Highways Agency - Safe roads, Reliable journeys, Informed travellers

Related pages

• Executive summary
• 1 introduction
• 2 existing conditions
• 3 description of proposed route
• 4 engineering assessment
• 5 environmental assessment
• 6 traffic and economic assessment
• 7 consultation
• 8 conclusions

6 traffic and economic assessment

6 TRAFFIC AND ECONOMIC ASSESSMENT

6.1 Introduction

In order to determine the feasibility of each proposed option, in terms of traffic movements and economic factors, the options were modelled using the guidelines laid out in the Design Manual for Roads and Bridges (DMRB).

The effects of traffic growth, induced traffic, accidents and construction and maintenancewere all examined as part of this process.

The costs and benefits associated with each alternative were then compared to determine the most economically viable option.

The costs consist of: investment costs, including both land costs and construction costsand also taking into account the difference in maintenance capital, i.e. the costs directlyinvolved in resurfacing etc.; operating costs, which are a reflection of the savings relatedto maintenance expenditure, a cost related to maintaining items such as drainage, fencesand signs; and indirect tax revenue, which includes taxes on fuel, oil, tyres, vehicledepreciation and vehicle maintenance.

Benefits include: travel time savings, which directly represent the time saved by road users, split into work and non-work categories; vehicle operating costs, which are often a dis-benefit associated with the wear on a car achieving a higher average speed on an improved stretch of road; delays during construction, which appear as a dis-benefit; delay savings during maintenance, which reflect the (normally fewer) delays to users during normal road maintenance; and accident savings, which provide a monetary measure of the safety of the newer road.

6.2 Traffic Modelling

The COBA11 (Revision 3) program was used to model, and to assess the economic viability of, each of the various alternative options. The COBA model required details of the 2003 Annual Average Daily Traffic (AADT) flows, as well as traffic flow factors, together with the details of the accidents along the stretch of road to be modelled. COBA also required details of traffic growth factors, which are discussed below under the heading "Traffic Forecasting".

A "Do-Minimum" node-link network was constructed to match the existing situation. Theroad geometries were input, along with the AADT flows, and this provided a base toexamine the economic viability of each option.

A "Do-Something" node-link network was then constructed for each of the individualoptions, including details of proposed road geometries. For each alternative, the schemeopening year was assumed to be 2014, and the construction period to be around 4years. The flows from the Do-Minimum network were assigned to the roads in the DoSomething network. Further details of how this was done can be found in the "Traffic andEconomic Assessment Report".

The COBA11 program then compared the Do-Something networks with the Do-Minimumnetworks to determine the economic viability of each option.

6.3 Traffic Forecasting

Traffic forecasts are required as part of the COBA assessment, as well as playing a rolein the scheme design, environmental assessment and the WebTAG appraisal. Fulldetails of the techniques and assumptions used to calculate the traffic forecasts aredocumented in the "Traffic and Economic Assessment Report".

Traffic growth estimates are provided by the Department for Transport (DfT) in the formof the National Road Traffic Forecasts (NRTF). These give forecasts for the five vehicle categories used in economic appraisal - car, light goods vehicles, other goods vehicles1, other goods vehicles 2 and public service vehicles.

In line with best practice, the growth factor for cars was modified by local informationprovided by DfT TEMPRO 4.2 programme, which contains projections of planning data ata local authority level. It was estimated that car growth in North Yorkshire would beslightly higher than the national average. Growth factors for the most likely case werecalculated, as well as optimistic and pessimistic factors, for sensitivity testing.

The estimated growth in total traffic (expected, optimistic and pessimistic) is presentedbelow).

The growth rates detailed above were then used to produce estimates of the Annual Average Daily Traffic (AADT) in the Opening Year, 2014, and the Design Year, 2029, under both optimistic (high) and pessimistic (low) growth conditions

Local transport proposals were checked to determine that they would not cause growth above and beyond the predicted growth. Estimated traffic flows with and without the scheme options show that the traffic flows in the scheme opening year are significantly different either side of Malton. To the west the AADT flows vary from 24,500 to 29,300. To the east of Malton, the ADT flows vary from 18,200 to 19,800. Advice on appropriate carriageway standards for new rural roads is given in DMRB Volume 5, TA 46/97. This quotes minimum and maximum opening year AADTs flows for Wide Single 2-lane carriageway roads of 6,000 and 21,000 respectively. It is clear therefore that a single carriageway improvement for the section of A64 west of Malton would not be appropriate. Although the flow on the section east of Malton falls within this range, current HA policy is to avoid improvements to wide single 2-lane standard over 2km in length due to perceived safety issues. Improvement to dual carriageway standard is thereforeappropriate for both sections of the A64.

The potential significance of variable traffic demand was assessed using the DfT's draftTransport Analysis Guidance (TAG) Unit 3.10.1 - Variable Demand Modelling Advice (VaDMA) - Preliminary Assessment Procedures.

Any scheme, which alters, changes travel time or costs will, in principle, affect the demand for travel. Schemes that improve travel conditions are likely to encourage some travellers to make some trips they did not previously make or to travel further ("induced traffic"). Where a scheme is not built and there is congestion, the worsening conditions as traffic grows are likely to restrict growth to less than would otherwise be the case ("trip suppression").

The preliminary assessment carried out indicated that there were currently trip suppression effects occurring in the Do-Minimum situation, and there would be would be induced traffic effects during peak periods in the Do-Something network. These effects have not been included in the traffic economics at present, as their impact on the scheme economics is predicted to be relatively minor, with a decrease in benefits in the design year of 17% (peak periods only). When considered over the whole day this is likely to represent a reduction in benefits of approximately 6%. Given the extensive nature of the scheme it is recommended that a more detailed assessment of induced traffic effects be carried out at the next stage in the scheme assessment process.

6.4 Economic Assessment

The full procedures followed for assessing the economic validity of each of the various options are outlined comprehensively in the "Traffic and Economic Assessment Report". In summary, however, the economic appraisal is based on the output from the COBA model. Allowance was made for the costs of delays during maintenance and construction; see Appendix B of the "Traffic and Economic Assessment Report" for full details. The results of the economic analysis are presented as Economic Performance Tables E1 to E3 (Appendix E), in which all costs and benefits are discounted to 1998, at a discount rate of 3.5% for the first thirty years, and 3% thereafter.

A summary of all four options is laid out below in Table 6.4. Accident benefits areincluded and monetary figures are in £M's.

• Option 1A - On-line dual carriageway improvement
• Option 1B - Off-line dual carriageway improvement
• Option 2 - Partial dualling/single carriageway improvement

From the above table it can be seen that all of the options assessed are economically justified, having positive Net Present Values. The majority of the benefits for all of the options are due to large travel time and accident savings. These more than outweigh the scheme costs combined with the increased vehicle operating costs and delays during construction.

Options 1A and 1B both have much greater Net Present Values than Option 2, due to their much higher benefits. Option 2 has the greater Benefit to Cost Ratio, as it has much lower costs than Options 1A and 1B. The economic performance of Options 1A and 1B is almost identical. Option 1A has slightly greater benefits (except for pessimistic growth) and Net Present Value but these are insignificant. The scheme costs and benefits are likely to change at subsequent appraisal stages and it is not possible to determine a preferred option in economic terms at this stage.

6.5 Accident Assessment

As part of the economic appraisal of the scheme options, COBA predicts the number of accidents on the network, together with casualty estimates. A summary of the accident savings for each option is presented in the following table.

The above figures are accident numbers and casualties saved over a 60-year period.

All of the options assessed will result in large accident savings over the sixty-year assessment period. Options 1A and 1B will result in greater accident and casualty savings than option 2. This is a result of dual carriageway roads having significantly fewer accidents than single carriageway roads. Of the two dual carriageway options, the on-line improvement will result in greater savings than the off-line improvement. This is because the off-line improvement will result in a significant volume of traffic using the existing carriageway between Malton and Seamer, which has a higher accident rate than the proposed dual carriageway.

6.6 Wider Economic Impacts

As part of the Transport Assessment Guidance (TAG) process, the wider economic impacts of a scheme must be assessed. This usually takes the form of an Economic Impact Report and an entry in the Appraisal Summary Table (AST). When a scheme will impact on an area capable of being defined in some way as a Regeneration Area (RA), this work is can often be lengthy and in-depth, requiring numerous interviews with employers and employees in the RA, and survey undertaken into the economics of the area.

Steer Davies Gleave has already undertaken such a study in 2003, and produced two reports marking their findings: "A64 Broad Based Study - Economic Impact Report", and "A64 Broad Based Study - Final Report", both published August 2003. This work was fairly comprehensive, and came to a number of important conclusions regarding the dualling of the A64. It has been decided to retain the findings of Steer Davies Gleave rather than repeat the same study. A summary of the reports' findings has been included in the "Traffic and Economic Assessment Report". The findings of Steer Davies Gleave have also been summarised for the latest AST.

The report concluded that dual carriageway improvements to the A64 would enhance the prospects for inward investment. This, combined with increased employment related to tourism, could result in the creation of an additional 800 jobs. Reduced transport costs would also benefit existing businesses and it was estimated that this could safeguard between 200 and 500 jobs that might otherwise be lost.

The Countryside Agency commissioned TRL Limited to provide a technical note on the SDG Broad Based Study, which questioned some of the findings of the study. The TRL report does not contradict the Broad Based Studies estimates for employment but stated that it was difficult to test the specifics of the estimation methodology. The Broad Based Study does make it clear that methodology used is pioneering and that the job creation figures are estimates and have been quoted indicating margins of error. The TRL report questions the economics and expresses environmental concerns of the Broad Based Study both these issues are considered to have been accounted for in the preparation of this Study Report.

6.7 Summary

The traffic and economic appraisal of the improvement of the A64 between York and Seamer has demonstrated that all three options considered are economically justified. Improving the entire section to dual carriageway standard, as opposed to leaving some sections east Malton single carriageway, would provide the greatest benefits. The level of traffic flow predicted in the scheme-opening year also indicates that dual carriageway improvement is appropriate.

As well as bringing economic benefits to road users, upgrading the A64, according to theSDG report, has the potential to bring wider economic benefits. It is estimated that a dual carriageway improvement could result in the potential creation of 800 new jobs and the safeguarding of between 200 and 500 existing jobs.

Given the above, it is concluded that there is a strong economic justification for the proposal to upgrade the A64 to dual carriageway standard between York and Seamer. Additional assessment work will be required to identify the most economically advantageous route.