Can they get away with it?

This review by Goyt Valley SOS! of the Business Case for the A6-M60 Bypass (extending the A555) was circulated to Stockport councillors in Autumn 2017. The Business Case’s purpose is to convince the Government to provide money (£500,000) for further development to reach a stage where an application for £477 million for full construction can be made. It failed at the first attempt in February 2018, but Stockport Council intends to dust it off for further attempts to get hold of the money.

Summary of Review

Scant information: The A6-M60 Bypass Business Case offers very little information that would allow us to see how the Bypass might perform in its opening year and none at all thereafter. Will the road function as its advocates apparently believe, or will it become overloaded and a source of congestion? The information exists because modelling has been carried out to year 15, but it has not been disclosed. Some information may become available if Volume 2 is published.

Modelling not fit for purpose: The Business Case’s “fixed matrix” modelling is incapable of forecasting “induced” traffic – journeys which have been stimulated by the building of the road. This is a fundamental failing. The modelling is also flawed because it was carried out ahead of the opening of A6-MARR, which will have major impacts on local roads. The modelling uses out-of-date survey information from 2009-11. The Business Case’s conclusions are therefore built on shaky foundations.

Questionable rating: The Business Case’s key finding is that the Bypass is “very high value for money” – a rating that could increase the chances of development funding. But the Bypass only narrowly scrapes into this category. Flawed modelling and possible unsound assumptions about the completion dates of feeder housing developments may exaggerate this rating.

Cheshire and Derbyshire gain: The Bypass’s major effect will be to improve access for drivers from/to Cheshire and Derbyshire and beyond – according to the scant information provided.

Greenbelt housing estates encouraged: Improved road access from greenbelt areas south of Stockport will facilitate housing developments there.

Roads dominate: The construction of the Bypass would increase the ascendancy of private motor vehicles over other modes of transport in Stockport. Inevitably it would take the lion’s share of any transport investment funds that Stockport might benefit from, rather than public transport.

Noisy for residents: A diagram shows noise levels pumped up by the Bypass over a wide area.

Very expensive: Further development to a stage when full funding can be applied for would cost £4.4 million. A further £1.5 million for development work would be required beyond that. The cost of building the Bypass would be £477 million plus £10 million for mitigation works.



The Strategic Outline Business Case offers virtually no information about whether the A6-M60 Bypass will function effectively and what impact it will have on traffic in Stockport and the surrounding area.

It is a “strategic” or “high level” report but this does not free it from the responsibility to substantiate its contentions. We all know that if the Business Case is endorsed we will be on the road to construction, not on a path of further research – so please let the public see the evidence that justifies the huge price tag and the destruction of so much wonderful green space.

It is not as if figures are not available to the authors. A wealth of figures must have been generated by the modelling programme as evidenced by the Economic Assessment, the flow change diagrams, and noise change forecasts, for example. While the authors might not want to over-burden the Business Case with lots of figures that may tax their readers, this hasn’t stopped them from doing so at various points in the report. We are left wondering whether the authors have excluded traffic figures because they believe their readers cannot understand numerical forecasts or alternatively because the figures are problematic.

We are given no figures for how much traffic will be on the Bypass either in year one or year 15 – the last year for which modelling was done. How are we to know whether traffic is expected to keep within the Bypass’s capacity, or like the M60 become overloaded along with the streets leading to it?

Neither are we given figures for traffic on any roads that might be relieved by the Bypass or made more busy by it either in year one or year 15, with just two imprecise exceptions (see below).

We are also denied information about underlying assumptions behind the forecasts including what Greater Manchester Spacial Framework (the draft regional development plans known as GMSF) and other housing developments have been assumed to take place and when.

All the above are essential information for understanding the performance of the scheme at this stage of its development and should be made available. Clearly (and rightly) the information should be stated as preliminary and subject to change if forecasting and design develop further.

Fragments of information

There are only two numbers given for traffic volumes within the whole Business Case Volume 1 (Table 6.8). These are stated as targets rather than forecasts – difference that is not explained. These are a 20% reduction in peak hour time taken to go from Hazel Grove to Bredbury/M60 and a 25% all-day reduction in traffic on the A6. Both of these targets are for the end of year one. The effect of a 20% reduction in terms of continued queuing on Stockport Road West and Bents Lane is not explained. Continued traffic problems on the A6 between Macclesfield Road and Dialstone Lane are suggested by a prediction of air quality deterioration there (Section 3.6.32).

A flow diagram (Figure 2.28) is provided indicating changes in traffic volumes in the opening year. In the absence of figures, this diagram is difficult to interpret. Two lists accompany it – showing 12 roads that will become less busy and six that will have more traffic. Like the map, the lists cover all-day rather than peak hours, when traffic will behave differently. The lack of information about peak hours is puzzling since it is this period that is the focus of much argument in favour of the Bypass.

It may be that many questions about traffic flows in the first 15 years of the Bypass’s life are answered in Volume 2 of the Business case, but this we do not have.

Traffic modelling flaws

Concern about the lack of traffic figures is given an added edge by what we know about the traffic modelling carried out for the Business Case.

Long-serving councillors may recall that when traffic modelling was attempted for the SEMMMS Relief Road, inconsistencies came up. Because of this, modelling using variable matrices was abandoned in favour of fixed trip matrices (Appraisal of SEMMMS New Relief Road, July 2004). The Department for Transport initially rejected the modelling because fixed trip matrices are unable to forecast traffic generated by a new road (so-called “induced traffic”). They can only show rerouted traffic.

The implicit assumption of fixed-trip modelling is that all origins, destinations, time of travel and mode of travel choices remain fixed.  It is able to respond to traffic growth trends or a new source of traffic such as a new housing estate but not other new journeys. On the other hand, variable demand modelling attempts to forecast all possible journeys.

Modelling for the current Business Case employs fixed trip matrices (Section 3.4.3). Since the Business Case’s central argument is that the Bypass will ease traffic on some important roads, the reliability of its forecasts is important. One would expect that the identified reduction in car journey times would result in both transfer from public transport and in entirely new journeys being induced. There is strong evidence that both these effects occur. As a result, the modelling will under-estimate traffic flows and congestion.

“Induced traffic” is a term used to describe journeys that would not have been taken were it not for the new road or would have been taken by a different mode of transport. A new road will initially expand available road space including freeing up space on other roads. Individuals and companies will want to take advantage of  road space, shorter travel times and new routes that have become available.

The Department for Transport accepted the findings of the SACTRA independent panel of experts in 1994 who said: “An average road improvement, for which traffic growth due to all other factors is forecast correctly, will see an additional [i.e. induced] 10% of base traffic in the short term and 20% in the long term.”

A report by independent consultants for the rural campaigners CPRE this year found that major new roads increase traffic above the general traffic increases for their areas, with traffic increases of up to 47% over 20 years.

The two above reports and others show transport consultants have struggled to model induced traffic. The use of fixed trip matrices for the Business Case precludes even the attempt.

Other flaws in modelling have been referred to in earlier briefings from Goyt Valley SOS! One is the use of out-of-date surveys from 2009-11 for journey origin information (A6-M60 Stage 1 Study, page 89).  Secondly, producing a Business Case before A6-MARR has been opened introduces uncertainty into modelling of the A6-M60 road. The scale of the possible impact of A6-MARR is indicated by some of the changes shown in a flow diagram (Figure 2.27). A6-MARR is likely to produce some effects that have not been forecast.

As a result of the use of fixed matrices and of carrying out modelling with old survey information before the opening of A6-MARR, forecasts from the Business Case model are both partial and uncertain.

Given the doubt about the reliablity of forecasts being used for the Business Case, some people may wonder whether it is even worth asking to see modelling figures used in the A6-M60 Business Case. However, we would certainly know more about the Bypass and the Business Case if we had access to those figures.

“Very high value for money”?

Reliability of modelling is also relevant to the Business Case’s important Economic Assessment of the Bypass. This concluded that the Bypass was “very high value for money”.

This assessment converts benefits from the Bypass over 60 years – most notably time saved by drivers – into notional cash amounts which are totalled and set against the cost of construction.

Rating the Bypass “very high value for money” should impress those in Whitehall who allocate road-building funds. However, the Bypass only squeaked its “very high value” assessment. It would take only a 1.7% increase in costs or reduction in benefits to move it down to the next category.

The use of fixed matrix modelling might lead to an understatement of congestion. A second factor that might distort “value for money” is development assumptions, particularly GMSF.  A development such as GMSF adds more drivers to the calculation whose notional time-saving can be monetised. A discounted cash flow technique used in such calculations encourages developments to be included from the earliest possible date. This can have a big impact on the results.

Publication of the development assumptions could put such doubts to rest.

Unexplained delay

We referred earlier to the failure of trip matrix modelling for the 2004 Outline Business Case. The seven-month delay in publication of the current Business Case and continued non-appearance of Volume 2 suggests, among other possible factors, that modelling problems have again occurred. We should be informed of such problems which could have a bearing on the solidity of the Business Case and its recommendations.

A Local Model Validation Report will have been produced and should be made available. It is unlikely to refer to any abortive attempts at modelling but will tell us how well the model performs in reproducing existing traffic flows.

Other modelling – High Lane…

The diagram of first year traffic flows (Figure 2-28) previously referred to shows among other things an increase in traffic through High Lane (pictured). It has been suggested that drawing attention to this is cherry-picking if mention is not also made of 12 roads listed as receiving a reduction in traffic. This list can be seen on page 46 of the Business Case.

The forecast increase in traffic in High Lane is of particular concern because the A6 has been very congested there for years. A large increase in traffic on the A6 is already expected due to A6-MARR and other factors. Peak hour forecasts for the effect of the Bypass on High Lane, if available, might show High Lane seizing up. This would have knock-on effects on other local roads and the viability of the Business Case.

The Bypass’s effect on traffic

If A6-M60 is built A6/High Lane’s importance will grow as one of the three main routes from Cheshire through Stockport/South Manchester (Figure 2-28). If the A6 in High Lane can take it, the Bypass’s major effect will be to improve road access for drivers going north/south from/to or though Cheshire and Derbyshire. This leads to rerouting away from A34.and some other roads. Improved access for drivers from the south is likely to lead to unsustainable, low development housing developments such as would be created by the original GMSF proposals. This could quickly result in A6-M60 becoming congested. This would create pressure to increase the capacity of A6-M60, leading to a vicious circle of road and land use development turning the Bypass increasingly into a motorway style link to Manchester Airport.

Curiously, some supporters of the Business Case have declared strong opposition to building on the Green Belt, despite the Bypass facilitating such developments both through the original GMSF proposals and kindred schemes that developers will not be shy in bringing forward to take advantage of improved transport links.

There will be initial benefits for Stockport residents who suffer excessive traffic on their streets or when travelling to work by road. We do not know how large and long-lasting some of these reductions will be since traffic growth is a key assumption of transport policy.

Public transport loses

Construction of the A6-M60 Bypass for £487 million would be a decision for continuing car and truck domination over other modes of transport. Claiming the Bypass to be a multi-modal improvement fails the test of common sense. If the building of the Bypass opens up road space on the A6 and elsewhere, those gaps will be filled primarily by more private drivers not buses.

If Stockport receives £487 million to build the Bypass, it is unlikely to receive further hundreds of millions for major public transport investment. Although such sums come out of different pots, they are all part of the national transport budget.

In the SEMMMS Refresh consultation, there were far more people arguing for better public transport (217), rail upgrades (90), Metrolink (77) and bus improvements (67) than people making comments about the A6 – M60 (76). While the comments on the public transport options were all favourable, a lot of the A6 -M60 comments were negative. There is more support for public transport improvements than new roads

The Bypass’s junctions

The current plan for the Bypass (the “2006” one, see Appendices to Stage 1 Study, page 38 onwards) is designed with junctions with traffic signals on the main carriageways of the road. The Business Case says these junctions would accommodate forecast demand – this is qualified as being “within acceptable parameters” (Section 2.8.17) ie presumably quite busy! We assume this forecast relates only to the first year of operation of the Bypass since it is stated elsewhere that the design of the junction at the M60 will be assessed only for its first-year performance (Section 2.8.20). Assessing junctions only for their first-year performance seems to be high risk.

The Business Case indicates that junction design may be reviewed at a later stage of development. This could lead to the introduction of motorway style merge-diverge  junctions into the design before construction begins (Section 2.8.17).

Both sorts of junction designs have negative consequences both for drivers and residents (and also the children and teachers of Dial Park Primary School).

Traffic signals on the carriageways will produce queuing, likely to turn into congestion at times and spread on to local streets.

If, on the contrary, motorway-style junctions are adopted, these will have much greater footprint, taking land and property and coming closer to residents

The relative disadvantages of the two sorts of junctions were discussed at the SMBC Executive on 30 October 2003. The Executive preferred traffic signals on the carriageways to slow the Bypass down, thereby deterring drivers from switching from the motorways.

However, the Executive were told traffic signals would cause congestion which would be increasingly significant by the Bypass’s 15th year. Alternatively if traditional motorway style junctions with slip roads and bridges were used, it was feared the road could be overwhelmed with traffic diverting from the motorways to such an extent that local drivers would struggle to get on the Bypass.

The Bypass’s effect on local residents 

The Bypass will be very bad for many local residents, whose quality of life will suffer. The Bypass will bring insistent noise to relatively quiet parts of Stockport and to many households, as shown by the diagram in the Business Case (Figure 3.6). This is probably year one modelling so the noise will get worse until electric cars become significant among road users.

The Business Case’s assertion that traffic reductions along the A6 north of Hazel Grove will create “tranquility” is absurd.

For those living close to the route there will also be a loss of pleasant views and of opportunity to get out into the open air with health benefits.

The Business Case argues that the Bypass will result in a substantial general reduction in emissions (Section 3.6.24). As well, reductions in air pollution within local properties substantially outnumber increases in emissions in other properties (Section 3.6.34). Nevertheless inflicting worse air quality on individuals, including children, is a serious step. It should be noted that because the Business Case’s modelling is unable to forecast traffic increases induced by the Bypass, the air quality figures will underestimate emissions.

The Business Case forgets residents of Disley who already suffer illegal air quality and will suffer more if the Bypass is built.

It is well established that the Bypass will impact negatively on many residents in Lower Bredbury, Bredbury Green, Foggbrook/Offerton/Bosden Farm, Hazel Grove and Torkington. Residents of Brinnington are usually left off the list but, in fact, would be brought closer to motorway traffic if a three-lane eastbound slip road at Junction 25 is joined to the outside of the M60, as planned (Study Stage 1 Appendices from page 38).

Residents of Bredbury are often claimed as beneficiaries of the Bypass. In the opening year there will be a reduction in traffic on the A627 and Bents Lane, though the size of the reduction  particularly in the morning peak is unknown. At the same time figures in the 2004 Outline Business Case showed Bredbury would receive approximately 50,000 extra vehicles net travelling to/from the south. (61,600 vehicles on the Bypass less 11,100 vehicles diverting on to the Bypass from the A627 and Bents Lane. 68, Appraisal of SEMMMS New Relief Road, July 2004)

The Bypass’s effect on green space

The Business Case says that with mitigation the impact of the Bypass on green spaces including the Lower Goyt and Poise Brook Valleys can be restricted to “moderate adverse” (Section 3.6.2). This may be referring to many years hence when mature trees have grown back over the wide area that will be cleared for Bypass construction. Even so, to describe the damage as moderate displays a disregard for beautiful green spaces that confirms our fears.

It has been argued that were the Council to endorse the Business Case, this would merely open a period of further investigation. It is true that environmental impacts would be examined, but these were fully investigated and boxes ticked back in 2003. Flood and emissions are the two environmental impacts where the position may have changed since 2003. The Goyt and Poise Brook Valleys have already been approved for destruction.


The accident forecasts (Section 3.5.11), like many other statements within the Business Case, are weakened by the inadequacy of the overall modelling for the Business Case and its failure to show induced traffic. The 25 averted deaths modelled are spread over 60 years, since the accident forecast is being done in order to be “monetised” and fed into the Economic Assessment. Since the forecast is spread over 60 years it will be relatively unreliable. Other improvements in safety could occur during that period.

Cost of the road

Development costs for the Bypass are £4.4 million to achieve the next Outline Business Case (ie the detailed case that would be submitted to the government to obtain funding for construction) and then a further £1.5 million to achieve Government/funder sign-off for work to start. Hence £4.4 million is needed for development work to continue (Table 4.5).

Construction of the road is costed at £477 million plus £10.1 million assumed to be needed for environmental mitigation works (Section 4.3.3). No costings are provided for proposed measures to promote public transport and roads relieved by the scheme from filling up with other traffic.

This is a very expensive scheme that requires more justification than is attempted by this flawed and inadequate Business Case. It should not be allowed to proceed.