AM peak hour
Figure 4 Traffic flow and network stress in 2024 PM peak
Figures 3 and 4 highlight the following regarding future link capacity relative to estimated traffic volumes:
 Average speed on A120 between Galleys Corner and Marks Tey Roundabout in the peak period indicated, expressed as a percentage of the average free-flow speed.