VOLUME S ASSESSMENT AND PREPARATION OF ROAD SCHEMES SECTION 1 ASSESSMENT OF ROAD SCHEMES PART 4. SH l/97

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1 DESIGN MANUAL FOR ROADS AND BRIDGES VOLUME S ASSESSMENT AND PREPARATION OF ROAD SCHEMES SECTION 1 ASSESSMENT OF ROAD SCHEMES PART 4 SH l/97 THE TRAFFIC AND ECONOMIC ASSESSMENT OF ROAD SCHEMES IN SCOTLAND SUMMARY This Technical Memorandum sets out the requirements for the traffic and economic assessment of road schemes in Scotland. It supersedes SH 2/91 and also indicates that SH 2/86 and SH 3/89 (including Amendment No. 2) are withdrawn (all DMRB 5.1). INSTRUCTIONS FOR USE 1. Remove SH 2/84, SH 3/X9 (including Amendment No.2 ) and SH 2/91 from DMRB 5.1 and archive as appropriate. 2. Tnsert SH l/97 into Volume 5, Section I, after Part Archive this sheet as appropriate. Note: A quarterly index with a full set of Volume Contents Pages is available separately from the Stationery Office Ltd. May 1997

2 Volume 5 Section 1 Part 4 SH l/97 Registration of Amendments REGISTRATION OF AMENDMENTS Amend No Page No Signature & Date of incorporation 0 amendments Amend No Page No Signature & Date of incorporation of amendments May 1997

3 Registration of Amendments Volume 5 Section 1 Part 4 SH 1197 REGISTRATION OF AMENDMENTS Amend No Page No Signature & Date of incorporation of amendments Amend No Page No Signature & Date of incorporation of amendments May 1997

4 DESIGN MANUAL FOR ROADS AND BRIDGES a VOLUME 5 ASSESSMENT AND PREPARATION OF ROAD SCHEMES SECTION 1 ASSESSMENT OF ROAD SCHEMES PART 4 SH l/97 THE TRAFFIC ASSESSMENT IN SCOTLAND AND ECONOMIC OF ROAD SCHEMES Contents Chapter 1. Introduction 2. Context 3. Assessment Methods 4. Guidelines for Assessment 5. Data Sources 6. Reporting Procedures 7. Before and After Monitoring 8. References 9. Enquiries Appendix A Traffic and Economic Evaluation Report Form May 1997 SH l/97

5 Volume 5 Section 1 Part 4 SH l/97 Traffic and Economic Assessment in Scotland Chapter 1 Introduction 1. INTRODUCTION General Structure of this Memorandum 1.1 This Technical Memorandum sets out the requirements for the traffic and economic assessment of road schemes in Scotland, with specific reference to the NESA program (Network Evaluation from Surveys and Assignments). It supersedes SH 2/9 1 Traffic and Economic Evaluation using the NESA Computer Program and also indicates that the following technical memoranda are superseded (all DMRB 5.1): l SH 2/X6 Scottish Traffic and Environmental Appraisal Manual (STEAM) l SH 3/S9 National Road Traffic Forecasts (including Amendment Number 2) 1.2 It explains the procedures to be used by Local Authorities and Consulting Engineers when undertaking traffic and economic assessments for trunk road schemes and describes the reporting and data storage requirements of The Scottish Office. It indicates that the NESA Manual (DMRB Volume 15) now contains the National Road Traffic Forecasts (previously in SH 3/89) and that the traffic advice in the STEAM Manual has been replaced by the guidance contained in DMRB Volume 12 Traffic Appraisal of Road Schemes. (The environmental guidance contained in STEAM was superseded by the publication of DMRB Volume 11 Environmental Appraisal.) 1.3 This Technical Memorandum refers to the more detailed guidance on specific issues contained within DMRB Volumes 5, 12, 13, 14 and 15 (see Chapter 7). 1.4 Chapter Two provides advice on the role of traffic and economic assessment, the stages of a trunk road scheme at which appraisals should be prepared, and the impact on procedures of the recent SACTRA report. In addition, Chapter Two defines the terms used in the Memorandum and introduces fixed and variable trip matrix assessment. 1.5 Chapter Three introduces scheme classification and provides advice on the selection of appropriate appraisal methodologies and computer programs. 1.6 Chapter Four gives more detailed guidelines on both traffic and economic assessment, with particular reference to traffic forecasting. 1.7 Chapter Five discusses the primary data sources for traffic and economic assessments. 1.S Chapter Six defines the reporting requirements for traffic and economic assessments, including the Scheme Classification Report, the Traffic Survey Report, the Local Model Validation Report, the Forecasting Report, the Economic Appraisal Report and the Traffic and Economic Evaluation Report form. 1.9 Chapter Seven outlines The Scottish Office Before and After Monitoring procedures and their objectives. May 1997 SH l/97 l-l

6 Volume 5 Section 1 Chapter 2 Part 4 SH l/97 Traffic and Economic Assessment in Scotland Context 0 2. CONTEXT The Role of Traffic and Economic Assessment in Trunk Road Appraisal 2.1 Figure 2.1 illustrates the scope of this Memorandum in the context of a complete trunk road scheme appraisal as set out in DMRB (TD 37/93). 2.5 Traffic assessment should be carried out in accordance with DMRB Volume 12 which supersedes the Scottish Traffic and Environmental Appraisal Manual (STEAM) and the related Technical Memorandum, SH 2/X6. Economic assessment should be carried out in accordance with DMRB Volume 15 The NESA Manual, with reference to DMRB Volumes 12, 13 and 14 where appropriate. I I I 2.6 Cost benefit analysis can be applied throughout scheme preparation and should be used to contribute to the following decisions: l the assessment of the need for a corridor improvement ASSESSMENT ENVIRONMENTAl ASSESSMENT l the selection of the preferred scheme out of several mutually exclusive options l the selection of optimal link design standards a igure 2.1 The Components Appraisal of a Road Scheme 2.2 The assessment of environmental effects is dealt with jn DMRB Volume 11 and the guidance on operational assessment is provided in DMRB Volume The complete apprajsal hinges on the outcome of operational, economic and environmental assessments. Important inputs to each of these assessments are the changes in traffic conditions that result from the road improvement and/or the growth of travel demand through time. 2.4 Methods are therefore set out in this Memorandum for both traffic and economic assessment. The traffic assessment provides forecasts of future traffic levels on the scheme being considered and the economic assessment provides a formal and consistent cost benefit analysis. l the selection of optimal junction types l the ranking of schemes in the Roads Programme l the optimal timing of a scheme (including the consideration of the merits of staged construction) Stages of Assessment 2.7 Formal traffic and economic assessment reports should be prepared for all trunk road schemes costing more than &lm (and for designated schemes costing under &lm) after completion of the following stages of scheme assessment (see DMRB 5.1.2): l Stage 1 - Preliminary Assessment l l Stage 2 - Route Option Assessment Stage 3 - Preferred Scheme Assessment May 1997 SH II97 2-l

7 Chapter 2 Volume 5 Section I Context Part 4 SH l/97 Traffic and Economic Assessment in Scotland 2.X Thereafter, a review of the traffic and economic assessment may be undertaken at pretender, post-tender and post-construction stages although this may depend on the timing of the scheme and the Before and After Monitoring requirements (see Chapter 7). Traffic Assessment 2.9 Following the acceptance by the Department of Transport of the recommendations made by the Standing Advisory Committee on Trunk Road Assessment (SACTRA) in Trunk Roads and the Generation of Traffic (HMSO, 1994), the requirement for traffic and economic assessments of trunk road schemes has become more onerous Schemes must now be classified to reflect their susceptibility to induced traffic, the level of which will determine the appropriate traffic and economic assessment techniques to be used. This is discussed in the following chapter This scheme classification exercise is designed to ensure that appropriate assumptions are made about how the trip matrix (i.e. the number and distribution of trips) might be influenced by the introduction of a scheme. The two options which exist are to adopt fixed or variable trip matrices With a fixed trip matrix, the number and distribution of trips remains constant with and without the scheme in place. The traffic analysis is therefore relatively straightforward since it only has to deal with the assignment of these trips (route choice) With a variable trip matrix assessment, the number and distribution of trips changes when a scheme is introduced, due to the variety of behavioural responses that can occur when changes in accessibility are made. The traffic or transport analysis therefore requires the application of complex techniques to identify the changes in the trip matrix However, for all assessments which include variable trip matrices, a fixed trip matrix comparison will be required The traffic assessment methodologies are discussed further in Chapter 3. Economic Assessment 2.16 At the heart of an economic assessment is the technique of cost benefit analysis. For the economic assessment of a road improvement, the cost benefit analysis is designed to measure the net social benefit of the scheme by comparing the sum of the benefits generated to the sum of the costs incurred over a thirty year period (see DMRB Volume 15) Cost benefit analysis is used to test the value for money of trunk road schemes although it is accepted that this is only a partial technique since it does not measure value for money over the whole range of costs and benefits, particularly those broadly classified as environmental. 2.1X In general, society prefers benefits to accrue sooner rather than later and to allow for this, economic assessment tools progressively discount each year s costs and benefits to a present value for a given base year. Provided a common price base is adopted, this allows these costs and benefits to be legitimately added and compared. For all economic assessments, the current base year for prices and values is With effect from 13 March 1997, the discount rate to be used in the appraisal of road schemes and related expenditure has been brought into line with that used elsewhere in the public sector, that is 6% (see Economic Appraisal in Central Government.- A Technical Guide for Government Departments, Stationery Office, 1997) If variable trip matrix traffic assessments are carried out, the economic assessment methodology must be able to deal with variations in the trip matrix The software packages available for fixed and variable trip matrix economic assessments are discussed in Chapter SH l/97 May 1997

8 0 Volume 5 Section 1 Chapter 3 Part 4 SH l/97 Traffic and Economic Assessment in Scotland Assessment Methods 3. ASSESSMENT METHODS Scheme Classification 3.1 Following the recommendations of SACTRA in Trunk Roads and the Generation of Traffic (HMSO, 1994) all schemes should now be assessed for the potential to induce traffic following the advice contained in Induced Traffic Appraisal (DMRB ). 3.2 Schemes should be classified into one of three categories - simple, intermediate or complex and assessed against the following criteria: a) Are the existing roads in the study area operating close to capacity, or are they expected to do so within the design life of the scheme? In these circumstances, congestion is likely to lead to suppression of traffic effects, and schemes may result in the release of some of the suppressed traffic. b) Is the potential change in overall trafic jlows high with respect to changes in travel times or COSlS? This is likely to be the case where there are good alternatives available for the movements affected by the proposed scheme, e.g. other routes or public transport alternatives. c) Will the implementation of the proposed scheme cuuse large changes in travel costs, road capucity or both? These conditions are likely to occur where the scheme or improvement bypasses extended lengths of low standard or congested network, or where new links cause major changes in accessibility (e.g. estuarial crossings) 3.3 Assessment of each of these criteria for a given scheme will rely upon a combination of quantitative and qualitative factors. Each of the three criteria must be considered separately and given a low, medium or high marking, to provide an overall assessment. Advice on the classification of schemes is contained within Induced Traffic Appraisal (DMRB ) and summarised below. 3.4 Simple schemes are those where low markings are given for all criteria. Fixed trip matrices are sufficient for these types of schemes because the pattern of travel demand is unlikely to differ significantly between the base and improved networks. 3.5 Intermediate schemes are those where one of the criteria above merits a high marking or where IWO or three of the criteria merit medium markings. Variable trip matrices are appropriate for schemes in this category and their use should be considered as sensitivity testing on a fixed trip matrix analysis. 3.6 An initial sensitivity test using the techniques set out in Induced Traffic Appraisal (DMRB ) is suggested as the best way to determine the methodology to be used to derive the variable trip matrices, e.g. elasticity techniques. 3.7 These schemes are likely to require further assessment to establish if they may be more appropriately classified as complex. 3.X Complex schemes are those where nzore than one of the criteria indicated merits a high marking. Variable trip matrices are appropriate for schemes in this category. A fixed trip matrix analysis should, however, be carried out for comparison purposes. 3.9 A detailed appraisal of specific behavioural responses is likely to be required using the techniques described in Induced Traffic Appraisal (DMRB ). Elasticity techniques are unlikely to be a satisfactory way of deriving the variable trip matrices, particularly since mode choice modelling may be required to allow specific consideration of public transport The classification of a trunk road scheme is subject to Scottish Office approval through the submission of a Scheme Classification Report (see Chapter 6). May 1997 SH l/97 3-l

9 Chapter 3 Volume 5 Section I Assessment Methods Part 4 SH l/97 Traffic and Economic Assessment in Scotland Applicability of Traffuz and Economic Assessment Software 3.11 NESA (Network Evaluation from Surveys and Assjgnments) and REVS (Route Evaluation by Vehicle Simulation) are the standard Scottish Office tools for use in the traffic and economic assessment of trunk road schemes in Scotland. COBAlO (see DMRB Volume 13), URECA (DOT, 1996) and other approved economic assessment programs can be used with the prior agreement of The Scottish Office The NESA Manual (DMRB Volume 15) supersedes the NESA User Manual (Scottish Office, updated 1992) and the REVS Manual is available from the Scottish Office Approval for the use of economic assessment programs other than those specified may be granted through discussion with The Scottish Office including presentation of an audit report which demonstrates compatibility with the standard software. Approval must be granted in advance of it being used on a Scottish trunk road scheme appraisal COBA 10 and URECA require the development of a traffic model whereas NESA and REVS include a traffic model in their suite of software (although NESA can interface with other traffic models to perform only economic assessment) NESA is primarily designed for the assessment of rural improvement schemes where route options are involved (e.g. rural bypass scheme). REVS includes an approved economic assessment module and is particularly appropriate for schemes on single carriageways where there is a clear need for improvements in overtaking provision (e.g. on-line widening schemes) The use of URECA (or other approved economic assessment program) may be more appropriate where a traffic model has been developed on software other than NESA and where the use of variable trip matrices is required as part of the assessment Economic assessments can be carried out on a link or matrix basis. The economic calculations in NESA, REVS, COBA and URECA are all link based. It is acknowledged, however, that matrixbased calculations have advantages both in the presentation of results and in ease of computation, particularly for variable trip matrix assessments Both methods are known to be equivalent for the calculation of time savings but can differ for vehicle operating costs, accidents and maintenance costs. Any proposed matrix-based method should therefore demonstrate compatibility with linkbased calculations The Scottish Office recognise the benefits of matrix-based economic assessment techniques and will therefore consider approving programs which adopt this technique User costs incurred during construction and routine maintenance (e.g. driver delays and accidents) should be calculated using the Department of Transport s QUADRO program (Queues And Delays at ROadworks), details of which are given in DMRB Software Selection (Traffic) 3.21 As previously discussed, a variety of traffic modelling packages are commercially available, including NESA and REVS. This sections provides some guidance on the applicability of different modelling suites in relation to scheme classification:. NESA - suitable for simple (usually rural) schemes, where traffic is not expected to reroute in response to future year congestion l REVS - suitable for simple (usually rural) schemes, where traffic is not expected to reroute in response to future year congestion and where overtaking opportunities have a significant influence on vehicle speeds. 3-2 SH l/97 May 1997

10 Volume 5 Section 1 Chapter 3 Part 4 SH l/97 Traffic and Economic Assessment in Scotland Assessment Methods. Congested Assignment Models - which capture re-routeing effects due to congestion, particularly those caused by congested junctions (e.g. SATURN, TRIPS, CONTRAM, etc.) are suitable for the assessment of sjmple and intermediate schemes. Some of these models may be also be used in the highway assignment component of transport models for complex schemes. Software Selection (Economic) 3.22 The complexity of the required economic assessment will be dependent upon the scheme classification discussed earlier. The following sections give advice on the use of the available economic assessment packages according to scheme classification. l Simple Schemes - use MESA, REVS or COBAI 0 l Intermediate Schemes - use URECA or other upproved economic assessment program l Complex Schemes - use URECA or other approved economic assessment program to assess the impacts on road users. Additional programs will therefore be required jbr assessing public transport impacts, etc Although the development of schemespecific packages may be required for complex schemes, The Scottish Office intend to release standard programs for use in conjunction with the development of the Central Scotland Transport Model. Further information will be provided on these programs when they are available. May 1997 SH II97 3-3

11 Volume 5 Section 1 Part 4 SH l/97 Traffic and Economic Assessment in Scotland Guidelines Chapter 4 for Assessment 4. GUIDELINES FOR ASSESSMENT 4.1 As discussed previously, DMRB Volumes 12, 13, 14 and 15 give guidance on most aspects of traffic and economic assessment. Where additional information is required or where the available guidance can be usefully summarised, it is included below. Traffic Forecasting 4.2 Traffic forecasting is a fundamental component of road scheme appraisal. Traffic forecasts are usually derived through the use of a traffic model of varying degrees of complexity. These traffic models require to be fully calibrated and validated to give confidence in forecast traffic flows. 4.3 To reflect the uncertainty in forecasting traffic flows, traffic growth is normally modelled through the use of two growth scenarios, high and low growth. These two forecasts reflect different economic growth assumptions, particularly in relation to fuel prices, car ownership levels and goods vehicle traffic growth. 4.4 The default growth factors in NESA and REVS are the National Road Traffic Forecasts (see DMRB Volume 15). These forecasts predict growth in vehicle-kilometres, not trips, and it may therefore be appropriate to make an adjustment for this, depending on the size of the traffic model. DMRl (Chapter 12) should be considered and Scottish Office advice sought. 4.5 Local growth factors should be considered for use where: l historic local traffic growth rates are different from NRTF l significant traffic generating developments are likely in the study area l local network constraints are expected to limit traffic growth 4.6 It is, however, important that local traffic forecasts are not only consistent with one another, but also share a common basis with the National Road Traffic Forecasts (NRTF). 4.7 The approach to forecasting should therefore be agreed with The Scottish Office. Local growth factors may be derived from local planning data in conjunction with the use of TEMPRO (Trip End Model PROjection) but The Scottish Office must be consulted prior to their use. The relationship between the local planning data forecasts and the TEMPRO forecasts should always be investigated through consultation with The Scottish Office. 4.8 For a full discussion on traffic growth factors, see DMRB (Chapter 12). 4.9 Results are to be submitted to The Scottish Office for both low and high traffic growth forecasts. Definition of Base and Design Networks 4.10 The first stage in an economic assessment is to define the alternative options to be appraised. The minimum number of options is two, namely a Do-Minimum (Reference Case) and a Do- Something option (Variant Case). In most situations, however, there will be several Do- Something options under consideration. While these terms appear self-explanatory, they raise some fundamental issues The Do-Minimum scheme (or option) is the base road and traffic network against which the relative merits of alternative improvements can be consistently evaluated. In many cases the definition of the Do-Minimum is straightforward; it is simply the existing network without modificatjon, that is a Do-Nothing scenario However, one or more of the following situations may arise in which the Do-Minimum differs from the Do-Nothing: l changes to the road network outwith the study l where works will be carried out in the Doarea are likely to affect the number of trips Minimum network regardless of whether or not passing through the study area the Do-Something scheme is built May 1997 SH l/97 4-l

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13 Volume 5 Section 1 Chapter 4 Part 4 SH l/97 Traffic and Economic Assessment in Scotland Guidelines for Assessment 4.25 Therefore, where an up-to-date database of Scottish construction prices is used to derive the construction cost estimate, only the Retail Price Index (RPI) should be used to convert costs to different price bases Where the Department of Transport s Road Cost Model is used to derive cost estimates, construction costs should be adjusted using the appropriate RPI value and a Relative Price Factor (RPF), details of which are provided in both the NESA and COBA Manuals (DMRB Volumes 15 and 13) Economic assessments should be updated when significant changes to the estimated construction cost are made. This does not need to involve further traffic modelling unless the scheme has changed significantly or the proposed opening date has been changed. During scheme preparation (Stages 1 to 3), economic assessments should be updated annually in this way. Assessment of Maintenance Costs 4.28 Trunk road maintenance has become a significant problem in recent years as a result of the increase in numbers of heavier lorries and the ageing of the road network. The major costs of maintenance work are borne by road users in terms of traffic delays The computer program QUADRO (QIJeues And Delays at madworks) calculates the total works and the user costs of maintenance either specified individually or as part of a life-cycle profile of maintenance activity over a 30 year period, the assumed life of the road. The traffic delay costs are assessed using both low and high forecasts of future traffic growth. These traffic growth forecasts should be consistent with those used in the traffic modelling QUADRO has been designed primarily for use on trunk roads, but it may also be of value to local authorities for non-trunk roads. The main use, however, is likely to be for the motorway network and for these parts of the all-purpose network which carry high flows, particularly of heavy vehicles. Whether or not to proceed with a scheme. In most cases the standard assumption that maintenance costs on a new or improved of road will be offset by savings on the old network will apply, but in a few cases, and notably road widening proposals, the costs of maintenance in the future without the improvement can be crucial. The choice between alternative schemes. Differences in future maintenance costs may be sufficient to swing the balance in a few cases, but generally they will not be significant. The choice of carriageway provision. In marginal cases, future maintenance costs may indicate that an extra lane (or hard shoulder) should be provided. Pavement strength specification. The full costs of future maintenance operations are obviously highly relevant to the choice of pavement specification Standard maintenance costs fall into two distinct categories: l Group 1 Costs - routine maintenance costs (such as drainage, lighting, boundary fencing, sweeping, gully emptying, verge cutting, sign maintenance, road markings, etc). These are expressed as costs per unit length of road and are calculated by NESA, REVS, COBA and URECA. l Group 2 Costs - works and traffic delay costs of reconstruction, overlay, resurfacing, surface dressing and patching. These are calculated externally to the economic assessment software by QUADRO It should be noted that QUADRO will not significantly af ect the benefits of new roads schemes where there is likely to be only a marginal change in traffic related maintenance or where this maintenance is unlikely to have a significant impact on road users (because, for example, diversionary routes are readily available) The maintenance cost aspects as calculated by QUADRO may have a role in the following decisions: May 1997 SH l/97 4-3

14 Volume 5 Section 1 Chapter 5 Part 4 SH l/97 Traffic and Economic Assessment in Scotland Data Sources a 5. DATA SOURCES a Central Scotland Transport Model 5.1 In March 1997, The Scottish Office appointed consultants to develop the Central Scotland Transport Model (CSTM). This model will provide the basis for most scheme assessments within its study area, details of which can be obtained from The Scottish Office. It will satisfy the requirements of complex scheme appraisals as discussed in Chapter CSTM will also provide the basis for the development of more local models where appropriate. Network Database 5.3 In conjunction with the development of the Central Scotland Transport Model, The Scottish Office is developing a network database covering the whole of Scotland. This database will hold information on available traffic data (including roadside interview data) and simplified geometric data for all links in the trunk road network. 5.4 This resource will be made available for use on scheme assessments, primarily as the starting point for the developmerit of local traffic models and for stress point analysis. 5.5 Where traffic data other than automatic count data is collected as part of a scheme assessment, copies of this data should be passed to the CSTM consultants on disk for inclusion in the network database. Scottish Road Traffic Database (SRTDb) 5.4 The SRTDb is the primary source of all automatic traffic count data and manual classified counts including rotating link census counts (counts on every link in the trunk road network carried out every six years). 5.7 The SRTDb can be accessed at The Scottish Office and all data is available for use on trunk road scheme assessments. Where automatic traffic data is collected as part of a scheme assessment, copies of this data should be passed on disk to the SRTDb manager at The Scottish Office. Road Traffic Data Collection Consultant 5.8 A consultant was appointed by The Scottish Office in April 1997 to undertake the road traffic data collection for the Central Scotland Transport Model. As part of this contract, procedures will be set up to ensure that: data collection is carried out consistently and held centrally for further use in Scotland. May 1997 SH l/97 5-1

15 l Volume 5 Section 1 Chapter 6 Part 4 SH l/97 Traffic and Economic Assessment in Scotland Reporting Procedures 6. REPORTING PROCEDURES 6.1 It is now a mandatory requirement of trunk 6.7 Scheme classification should be agreed prior road schemes costing over &lm in Scotland for to the development or selection of the traffic model the following documentation to be produced: for scheme assessment. l Scheme Classification Report Traffic Survey Report 0 l Traffic Survey Report l Local Model Validation Repot-t l Forecasting Report l Economic Appraisal Report l Traffic and Economic Evaluation Report Form 6.2 With the exception of the Scheme Classification Report, each of the above are required for each stage of scheme ussessment. However, if no further traffic survey programme or model development is undertaken after Stage 1, supplementary Traffic Survey or Local Model Validation Reports will not be required. 6.3 Details on full scheme assessment reporting (including engineering and environmental assessment reporting not covered in this Memorandum) are included in DMRB (TD 37193). 6.4 The required level of detail for each of these reporting mechanisms is both scheme and stage dependent and advice will be provided to scheme consultants by The Scottish Office if variations to the guidelines given in DMRB Volume 12 are proposed. 6.5 If considered appropriate, one or more of the reporting elements may be combined into a single document. Scheme Classification Report 6.6 A Scheme Classification Report must be produced to verify that an investigation of the kind detailed earlier has been undertaken. This will summarise the scheme s potential for induced traffic effects and will usually be of the form described in DMRB (Annex B). 6.8 A Traffic Survey Report should be produced to record all details of the traffic surveys carried out for the development of the traffic model. This should be carried out in accordance with DMRB (Appendix A). Local Model Validation Report (LMVR) 6.9 The purpose of a Local Model Validation Report is to demonstrate that the model accurately reproduces traffic movements for a selected base year through the use of observed traffic data The LMVR should present details of the network validation, trip matrix validation and assignment validation. It should distinguish between calibration and validation and identify any key issues faced during these processes The standard form of an LMVR is not appropriate for the simplest traffic appraisals. In these cases a simplified report may be prepared to describe the development of the model used for the economic assessment Comprehensive advice on LMVR preparation can be found in DMRB 12.1.l and (Appendix B). Forecasting Report 6.13 The purpose of the Forecasting Report is to document the methods and assumptions used in preparing the traffic forecasts and to present the forecasts themselves. It should contain: l a description of the methods and assumptions used in forecasting future traffic demand l a description of the Do-Minimum and Do- Something networks examined l a presentation of the Do-Minimum and Do- Something traffic forecasts May 1997 SH l/97 6-l

16 Chapter 6 Volume 5 Section I Reporting Procedures Part 4 SH l/97 Traffic and Economic Assessment in Scotland 6.14 Because the LMVR and the Forecasting Report are complementary, repetition of information should be minimised Full advice on the preparation of the Forecasting Report can be found in DMRB (Appendix C). Economic Appraisal Report (EAR) 6.16 The purpose of the Economic Appraisal Report (EAR) is to detail and justify the methodology and the data inputs and to present the results of the economic assessment. An EAR should include: plans showing the options under consideration in the local context. Plans of the Do-Nothing, Do-Minimum and all options at sufficient detail to enable link and junction details to be confirmed. a node-link diagram (showing Do-Minimum and Do-Something traffic flows) and a means of relating this to Ordnance Survey maps. a report on the inputs to the economic assessment. Where local values have been used (e.g. vehicle category proportions, M factors or E factors), the data sources should be supplied and explained as necessary. a copy of full cost estimates for each option. details of the QUADRO assessment (or reasons why no QUADRO assessment was undertaken). summary of results and conclusions including any sensitivity tests undertaken and incremental analyses of link and junction standards. full printouts from the software package(s) used, preferably appended on floppy disk No repetition of the detail contained in the Local Model Validation Report and Forecasting Report is required in the EAR. Traffic and Economic Evaluation Report Form (TEER) 6.19 A Traffic and Economic Evaluation Report form (see Appendix A) should also be completed for every scheme at each stage. This will allow a record of all traffic and economic assessment methods and results for all schemes to be held in a database at The Scottish Office The TEER form also has a vital role in the Before and After Monitoring procedures discussed in the following chapter of this Memorandum This form replaces the Appendix A form contained in the superseded SH 2/91 and should be used in Scotland in place of the form contained in Chapter 16 of the Traffic Appraisal Manual (DMRB ) Where a number of route options are being developed during Stages 1 and 2 of scheme assessment, only Part D of the form should be repeated for each option. For NESA and COBA assessments, Section C4 should also be completed unless this information is included in the Forecasting Report Jt should be noted that NESA and REVS produce much of the TEER form information automatically as output. Also, copies of the form are available on disk from The Scottish OfFme since this is the preferred method of data transfer Completed TEER forms should be provided in 3% disk format to The Scottish OfFme s Traffic Advisors (SIAS Ltd., 37 Manor Place, Edinburgh EH3 7EB) for inclusion in the traffic and economic assessment database and copied to The Scottish Office for information. The Scottish Office s Traffic Advisors 6.25 The Scottish Oftice has appointed two consultants as Traffic Advisors to provide an auditing role on all scheme assessments which involve significant traffic and economic assessments For a full listing of contents to be included in the EAR, refer to DMRB SH l/97 May 1997

17 Volume 5 Section 1 Chapter 6 Part 4 SH l/97 Traffic and Economic Assessment in Scotland Reporting Procedures 6.26 Each traffic and economic assessment report prepared by a Consulting Engineer or Local Authority will therefore be audited by The Scottish Office s Traffic Advisors. This will involve an audit of the traffic or transport model and its use during the scheme assessment. Data Storage Requirements 6.28 Consulting Engineers and Local Authorities should store all input data, assessment outputs and any other relevant material until directed otherwise by The Scottish Office The Traffic Advisor will review the traffic and economic elements of the Inception Report and review documents prior to the completion of each stage of scheme assessment. May 1997 SH l/97 6-3

18 Volume S Section 1 Chapter 7 Part 4 SH l/97 Traffic and Economic Assessment in Scotland Before and A,fter Monitoring 0 7. BEFORE AND AFTER MONITORING General 7.1 The Scottish Office operates a system of Before and After Monitoring for all schemes costing qver Elm which compares the traffic flows resulting from the implementation of a trunk road scheme with those predicted during the scheme s preparation. 7.2 To facilitate these comparisons, The Scottish Office has set up a standard reporting system for recording the forecast traffic flows, the methods utilised in determining these forecasts and for collecting and reporting the traffic counts taken after the scheme has opened. The aims of this procedure are: l to satisfy the demands of good management and public accountability by providing the answers to questions about the effect of a new or improved road, l to identify the strengths and weaknesses in the techniques used for appraising schemes, so that confidence in the roads programme is maintained, l to allow the predictive ability of the traffic or transport models used to be monitored to establish whether any particular form of model is consistently more reliable than others when applied to particular types of schemes, and l to assist in the compensation under Part 1 of the Land Compensation (Scotland) Act 1973 for depreciation due to the physical factors caused by the use of public works. 7.3 Further guidance on The Scottish Office s Before and After Monitoring procedures will be provided in due course. May 1997 SH l/97 7-l

19 VoLune 5 Section 1 Chapter 8 Part 4 SH l/97 Traffic and Economic Assessment in Scotland References e 8. REFERENCES DMRB Volume 5 DMRB Volume 6 Assessment and Preparation of Road Schemes Road Geometry DMRB Volume 11 Environmental Assessment DMRB Volume 12 Traffic Appraisal of Road Schemes (including the Traffic Appraisal Manual, Traffic Appraisal in Urban Areas and [educed Traffic Appraisal) DMRB Volume 13 Economic Assessment of Road Schemes (the COBA Manual) DMRB Volume 14 Economic Assessment of Road Maintenance (the QUADRO Manual) l DMRB Volume 15 Economic Assessment of Road Schemes in Scotland (the NESA Manual) Trunk Roads and the Generation of Traffic (HMSO, 1994) Economic Appraisal in Central Government - A Technical Guide for Government Departments (Stationery Office, 1997) The URECA Manual (Department of Transport, 1996) May 1997 SH l/97 8-l

20 l Volume 5 Section 1 Chapter 9 Part 4 SH l/97 Traffic and Economic Assessment in Scotland Enquiries 9. ENQUIRIES Approval of this document for publication is given by the undersigned: Deputy Chief Engineer The Scottish Office Development National Roads Directorate Victoria Quay EDINBURGH EH6 6QQ Department J HOWISON Deputy Chief Engineer All technical enquiries or comments about tlhis publication should be sent in writing to the above. May1997 SH l/97 9-l

21 Volume 5 Section 1 Part 4 SH l/97 Traffic and Economic Assessment in Scotland Appendix A TEER Form A. TRAFFIC AND ECONOMIC EVALUATION REPORT FORM National Roads Directorate Scottish Office Development Department Victoria Quay EDINNUURGH EH6 6QQ Tel: Fax: Part A - General Information Al. Project Details Route Number(s) Project Title Scheme Location (including OSGR): Study carried out by A2. Stage of Scheme Preparation Reached (see DMRB 5.1.2) Preliminary Assessment (Stage 1) Post Tender Post Construction A3. Traffic and Economic Reporting to Date (see DMRB ) Report Title Date ol Fina1 Report A4. Network Classification and Proposed Level of Provision: Network Classification 1 Road Standard (km) 1 Number of Junctions I (see DMRB ) Urban I Single 2 lane I Grade Separated I Inter-Urban Local Climbing Lane Roundabouts Inter-Urban General Inter-Urban Tourist Rural Local Rural General Rural Tourist Wide Single 2 lane Dual 2/3 lane All Purpose Dual 2/3 lane Motorway Other (Please Specify) Priority Traffic Signals Other (Plcase Specify) May 1997 SH l/97 A-l

22 Appendix A TEER Form Volume 5 Section 1 Part 4 SH l/97 Traffic and Economic Assessment in Scotland A5 Nature of the proposed scheme: Improvement on existing line km Improvement on new alignment km Bypass km New Route km Junction Improvement km Other (Please Specify): km Total Length of Scheme km Is the scheme isolated, or part of a larger improvement? (please specify) Part B - Calibration and Validation of the Traffic Model El. Model Base: Year Traffic Flow Units (e.g. pcus/vehicles, AAWDT) Modelled Time Period(s) B2. Size of Model (Calibration Base) pzjq=l Number of Modelled Junctions Please ensure the Local Model Validation Report contains a network diagram showing numbered links and nodes, for both base and design networks. B3. Model Trip Database Please list those counts used to derive the base-year matrices (as detailed in Traffic Survey Report). Survey Type Number Date(s) of Survey Junction Counts Link Count Only Commercial Vehicle Survey Postcard Questionnaires Household lnterviews A-2 SH l/97 May 1997

23 Volume 5 Section 1 Part 4 SH l/97 Traffic and Economic Assessment in Scotland Appendix A TEER Form B4. Details of sub-models used: Traffic Assignment Model (name and version of modelling including any sub-models) Trio End Model Trip Distribution Model Mode Choice Model Other (Please specify) suite, B5. Details of road network speed coding (please tick relevant coding):- I Speed/flow curves validated to observedjourney times I I (please give details) NESA Default Link Speeds (see DMRB ) Other (Please specify): B6. Trip Matrices If NESA is used, are IJser Classes 1 to 15 (see DMRB ) input as single all vehicle matrix? Yes/No If No and for other programs than NESA, please state number of matrices and detarl mput matrix data composition: Matrix Time Vehicle Type/Trip Purpose Base Year Matrix Totals Number Period (NESA User Classes) (pcu/vchicles) 1 (continue if necessary) B7. Flow Group Deiinition (see DMRB ) [NESA and COBA only] Flow Group FGI FG2 FG3 FG4 FC5 (optional) FG6 (optional) Number of I-lours Representative Time Period (where appropriate) May 1997 A-3

24 Volume 5 Section 1 Part 4 SH l/97 Traffic and Economic Assessment in Scotland BS. Vehicle Category Proportions (see DMRB ) Please detail vehicle category proportions for the Calibration Base matrix. The source of these proportions should be detailed in the Economic Assessment Reporl. Flow Group or Time Period Car LGV OGVl OGV2 Coach I I I I I I I (expand ifnecessary) PCU Factor(s) (where appropriate): B9. Matrix Estimation Technique used (see DMRB ): Link and Junction Count only Observed Matrix Synthetic Matrix (give details below) Partial Matrix (give details below) Combination of Observed and Synthetic (give details below) Other (Please specify): Further Details (including software used): BlO. Assignment Details Matrix Generalised Cost Equation(s) 1. All Vehicle 2. Other (Please specify) Assignment Method e.g. All or Nothing, Multi-routejng, etc. Was any fitting of route choice parameters undertaken? Yes/No For NESA Analyses: Number of trees built = Value of P (multi-routeing parameter) = Mode Choice Was modal competition If Yes please specify:- assessed? YES/NO B12. Values of any other factors or parameters where defaults are not used and/or further details regarding the traffic model A-4 SH II97 May 1997

25 Volume 5 Section 1 Appendix A Part 4 SH l/97 Traffic and Economic Assessment in Scotland TEER Form B13. Network Checks Please identify which of the following have been undertaken and ensure that details are given in the Local Model Validation Report. B14. Assignment Checks Plcase identify which of the following have been undertaken and ensure that details are given in the Local Model Validation Report. 1 Route checking from selected zones I I 1 Link snceds checked against iournev time survey results I I Overtaking rate cheeks [REVS only] Assigned flow comparisons with traffic counts for model calibration? Assigned flow comparisons with independent traffic counts for model validation? Over-Capacity Links and Junctions List over-capacity links and junction nodes in the Calibration l3asc (base year): Year Link/Junction Node Flow Group or Ratio of Flow (including location) Time Period to Capacity (extend icneccssary) B15. Present Year Validation Is model base year more than three years earlier than the current year? If YES has a Present Year validation been undertaken? Yes/No Yes/No Part C - Traffic Forecasting Cl. Do-Minimum Assumptions Plcase identilk schemes, policies or measures assumed to be in place before opening year: May 1997 SH l/97 A-5

26 Appendix A Volume 5 Section 1 TEER Form Part 4 SH l/97 Traffic and Economic Assessment in Scotland c2. Traffic Growth: Please indicate the type of growth factors used (if any) and the manner in which they were applied: Growth Factor J Description (set DMRB ) (e.g. NRTF applied to commercial vehicle matrix) NRTF Local Planning and TEMPRO Data Other (Please Specify) Were any growth constraint techniques (see DMRB I Appendix G) used?: IFYes, please indicate the precise technique below: Yes/No Growth Constraint Techniques J User determined factors or cut-offs Matrix Capping Techniques Elasticity Techniques Incremental Loading Techniques Shadow Network Techniques Other (Please Soecifv) I-lave local developments been considered (outwith any planning data input)? Yes/No Were Variable Trip Matrices used? If YES, please specify methodology c3. Forecast Years Opening Year(s) Design Year(s) Forecast Years used: Yes/No c4. Over-Capacity Links and Junctions [NESA and COBA only] List over-capacity links and junction nodes (for both Do-Minimum and Do-Something networks, low and high growth, opening and design years): Year Link/Junction Node (including location) Network (DMIDS) Growth Scenario (low/high) Flow Group or Time Period Ratio of Flow to Capacity (extend if necessary) A-6 SH 1197 May 1997

27 Volume 5 Section 1 Appendix A Part 4 SH I/97 Traffic and Economic Assessment in Scotland TEER Form Part D - Economic Assessment Dl. Economic Assessment Details Program Used Version Date 0 f runs Variable or Fixed Trip Matrix Analysis D2. Design Scheme Costs (gm) Route Option (e.g. preferred lint) Capital Cost of Scheme Year and Month of Estimate Retail Price Index Relative Price Factor (ifuscd) Capital Cost in mid prices discounted to 1994 ILm) Capital Cost Profile D3. Base Network Costs (if appropriate) (see DMRB ) Year 1 Cost ( Base Network Improvement (list items) I I Year and Month of Estimates Retail Price Index Relative Price Factor (if used) Base Network Costs in mid arices discounted to 1994 (Lm) I I D4. Traffic Flow Conversion Factors (see DMRB x ) (where appropriate) Please ensure that derivation of factors is contained in the Economic Assessment Report (see DMRB ). If factors vary throughout the evaluation period, please specify. May 1997 SH 1197 A-7

28 Appendix A Volume 5 Section 1 TEER Form Part 4 SH l/97 Traffic and Economic Assessment in Scotland D5. Traffic Modelling Input Please indicate the forecast years for which trarfic flow data is input to the economic assessment (see DMRB ). For standard NESA and COBA assessments, only the hase year is input but note that NESA and COBA allow future year traffic flows to he input (see DMRB 15.1 S.6). (extend if necessary) Where a traffic assignment model other than NESA has been used, has a sub-area of the model been used for the economic assessment? Yes/No I-low many junclions were included in the economic assessment?,.,...junclions What is the maximum junction delay cut off (see DMRB 15.1.X.4) PESA, COBA and URECA only]?.,.. sets Please ensure that relevant details of the traffic modelling details of convergence statistics where appropriate. are contained in the Economic Assessment Report, particularly D6. Car-In-Work Time Proportions (see DMRB ) Please detail Car-in-Work Time proportions. The source of these proportions should be detailed in the Economic Assessment Repoti. Flow Group or Car-In-Work Time Time Period Proootiions (expand if necessary) D7. Comparison Between Coded and Calculated Link Speeds [NESA and COBA Only] List rural and motorway links where coded and calculated light vehicle speeds differ by more than 20 kph and urban links where they differ by more than lokph (for both Do-Minimum and Do-Something networks, low and high growth, opening and de&n years): Year Link (including location) Rural or Network Growth Scenario Urban (DM/DS) (High/Low) Flow Group or Time Period Coded Speed (W) Calculated Speed (WI (extend if necessary) A-8

29 Volume 5 Section 1 Appendix A Part 4 SH I /97 Traffic and Economic Assessment in Scotland TEER Form DS. Accidents Please indicate the source of accident rates and costs: Please ensure that details ofthe accident modelling arc contained in the Economic Assessment Reporl D9. Annual Costs The following design year): table should be completed for the scheme opening year and at lcast one other forecast year (preferably the Accidents (as appropriate) DlO. Rates of Return Scheme Year Rate ol Keturn Scheme Year Rate of Return Scheme Rate of Rctum 1 LOW HIGJ-J ( 1 LOW HIGH May 1997 SH l/97 A-9

30 Appendix A TEER Form Part 4 SH l/97 Traffic and Economic Volume 5 Section 1 Assessment in Scotland Dll. Summary of Costs and Benefits from Economic Assessment All costs arc discounted to 1994 values (at 6%) and expressed al mid-1994 PhCL-S. prices (RPI = 144.1) in Em s to two decimal (NPV = IWB - PVC) BCR (PVWPVC) D12. Audit Procedures Name Dale Form completed by Prqject Design Division Completed Database Entry Audit Printout Received? YES/NO If YES, location: A-10 SH l/97 May 1997