Highways Agency

Safe roads, Reliable journeys, Informed travellers

Contents

A43 Silverstone Bypass

1. Introduction
   • Background
   • Scheme Objectives
   • Purpose of the Report
2. Data Collection and Evaluation
   • Data Collection
   • Summary of Results
   • Traffic Growth
   • Journey Times
   • Journey Speeds
3. POPE Methodology
   • Introduction
   • Vehicle Hour Benefits
   • Changes in Link Transit Time
   • Changes In Accident Benefits
   • Summary of POPE Methodology
4. Economic Benefits of the Two Schemes
   • Introduction
   • COBA Re-evaluation
   • Comparison of POPE and COBA Methodology
   • Re-Evaluation of Scheme Costs
5. Evaluation Summary Table
   • Introduction
   • Appraisal Summary Tables (AST)
   • Outturn Effects
6. Summary of Conclusions

• Annex A - Traffic Volumes over the F1 Weekend (570KB PDF)

1. Introduction

BACKGROUND

1.1 The A43 (T) Silverstone and Whitfield Turn to Brackley Hatch (Syresham bypass) improvement schemes officially opened on the 18th September 2002, providing an improved route for through traffic using the A43 between the M40 and M1 and for regional movements between Brackley and Towcester, Northamptonshire. The location of the improvements in the wider regional context is illustrated in Figure 1.1 below. The opening of these combined schemes provided a continuous dual carriageway between the M40 and A5. They comprise two sections of new dual carriageway, bypassing the villages of Silverstone and Syresham, as well as widening of the remaining single carriageway sections.

1.2 Also shown on Figure 1.1 is the M40 to B4031 Improvement scheme undertaken by the Highways Agency, which was completed in February 2002. As this Report focuses on the effects of the two more recent improvement schemes, the traffic volumes for the ‘Before’ situation have been taken post February 2002, and thus include the effects of the M40-B4031 scheme.

Figure 1.1 – A43 improvement schemes

1.3 Figure 1.2 below shows the completed scheme in more detail.

Figure 1.2 – Silverstone and Syresham bypass

1.4 In order to assess the immediate responses to the new scheme, ‘Before’ and ‘After’ traffic volume data on the A43 and other competing routes was collected immediately prior to and after opening in September 2002 to monitor the effects of the new scheme.

1.5 In addition, traffic data from surveys on County roads from Northamptonshire County Council and existing Highways Agency permanent count sites was obtained to evaluate the effects of the opening of the A43 (T) Silverstone and Syresham bypasses on strategic traffic routeing patterns in the area and the effects of this immediate response to the improvements was reported in the Traffic Impact Study Report.

SCHEME OBJECTIVES

1.6 The A43 improvements are made up of two named schemes within the Highways Agency’s Road Programme called the Targeted Programme of Improvements (TPI), namely:

• A43 Silverstone (8kms); and
• A43 Whitfield Turn to Brackley Hatch (4.6kms), which we have termed the A43 Syresham Bypass for the purpose of this Report.

1.7 These schemes were implemented to address the following problems, which are listed within the scheme Appraisal Summary Tables (AST). These problems were:

Silverstone section

• Serious environmental, safety and journey time reliability problems in Silverstone village; and
• Part of a scheme to complete dualling of important A43 link between M40 and M1.

Syresham Section

• Large journey reliability and safety problems along route and in small communities of Pimlico and Syresham; and
• Part of a scheme to complete dualling of important A43 link between M40 and M1.

PURPOSE OF THE REPORT

1.8 This report represents the ‘One-Year After’ report for the A43 improvement schemes. This report has been prepared as part of the Post Opening Project Evaluation (POPE) Commission and builds on the Traffic Impact Study (TIS) report prepared for the Highways Agency in December 2002.

1.9 This report will set out a number of assessments, namely:

• A comparison of the "Before" and "After" traffic volumes on the A43 and other roads in the corridor and illustrate how traffic volumes have changed since the opening of the A43 improvements;
• A comparison of "Before" and "After" journey times on the A43;
• It will also present an evaluation of predicted and outturn economic forecasts based on changes in journey times as well as other outturn effects in the form of an Evaluation Summary Table (EST); and
• The report will also outline the changes in accidents on the route and whether they have changed since the opening of the A43 schemes.

1.10 This report specifically considers the re-evaluation of the predicted benefits for the A43 improvements including the Silverstone and Syresham bypasses. The three main elements involved are:

• To identify the costs and benefits originally forecast for the scheme at Order Publication Report (OPR) stage;
• To quantify the outturn (actual) costs and the outturn level of benefits actually accruing, based on outturn traffic volume and journey time data for the scheme; and
• To compare the results and quantify the difference in the Present Value of Benefits (PVB).

1.11 Following this introduction the report has been divided into five further sections as follows:

• Section 2 outlines existing data collation and new data collection and reports on traffic volume and journey time changes attributable to the A43 improvements;
• Section 3 presents an assessment of predicted and outturn economic benefits using the POPE journey time methodology;
• Section 4 presents the original economic results, calculated by the Department for Transport"s program COBA for these schemes and the level of benefits that would have been forecast if outturn traffic volumes and journey times were known at the time. The section also compares the COBA and POPE methodology;
• Section 5 presents the original Appraisal Summary Tables (AST) for the A43 Silverstone and Syresham Bypasses, which were completed as two separate exercises and then re-evaluates these predictions within an Evaluation Summary Table (EST). The section also gives an early indication of changes in the number of accidents in the corridor;
• Section 6 summarises the main conclusions from the evaluations and the limitations to use; and finally
• In Annex A, we also present an indication of traffic volume changes during the Formula 1 Grand Prix Weekend, held in July 2003.

1.12 It should be noted, that the ‘One-Year After’ report is primarily focused on the evaluation of Economy and Safety sub-objectives of the GOMMMS Appraisal. Environmental evaluation has not been carried out at this stage, but will form part of the ‘5-Year After’ evaluation.

2. Data Collection and Evaluation

DATA COLLECTION

2.1 This One Year ‘After’ Report for the A43 (T), M40 to A5 Dualling, includes the following surveys:

‘Before’ Surveys

• 2 Automatic Traffic Count (ATC) surveys on the A43;
• 4 ATC surveys by Atkins on behalf of Northamptonshire County Council;
• Traffic data from 6 Highways Agency permanent count site locations; and
• Journey time surveys on A43 (T) from M40 to the A5 at Towcester.

‘After’ Surveys

• For the ‘After’ surveys, the above surveys were re-assessed, plus two additional ATC surveys on the new A43 bypass sections, which were counted in the first month after opening as well as one-year after opening.

2.2 The details of the ‘Before’ and ‘After’ surveys (with OSGR’s for site locations) are described below.

Automatic Traffic Counts

2.3 Atkins undertook automatic traffic count (ATC) surveys in September 2002 and September 2003 at the following six locations, as illustrated in Figure 2.1:

• Old A43 Brackley Road (Silverstone village) - (4672, 2447);
• Old A43 Main Road (north of Syresham village) - (4636, 2414);
• New A43 Silverstone Bypass (south of A413 junction) - (4683, 2458);
• New A43 Whitfield Turn to Brackley Hatch Dualling (Green Man junction) - (4645, 2415);
• M40, North of Junction 10 - (4490, 2357); and
• M40, South of Junction 10 - (4548, 2245).

2.4 Traffic data from surveys undertaken by Atkins on behalf of Northamptonshire County Council to monitor the effects of the scheme opening on other routes in Northamptonshire and data from permanent Highways Agency count sites was also obtained to ensure a comprehensive evaluation of any strategic traffic routeing changes in Northamptonshire.

2.5 The County sites are as follows (and illustrated in Figure 2.1):

• B4525 at Falcut (alternative to A422 from J11 of M40 (Banbury)) - (4597, 2424);
• A361 at Byfield (route from J11 of M40 to Daventry) - (4516, 2527);
• A422 at Deanshanger (route from Buckingham joining A5 west of Milton Keynes) - (4776, 2403); and
• A413 at Lillingstone Dayrell (route from Buckingham to A43 south of Towcester) - (4701, 2399).

2.6 Traffic data was also obtained from Highways Agency permanent count sites on trunk roads (as shown in Figure 2.1), namely;

• A43 at Whitfield (south west of scheme) - (4595, 2388);
• A43 at Blisworth (north east of Towcester) - (4725, 2563); and
• Two locations on the A5 at Pattishall and Alderton (north and south east of Towcester) - (4661, 2551) and (4705, 2475).

Journey Time Surveys

2.7 Journey time surveys were undertaken on the A43 (T) between the junction 10 of the M40 and A5 at Towcester. The surveys covered the full A43 (T) M40 - A5 Dualling Scheme, which includes the M40 to B4031 (A421) improvement (dualling of existing single carriageway road) which was completed in February 2002. The survey route, comprising five timing points, is depicted in Figure 2.2.

2.8 ‘Before’ journey time surveys previously undertaken in September 2002 were used for comparison with surveys carried out post scheme opening. Survey periods were the morning (07:30 – 09:00) and evening (16:30 - 18:00) peaks as well as an interpeak period (10:00 -11:30).

Figure 2.2 – Journey Time Survey Route from M40 to A5

SUMMARY OF RESULTS

Traffic Volume Changes

2.9 Figure 2.3 below shows the changes in daily traffic volumes on the A43 and other roads in the area. All ‘Before’ traffic volumes have been factored up to reflect September 2003 traffic levels to ensure the conclusions drawn take into account seasonality and normal traffic growth.

Figure 2.3 –Traffic Volume Changes around Silverstone and Syresham

2.10 The main points to note for traffic volume changes on the A43 are:

• The traffic volume data collected as part of this Study demonstrates that the A43 (T) around Syresham / Silverstone carried 27,000 - 28,000 vehicles per day (vpd) in September 2002, before opening, which increased to around 28,000 - 30,000 vpd (on an average weekday) just after opening;
• A year after opening the traffic on the bypass has risen to around 35,000 vpd at Syresham, an increase of around 20%, and 34,000 vpd at Silverstone, an increase of around 17%;
• This level of growth is above the normal increase in traffic flow, and thus it seems likely that the A43 (T) scheme has drawn additional traffic into the corridor, mainly from parallel routes in Northamptonshire to take advantage of time savings on the improved A43 route between the M40 and A5 at Towcester;
• Traffic volumes on the old route in Syresham and Silverstone show a significant change after the opening of the improvement schemes. The Before traffic volumes of 27,000 - 28,000 vpd reduce to around 500 vpd in Syresham (a 96% reduction) and 2,800 vpd in Silverstone (a 90% reduction), clearly indicating that the scheme has been successful in routeing vehicles away from these villages;
• Traffic volumes from the Highways Agency permanent count sites on the A43 at Whitfield to the South West of the Scheme and Blisworth to the North East of the scheme also demonstrate a significant increase in traffic volumes from the "before" situation. At Whitfield, traffic volumes have increased from 24,900 vpd to 33,100 vpd, an increase of 33%, and at Blisworth, north of the A5, traffic volumes have increased from 31,600 vpd to 37,400 vpd, an increase of 18%.

2.11 These increases on the A43 are explained by traffic changes elsewhere, namely:

• Figure 2.3 shows that daily traffic volumes have decreased on the M40, north of Junction 10, the A43 junction. North of Junction 10, traffic volumes have reduced from 96,900 vpd in September 2002 to 90,800 vpd post-opening, a reduction of 6,100 vpd. South of the A43 junction on the M40, traffic volumes remain largely unchanged at just over 112,000 vpd suggesting that traffic is rerouting from the M40 onto the A43 and M1, for longer distance north south movements;
• There is a reduction of 700 trips on the A361 at Byfield, where traffic volumes reduce by 8% from 8,200 vpd to 7,500 vpd. These changes suggest a re-routing of traffic from the A361 to the A5 and A43;
• Similarly to the South East of the scheme, traffic volume reductions are observed on the A422, south of the A5, where traffic volumes reduce from 14,900 vpd to 13,700 vpd, a decrease of 1,200 vpd, or 8%;
• These three changes suggest an 8,000 increase on the A43 and this is the level of increase shown on the A43 north of Brackley. Thus, these figures suggest that there has been a re-assignment of traffic from these three routes onto the A43.
• Daily traffic volumes on the B4525 are also showing an increase following scheme opening. Immediately after scheme opening traffic volumes rose from 2,650 vpd to 3,440 vpd, an increase of 790 vpd, which represents a 30% increase in daily traffic. One year after opening the daily traffic volumes on this road are shown to increase further to 3,790 vpd, a 43% increase. This is most likely related to the improvement in turning opportunities at the B4525 junction with both the old A43 (where traffic volumes on the old road are very much reduced) and with the new A43 (where a free flowing junction is now provided);
• This 1,200 vpd increase also explains why the A43 north of Silverstone is only showing increases of around 6,000 vpd, compared to 8,000 vpd further south of Brackley; and
• No change in traffic volumes are recorded on the A413 at Whittlebury, south of the A43 nor on the A5 south of Towcester.

TRAFFIC GROWTH

2.12 Figure 2.4 below shows the monthly variation in traffic, on the A43 at Brackley from January 2002 to December 2003. The timing of the A43 improvement schemes is also shown and clearly the step change in traffic volumes after scheme opening is immediately apparent. Comparing January-August 2002 with January-August 2003, there is an increase of 35% in traffic volumes over the two periods.

Figure 2.4 – Monthly Variation in Traffic Flows on the A43 at Brackley

2.13 This section of A43 is obviously adjacent to the Silverstone Motor Racing Circuit. As traffic volumes are continually monitored in this area, Annex A contains a section on traffic volumes on the A43 during the F1 weekend and compares these traffic volumes with non-race weeks to identify changes and trends.

2.14 It is also important to note that the scheme has not only been beneficial for the F1 weekend but for other events held at the circuit including Superbikes and Grand Touring cars. The Silverstone Motor Racing Circuit is used for events on most weekends of the summer, and the improvement has facilitated easier access to these events.

JOURNEY TIMES

2.15 Journey Time surveys were undertaken on the A43 (T) between Junction 10 of the M40 and A5 at Towcester for both the ‘before’ situation and after the A43 was improved.

2.16 The surveys covered the full A43 (T) M40 - A5 Dualling Scheme, which includes the M40 to B4031/A421 improvement (dualling of existing single carriageway road) south of Brackley, which was completed in February 2002. Survey periods were the morning (07:30 – 09:00) and evening (16:30 - 18:00) peaks as well as an inter-peak period (10:00 -11:30).

2.17 The ‘before’ and ‘after’ survey periods were September 2002 and September 2003 respectively, and thus the time savings shown reflect the completion of the Silverstone and Syresham improvements on this section of A43. The survey route is depicted in Figure 2.2.

2.18 The Journey Time Survey results are shown in Table 2.1 below.

Table 2.1 – Journey Times along the A43 between the M40 and A5

Direction	Period	Journey Time (Mins)
		Before (Sept 02)	After (Sept 02)	1 Year After (Sept 03)	Saving (Before & 1- year after)
Northbound	AM	26:18	18:38	18:55	07:23
	Inter	25:25	17:44	18:55	06:30
	PM	28:53	20:57	19:42	09:11
Southbound	AM	29:07	18:37	19:01	10:06
	Inter	26:25	17:44	18:53	07:32
	PM	28:45	19:27	19:25	09:20

2.19 From the Journey Time data it is suggested that initial time savings in the weeks after opening were up to 10 minutes, and these levels of time savings have been sustained one-year after opening.

2.20 There is also a significant improvement in the variability of the Journey Times. Before the two schemes opened, there was around a 3 minute time difference between the AM and Inter peak in the southbound direction, but the ‘after’ times are very consistent between all time periods and for both directions, thus the journey time reliability is very much improved.

JOURNEY SPEEDS

2.21 Table 2.2 below compares the Journey Speeds ‘Before’, ‘After’ and ‘One Year After’ scheme opening. Average speeds on the new A43 bypass are up to 20 - 27 kph faster a year after scheme opening, and journey speeds are very consistent at around 86 kph, thus confirming the improvement in journey reliability; and implying that free flow is being achieved in all time periods and in both directions.

Table 2.2 - Journey Speeds along the A43 between the M40 and A5

Direction	Period	Journey Speeds (kph)
		Before (Sept 02)	After (Sept 02)	1 Year After (Sept 03)	Saving (Before & 1- year after)
Northbound	AM	62	87	86	24
	Inter	64	92	86	22
	PM	56	78	83	27
Southbound	AM	56	87	86	20
	Inter	62	92	86	24
	PM	57	84	84	27

3. POPE Methodology

INTRODUCTION

3.1 As part of this ‘One-Year’ After Study, the Report is also assessing the predicted level of economic benefits. This section assesses the level of economic benefits predicted for each of the two A43 schemes and compares these predictions with actual benefits accrued when considering actual traffic volume changes and actual journey time benefits.

3.2 Two evaluations have been undertaken, one for the 8km Silverstone section, and one for the 4.6km Whitfield Turn to Brackley Hatch (Syresham) section. These have been evaluated separately as the original appraisals were also undertaken separately.

3.3 The approach that we have taken is termed the Post Opening Project Evaluation (POPE) methodology. The basis of the POPE methodology is that through previous COBA evaluations undertaken it has been identified that the majority of benefits are derived primarily from two areas:

• Link Transit time (vehicle hours) benefits; and
• Accident Benefits.

3.4 As such, link transit time, (which is represented by traffic volumes multiplied by journey times) and the number of accidents can be collected before and after scheme opening and the difference between these observed values can be compared to the difference shown in time and accidents for the same links shown in the OPR COBA’s. The premise of the POPE methodology is that the change in the observed flows, times and accidents can be directly associated to the economic benefits predicted for this scheme.

3.5 The following section outlines this approach in more detail.

VEHICLE HOUR BENEFITS

3.6 To calculate link transit time or vehicle hour benefits, the COBA deck from OPR must be available, and the following changes implemented so that sensible and like-for-like comparisons can be made:

• OPR - Do Minimum: Although flow and delay data was probably collected prior to scheme implementation at the OPR stage, journey time and delay information must be determined by re-running the COBA deck with a journey time year set to the same as that when the Post Opening surveys were undertaken;
• OPR - Do Something: As with the OPR Do Minimum this data will need to be determined from re-running the COBA deck for the survey year after opening;
• Actual - Do Minimum: Pre opening count and Journey Time data is collected for each new scheme route before opening. This information is obtained for the AM, IP and PM time periods; and
• Actual - Do Something: Traffic volumes and journey times from surveys after the opening of the schemes are directly applicable to this scenario.

3.7 In considering the changes between the OPR COBA and the observed vehicle hour benefits, we are limited by the availability of data. Only peak hour and off peak hour journey times are available for the key links before and after opening, even though count data has been collated for the whole 24 hour period.

3.8 This means that only the bypass and bypassed links (where data IS available) are considered in the POPE assessment, and thus the change in vehicle hours can be compared with the change in link transit time for the same links in the OPR COBA.

3.9 This test assumes that flow data, on key links, is available by hour for a 24 hour period and journey time data is only available for the peak and off peaks.

3.10 This means that expansion factors from peak hour to peak period and off peak period to all other hours have been calculated from the Do Minimum observed flow data. This has then been used to factor up the outturn data to a total average day.

CHANGES IN LINK TRANSIT TIME

3.11 Tables 3.1 and 3.2 below show the differences between the vehicle hours before and after opening of the bypasses (observed traffic volumes multiplied by times) and the differences between flow x times for the same links in the OPR COBA.

Table 3.1 - Comparison of Vehicle hours for Silverstone along the bypass and bypassed links

Total Vehicle-Hours per year
		Low Growth	High Growth
OPR COBA	DM	740400	880826
	DS	635441	733533
	Difference	104959	147293
Observed	‘Before'	1066336	1066336
	‘After'	858976	858976
	Difference	207360	207360

Table 3.2 - Comparison of Vehicle hours for Syresham along the bypass and bypassed links

Total Vehicle-Hours per year
		Low Growth	High Growth
OPR COBA	DM	437693	499036
	DS	344270	385523
	Difference	93423	113513
Observed	‘Before'	716811	716811
	‘After'	521456	521456
	Difference	195355	195355

3.12 Table 3.1 shows that the saving in observed vehicle hours for the Silverstone schemes is 207,000 hours over the year. For the same links and scheme year, the Low Growth prediction was 105,000. The OPR COBA assessment showed that the Link Transit Time benefits for this scheme were £12.910 million.

3.13 This means that 105,000 vehicle hour saving correlates to £12.9 million of benefits, and using the same relationship between vehicle hours saved and economic benefit, the observed 207,000 hours saved correlates to £25.5 million benefits. Thus, the outturn benefits are estimated to be almost double what was predicted.

Table 3.3 – Link Transit Time benefits for Silverstone

Difference in VehicleHours for Silverstone
	OPR stage		Actual
	Difference	Link Transit Time Benefits	Difference	Predicted Benefit
Low Growth	104,959	£12.910m	207,360	£25.505m
High Growth	147,293	£25.319m	207,360	£35.644m

Table 3.4 – Link Transit Time benefits for Syresham

Difference in VehicleHours for Silverstone
	OPR stage		Actual
	Difference	Link Transit Time Benefits	Difference	Predicted Benefit
Low Growth	93,423	£4.268m	195,355	£8.925m
High Growth	113,513	£8.003m	195,355	£13.773m

3.14 Tables 3.3 and 3.4 summarise the POPE estimate of benefits for both Low and High Growth for the Silverstone and Syresham Improvement schemes, and shows:

• Silverstone Low Growth - outturn benefits are estimated to be £25.5m, which are 98% higher than those predicted;
• Silverstone High Growth - outturn benefits are estimated to be £35.6m, 40% higher than originally forecast;
• Syresham Low Growth - outturn benefits are estimated to be £8.9m, more than double that originally forecast, and
• Syresham High Growth - outturn benefits of £13.8m, which is over 70% higher than originally forecast.

3.15 It was normal at the time of the OPR assessment for Low and High Growth to be weighted to create an average cost, by utilising 60% of the Low Growth result, and 40% of the High Growth Result. We have retained this assumption when considering weighted growth in this report. Thus, the POPE comparison suggests:

	Predicted Benefits £m	POPE Outturn Benefits £m	% Increase £m
Silverstone Section	17.9	29.6	65%
Syresham Section	5.8	10.9	85%

3.16 Thus, the actual time benefits for the Silverstone scheme are around 65% higher than those originally forecast, and around 85% higher than forecast for the Syresham section.

CHANGES IN ACCIDENT BENEFITS

3.17 Table 3.6 below shows the difference between the actual number of accidents before and after opening of both bypasses and the difference between the number of accidents predicted by COBA.

Table 3.6 – Comparison of actual and predicted number of accidents at Silverstone and Syresham along the bypass and bypassed links

Total Number of accidents per year
		Low Growth	High Growth
OPR COBA	DM	49	55
	DS	19	21
	Saving	30	34
	(reduction)	(61%)	(62%)
Actual	‘Before’	46	46
	‘After’	28	28
	Saving	18	18
	(reduction)	(39%)	(39%)

3.18 COBA has predicted a saving of 30 accidents, for low growth, whereas the actual saving, along the same links and scheme year, is only 18 accidents.

3.19 The OPR COBA assessment showed that the Accident Benefits were £15.082 million, at low growth. This means that 30 accidents saved correlates to £15.1 million of benefits, and using the same relationship between accidents saved and economic benefit, the observed saving of 18 accidents equates to £9 million benefits. Thus, the outturn benefits are estimated to be only 60% of what was predicted.

Table 3.7 – Accident Benefits at Silverstone and Syresham

Accident saving at Silverstone and Syresham
	OPR stage		Actual
	Difference	Accident Benefit	Difference	Predicted Benefit
Low Growth	30	£15.082m	18	£9.049m
High Growth	34	£22.561m	18	£11.944m

3.20 Table 3.7 above summarises the POPE estimate of benefits for both Low and High Growth for the Silverstone and Syresham Improvement schemes, and shows:

• Low Growth - outturn benefits are estimated to be £9.049m, which are 40% lower than those predicted;
• High Growth - outturn benefits are estimated to be £11.944m, which are 53% lower than those predicted;

3.21 The weighted benefit is 44% lower than that was originally forecast, as shown in Table 3.8 below.

Table 3.8 – Comparison of POPE Outturn and Predicted Accident Benefits

	&OPR Predicted Benefits £m	POPE Outturn Benefits £m	% decrease £m
Improvement Scheme	18.1	10.2	44%

SUMMARY OF POPE METHODOLOGY

3.22 These results suggest that the POPE methodology may be a robust way of evaluating link transit time benefits, particularly when most of the key links have all been counted and journey times have been undertaken.

3.23 The POPE methodology for accidents should be treated with caution, as it is normal for changes in accidents to be assessed over 3-5 years. Therefore, conclusions can only be considered as indicative when they are derived from only one year’s data.

3.24 Thus, the POPE methodology will continue to be used on other schemes in order to provide a larger sample to verify POPE as an evaluation tool.

4. Economic Benefits of the Two Schemes

INTRODUCTION

4.1 Economic benefits of a scheme have been traditionally assessed using the Government’s COBA (Cost Benefit Analysis) program, which considers changes in:

• Link transit time, which is the time on each affected link both before and after opening weighted by vehicle flows;
• Vehicle operating costs (VOC), reflecting fuel and other operating costs calculated by a change in total distance travelled on the affected links, but also considering vehicle speeds; and
• Accident rates and costs, which change after infrastructure improvements are made as accidents are normally less frequent on new roads.

4.2 This section presents a comparison of predicted benefits as calculated by COBA and an assessment of what those benefits would be if the outturn traffic volumes and journey time savings were known at the time.

COBA RE-EVALUATION

4.3 The original Order Publication Report (OPR) COBA appraisal provided the level of benefits that were predicted for these schemes at Public Inquiry. These COBA assessments have been obtained from Government records, and then three additional assessments have been undertaken to provide a re-evaluation of scheme benefits. These were:

• Replication of the original OPR COBA results, using COBA version 9M 1A;
• Re-assessment of benefits after the introduction of actual traffic volumes, rather than predicted traffic volumes, whereby the outturn traffic volumes are also input into the Do Minimum scenario; and
• A validation of journey time definitions within the COBA to more closely reflect actual journey times.

4.4 Figures 4.1 and 4.2 overleaf show the simple COBA network that was used in the appraisal of these schemes, and Tables 4.1 - 4.4 show the Low and High growth COBA results for each of these stages for each of the two A43 improvement schemes.

Figure 4.1 - COBA network for Silverstone

 

A43 Silverstone Section

4.5 Tables 4.1 and 4.2 show the re-assessment of economic benefits for the A43 Silverstone improvement, where all costs and benefits are shown in 1988 prices discounted to 1988 (at 6%).

Table 4.1 - Present Value of Benefits for Silverstone at Low Growth

Silverstone (£000’S)
LOW GROWTH	0. COBA Replication		1. Updating Economic Parameters
COBA ITEM	OPR (printout)	Replication	Outturn Count data included	Count and Journey Times included
Link Transit Time	12,910	12,915	24,423	22,759
Operating Costs - Fuel	-1,500	-1,500	-2,097	-2,100
Operating Costs - Other	-797	-794	-793	-831
Junction Delay	565	565	1,622	1,382
Accidents Link	9,921	9,921	13,548	13,548
Accidents Junction	775	775	871	871
Construction Delay	0	0	0	0
Main Exp Saving	-295	-295	-295	-295
PVB (£)	21,579	21,587	37,279	35,334

Table 4.2 - Present Value of Benefits for Silverstone at high growth

Silverstone (£000’S)
LOW GROWTH	0. COBA Replication		1. Updating Economic Parameters
COBA ITEM	OPR (printout)	Replication	Outturn Count data included	Count and Journey Times included
Link Transit Time	25,319	25,326	35,288	33,223
Operating Costs - Fuel	-1,079	-1,079	-1,252	-1,258
Operating Costs - Other	-878	-875	-770	-810
Junction Delay	1,464	1,464	1713	1,509
Accidents Link	14,712	14,711	17,500	17,500
Accidents Junction	1,054	1,055	1,315	1,315
Construction Delay	0	0	0	0
Main Exp Saving	-295	-295	-295	-295
PVB (£)	40,297	40,307	53,499	51,184

4.6 Table 4.1 shows that for the A43 Silverstone section, the predicted economic benefits of this scheme at the time of the Public Inquiry were estimated to be £21.6m for a Low Growth assumption and £40.3m for High Growth. We have replicated this assessment, as shown in column 2 of Tables 4.1 and 4.2.

4.7 When the actual traffic volumes are inserted into the assessment, the benefits increase substantially to around £37m for Low Growth (a 70% increase) and £53.5m for High Growth, which represents a 33% increase. This column therefore reflects the COBA run that would have resulted if the COBA had been done at the OPR stage, but the actual 2003 flows were somehow given to the consultant at that time.

4.8 The inclusion of refined journey time calculations to reflect actual journey times observed after opening does not change the benefits significantly, suggesting that the COBA is calculating times adequately in its default settings, and also confirms that the inclusion of outturn traffic volumes into the Do Minimum (DM) scenario do not result in significantly increased delays and that the DM times remain robust.

4.9 Table 4.3 and 4.4 below show the results of the re-evaluation of economic benefits for the A43 Syresham section.

Table 4.3 - Present Value of Benefits for Syresham at low growth

Syresham (£000’S)
LOW GROWTH	0. COBA Replication		1. Updating Economic Parameters
COBA ITEM	OPR (printout)	Replication	Outturn Count data included	Count and Journey Times included
Link Transit Time	4,268	4,268	9,226	9,310
Operating Costs - Fuel	-360	-361	-700	-708
Operating Costs - Other	358	357	573	568
Junction Delay	-176	-176	429	375
Accidents Link	3,994	3,993	6,067	6,068
Accidents Junction	392	392	359	359
Construction Delay	0	0	0	0
Main Exp Saving	-129	-129	-129	-129
PVB (£)	8,347	8,344	15,825	15,843

Table 4.4 - Present Value of Benefits for Syresham at high growth

Syresham (£000’S)
LOW GROWTH	0. COBA Replication		1. Updating Economic Parameters
COBA ITEM	OPR (printout)	Replication	Outturn Count data included	Count and Journey Times included
Link Transit Time	8,003	8,003	14,420	14,598
Operating Costs - Fuel	-283	-284	-442	-448
Operating Costs - Other	426	424	628	622
Junction Delay	-210	-209	600	517
Accidents Link	6,210	6,210	8,437	8,437
Accidents Junction	585	585	551	551
Construction Delay	0	0	0	0
Main Exp Saving	-129	-129	-129	-129
PVB (£)	14,602	14,600	24,065	24,148

4.10 Table 4.3 and 4.4 show that for the A43 Syresham section, the predicted economic benefits of this scheme were estimated to be £8.3m and £14.6m for Low and High Growth respectively. These original predictions have been replicated.

4.11 When the actual traffic volumes are used, the benefits increase substantially to around £16m for Low Growth (a 90% increase) and £24m for High Growth, which represents a 65% increase.

4.12 The inclusion of actual journey times observed after opening also do not change the benefits significantly.

4.13 Clearly however, Tables 4.1 - 4.4 show that the inclusion of actual traffic volumes and journey times significantly increases the level of economic benefits accruing for these related improvements. The most important factor in this increase is the level of traffic growth in the corridor, which has been larger than predicted, thus the expected time savings are accruing to a greater level of traffic volumes.

4.14 For example, the predicted traffic volumes on the A43 Bypass at Silverstone and Syresham in 2003 were 21,200 and 19,700 vpd respectively, whereas the actual traffic volumes at these locations were 33,900 and 34,800 vpd respectively. This is a 60% increase at Silverstone and 77% increase at Syresham.

4.15 Table 4.5 below shows the weighted COBA and Outturn results, obtained from 60% of the Low Growth result and 40% of the High Growth Result. This shows that the outturn Silverstone benefits are 43% higher than predicted and for the Syresham section, the benefits are 77% higher than predicted.

Table 4.5 - Comparison of Weighted Economic Benefits

	Predicted Benefits £m	Outturn Benefits £m	% Increase £m
Silverstone Section	29.1	41.7	43%
Syresham Section	10.8	19.2	77%

4.16 The previous section showed that additional traffic volumes have been attracted into the A43 corridor from other routes, notably the M40, A361 and A422. The COBA networks used for the assessment of benefits did not include these other routes and therefore the predictions were based on a straight switch of traffic from the old road to the new road. This approach clearly underestimated the level of benefits predicted for these schemes. Two alternatives could have been modelled, namely

• a larger COBA network that included all links likely to experience a change in traffic volume and time; or
• a Variable Trip Matrix (VTM) approach which could take some account of "induced" traffic, however, with an observed 30% increase in traffic, a VTM approach would not have included such an increase in Do Something flows.

Accidents along the Improvement Scheme

4.17 Tables 4.1 – 4.4 show that the total predicted accident benefit of both of the A43 Improvement schemes was estimated to be £15.082m for low growth and £22.561m for high growth. The accident benefits for the two sections have been summed to give an overall benefit, using 60% of low growth and 40% of high growth.

4.18 The inclusion of outturn traffic volumes significantly increases the level of accident benefits, as with the case with the link transit benefits. Again, for both schemes in total, accident benefits of £20.846m for low growth and £27.803m for high growth are shown.

Table 4.6 - Weighted Economic Benefits for Accidents along the Improvement Scheme

	Predicted Benefits £m	Outturn Benefits £m	% Increase £m
Improvement Scheme	18.1	23.6	30%

4.19 Table 4.6 above shows that the weighted outturn benefits are 30% higher than that predicted.

COMPARISON OF POPE AND COBA METHODOLOGY

4.20 The previous section showed that actual savings in vehicles hours could be used a proxy for the change in link transit and accident benefits, whereas this section has undertaken a good deal of COBA manipulation to insert actual traffic volumes and times into the original OPR COBA, to evaluate the level of benefits that would accrue given the COBA methodology, but using actual flows and times.

4.21 Tables 4.7 and 4.8 show the comparison, for link transit benefits, between the POPE and COBA methodologies for the Silverstone and Syresham schemes respectively. Table 4.9 overleaf shows the same comparison for the accident benefits.

Table 4.7 - Comparison of POPE and COBA Methodologies for Link Transit Benefits - Silverstone

	Predicted Link Transit Benefits £m	Outturn Link Transit Benefits £m	% Increase £m
POPE Methodology	17.9	29.6	65%
COBA Methodology	17.9	26.9	51%

Table 4.8 - Comparison of POPE and COBA Methodologies for Link Transit Benefits – Syresham

	Predicted Link Transit Benefits £m	Outturn Link Transit Benefits £m	% Increase £m
POPE Methodology	5.8	10.9	85%
COBA Methodology	5.8	11.4	98%

Table 4.9 - Comparison of POPE and COBA Methodologies for the Accidents – Improvement Scheme

	OPR Predicted Benefits £m	Outturn Accident Benefits £m	% Increase £m
POPE Methodology	18.1	10.2	-44%
COBA Methodology	18.1	23.6	31%

4.22 This comparison shows that the POPE and COBA methodologies produce similar levels of outturn benefits for the link transit benefits, and thus POPE is potentially a robust way of establishing outturn economic benefits without recourse to timeconsuming COBA manipulations. This is not the case when evaluating accident benefits. Clearly, the two methodologies show very different results, but this confirms the need for at least 3 years worth of accident data, post scheme opening, and not one years worth, as was used here.

RE-EVALUATION OF SCHEME COSTS

4.23 As well as re-assessing the level of benefits accrued by the two A43 schemes, we have also undertaken a review of predicted and actual costs. Tables 4.10 and 4.11 overleaf present the predicted costs calculated before opening as part of the justification of the scheme for both the Silverstone and Syresham improvements, as well as the actual costs converted to the same price base so that direct comparisons can be made between them.

Table 4.10 - Scheme Costs in 1988 Prices and Values

	Silverstone		Syresham
	predicted £m	outturn £m	predicted £m	outturn £m
Construction	7.936	5.756	4.058	4.317
Land	0.250	0.233	0.206	0.233
Preparation	0.491	0.204	0.256	0.154
Supervision	0.246	0.509	0.128	0.385
Total	8.923	6.702	4.648	5.089

Table 4.11 - Scheme Costs in 2002 Prices and Values

	Silverstone		Syresham
	predicted £m	outturn £m	predicted £m	outturn £m
Construction	30.685	22.256	15.691	16.692
Land	0.967	0.901	0.797	0.901
Preparation	1.899	0.788	0.990	0.595
Supervision	0.951	1.969	0.495	1.488
Total	34.502	25.914	17.972	19.677

4.24 The comparison of OPR and Outturn costs show:

• For the Silverstone section, costs were estimated to be £8.9m (at 1988 prices and values), whereas the actual costs converted to the same price base suggested £6.7m, showing the outturn is 25% below predicted;
• For the Syresham section, the predicted and actual costs were very similar; and . Converting the predicted costs into 2002 prices and values results in a prediction of £34.5m for the Silverstone section against outturn costs of £25.9m, and prediction of £18m for the Syresham section against outturn costs of £19.7m.

4.25 Outturn costs shown are exclusive of two unique events, namely:

• The extra costs that accrued due to the outbreak of Foot and Mouth disease during the construction period. These additional costs were due to change in earthworks, drainage and pavements, and have been estimated at £17.6m; and
• The acceleration of completion to be ready for the F1 weekend added another £8m to the overall cost.

4.26 Together, these additional costs amounted to £25.6 million, but have been excluded from the above assessment, as clearly, these could not have been foresaw in the predictions of construction costs for these schemes.

5. Evaluation Summary Table

INTRODUCTION

5.1 In order to evaluate fully the effects of the opening of the two A43 improvement schemes, we have undertaken a review of the Appraisal Summary Table (AST) prepared for each of the improvements. Tables 5.1 and 5.2 present the AST’s for Silverstone and Syresham bypasses respectively.

5.2 These AST’s summarise the predicted impacts of the two schemes across a range of different sub-objectives. The sub-objectives considered within an AST are:

• Environmental impacts such as Noise, Local Air Quality, Landscape, Biodiversity, Heritage and Water;
• Safety impacts, measuring reduction in accidents;
• Economy impacts including savings in Journey time and Vehicle Operating Costs, Scheme Cost and Reliability of journeys;
• Accessibility impacts, such as change in access to public transport, severance within communities and impact on pedestrian and other modes; and
• Integration, measured by how the scheme accords with local policy.

APPRAISAL SUMMARY TABLES (AST)

5.3 The main points to note from the Silverstone and Syresham ASTs are:

Environment:

• Improvement due to vehicles re-routed away from village so that 52 properties would benefit from reduced noise in Silverstone and 18 from Syresham;
• Similarly, 85 properties would see an improvement in air quality in Silverstone and 77 in Syresham;
• Negative impacts forecast on landscape, biodiversity and Water for both schemes;
• Improvements to heritage as 20 listed buildings would benefit in Silverstone village and one in Syresham;

Safety

• Significant number of accidents saved, (715 accidents in Silverstone and 313 in Syresham over 30 years);

Economy

• The original AST showed 17% of all vehicles were HGV’s. New figures from 2002 suggest 25% are HGV’s, and this proportion of HGV’s has been maintained after opening;
• Significant benefits from journey time savings in both Silverstone and Syresham sections; and
• Moderate benefits in terms of improvements to journey reliability.

• Download tables 5.1 and 5.2 (70KB PDF)

Accessibility

• Large benefits to severance and ‘pedestrian modes’ forecast by statement of removal of 86% of traffic from Silverstone and slight benefits from Syresham even though nearly all of the traffic is forecast to be removed from the village.

Integration

• Positive benefit shown for Silverstone and Syresham as scheme assists development in Brackley as well as assisting development of Silverstone Motor Race Circuit.

OUTTURN EFFECTS

5.4 In order to assess the actual or outturn effects of the opening of the two improvement schemes, we have produced an Evaluation Summary Table (EST), which mirrors the appearance of the AST, and includes details of the actual sub-objectives that have been evaluated.

5.5 The POPE process concentrates on economy and safety impacts of new schemes at present, but this may be widened to include environmental effects, and guidance is currently being written to outline the best approach for these objectives at present.

5.6 The main points to note on the EST are:

Environment

5.7 The environmental aspects of the two A43 schemes have not been evaluated in detail. The main premise for the benefits identified in the AST is that properties along the old A43 will experience a benefit in noise and air quality due to the removal of traffic onto the bypasses, and as the traffic reductions in the two villages have been greater than predicted, it is fair to say that the environmental impacts reported in the AST are likely to have been achieved.

5.8 In terms of negative forecasts such as landscape, Biodiversity and water, no assessment of these sub-objectives have been carried out at present.

Safety

5.9 The AST for both the Silverstone and Syresham improvement schemes predicted significant accident savings. In order to evaluate whether these predicted savings are likely we have undertaken an initial evaluation of accident savings accrued for the new schemes.

5.10 Normally, it is usual for accident savings to be evaluated at least three years after opening in order to get a fair reflection in the number of accidents in the corridor, therefore this evaluation for the One Year After Evaluation is an initial view and cannot be considered as a firm conclusion at this time.

5.11 Despite this caveat, we have obtained accident data for 3 years from 2001, i.e. two years prior to scheme opening and a year post scheme opening. Table 5.3 below summarises the accident rates along the A43 from Brackley to Towcester. The Average flows have been taken from a site on the A43 at Brackley.

Table 5.3 – Summary of Accident Data

Year	Length of road (KM)	Average Flow (AADT)	No. of accidents	Accident Rate (PIA / MVKM)
2001	16.1	21862	44	0.342
2002 (before opening)	16.1	22944	48	0.356
2003	16.1	29267	28	0.163

5.12 The accident rate has dropped from 0.35 personal injury accidents (PIA) per million vehicle kilometres (mvkm) to 0.163 PIA/mvkm. The national average accident rate for a dual carriageway is 0.165 PIA/mvkm, which shows that the improvement schemes has reduced the accident rate to those typical for a road of this type. If higher flows are used for the assessment (for example the AADT at Silverstone is around 32,000), then the observed accident rate has dropped below the national average.

5.13 We do stress again however, that this is a One Year Evaluation, and firm conclusions should really not be derived until at least three years after opening, but the initial signs are that the scheme has been successful in reducing accidents on the A43.

5.14 Atkins have obtained the locations of the observed accidents, and Figures 5.1 and 5.2 show the location of these accidents in 2001 and 2003 respectively.

Figure 5.1 – Accidents along the A43 between Brackley & the A5 at Towcester, in 2001

Figure 5.2 - Accidents along the A43 between Brackley & the A5 at Towcester, in 2003

5.15 These figures clearly show the reduction in the number of accidents on this section of A43. The number of accidents has been reduced from 44 in 2001, to 28 in 2003, a 36% reduction. Figure 5.2 also clearly shows that there are very few accidents on the A43 around the villages of Syresham and Silverstone.

5.16 Within the AST, the predicted accidents savings of the 30 year assessment period have been reported, and in order to provide an initial view on the robustness of these conclusions, we have predicted the number of accidents over the 30 year assessment period.

5.17 In order to do this, we have assumed a conservative 1% growth in traffic each year, and a consistent accident rate of 0.16, also assuming a 30,000 AADT average in 2003, this results in a total of 1686 accidents without the bypass and 984 accidents with the bypass, a saving of 702 accidents over the section, which includes both the Silverstone and Syresham bypasses.

5.18 The proportion of fatal/serious/slight accidents has been determined from figures quoted in COBA 11, i.e. 0.025 fatal, 0.148 serious and 0.827 slight. From COBA 11 we also have the average severity split (that is, the number of fatal, serious and slight casualties per accident). The final accident and casualty figures are shown in the EST.

5.19 This compares well with the prediction of accident savings reported in the two AST’s.

Economy Impacts

5.20 As outlined in the previous section, Economy impacts are measured by changes in journey times and our new information suggests that these changes are around 6-10 minutes, and when applied to higher traffic growth than originally forecast, then the actual economic benefits are higher than those predicted. For the Silverstone section, the benefits are 50% higher and 77% higher for the Syresham section.

Accessibility Impacts

5.21 The Silverstone AST predicted that accessibility benefits would accrue in terms of reduced severance and improved conditions for pedestrians and other modes, and these would result in an 86% reduction in traffic in the town.

5.22 Outturn traffic volumes suggest that 90% of the Silverstone through traffic and 98% of traffic in Syresham has been removed, again suggesting that the accessibility benefits outlined in the AST are fair.

Integration

5.23 The AST again states that the scheme facilitates additional development in Brackley as well as further improvements to the Silverstone Motor Race Circuit.

5.24 In terms of Planning Policy within the County and the developments in Brackley, the County has advised that only limited development is currently planned in Brackley, but this will be considered further in the Five-Year After assessment for these schemes.

5.25 Also, the operation of accessing and egressing to/from the F1 weekend was generally reported as being an improvement over preceding years, providing confidence in the continued use of Silverstone as a regular F1 venue.

Summary

5.26 A summary of effects across all evaluation sub-objectives are included in the EST’s for Silverstone and Syresham in Tables 5.4 and 5.5 respectively.

• Download tables 5.4 and 5.5 (65KB PDF)

6. Summary of Conclusions

6.1 The Highways Agency has a requirement to carry out re-evaluations of trunk road schemes recently implemented by the Department of Transport. The purpose of these re-evaluations is to provide a back check of the levels of benefit accruing from new schemes and to determine how far the department achieves the objectives and benefits it claims from its road programme.

6.2 In summary, the main points to note from the One Year Evaluation of the A43 Silverstone and Whitfield Turn – Brackley Hatch (Syresham) improvements are:

• Before the improvements scheme the old A43 route through the villages of Silverstone and Syresham carried around 27,000 . 28,000 vehicles per day (on an average weekday);
• The A43 (T) Silverstone and Syresham Bypass, which officially opened on 18th September 2002, carried around 28,000 . 30,000 vehicles per day, a month after opening;
• A year later, the traffic volumes on the two sections have grown to 34,000 on the Silverstone section and 35,000 vpd on the Syresham Section, which represents a 30% increase in traffic from 2002 to 2003;
• 90% of traffic has been removed from the bypassed section of old A43 in Silverstone, and 96% has been removed in Syresham, suggesting that the schemes have been successful in removing through traffic from these villages;
• The traffic volumes are shown to reduce on other roads in the corridor, particularly the M40, north of Junction 10, A361 and A422, which explain these significant increases on the A43;
• Journey time information suggests that time savings of up to 10 minutes are being forecast for journeys along the A43 following the two improvement schemes;
• For the A43 Silverstone improvements, the predicted economic benefits (weighted) were £29m, whereas with actual traffic volume and journey time information, the outturn benefits have been re-calculated to be £41m, an increase of 43% over those predicted;
• The new POPE methodology confirms that actual benefits are substantially higher than those forecast, based on percentage change in vehicle hours against those predicted in the original COBA assessments;
• For the Syresham section, the predicted economic benefits (weighted) were £11m, whereas the outturn benefits have been re-calculated to be £19m, an increase of 75% over those predicted;
• Again, the new POPE methodology confirms these economic benefit increases for the Syresham section, again based on percentage change in vehicle hours against those predicted;
• The POPE methodology suggests that it may be a good method of evaluating the level of time benefits, but not accident benefits in the first year after opening, however, these conclusions must be validated from more schemes;
• These increases in benefits are largely due to more traffic being observed on the A43 compared to predictions. The journey time savings per vehicle are similar between observed and predicted, and therefore the increased traffic volumes lead to increased benefits;
• Clearly, the completion of the A43 has led to a reassignment of traffic onto the road, and this additional traffic was not considered as part of the original economic assessment. With this level of new traffic, a Variable Trip Matrix (VTM) approach could have been applied, which would have increased the predicted level of benefits. The approach adopted led to a conservative estimate of economic benefits for these schemes;
• The predicted scheme costs for the A43 Silverstone and Syresham schemes were estimated to be £8.91m and £4.65m respectively at 1988 prices compared to an actual spend of £6.65m and £4.94m for the two schemes, showing that the actual spend at Syresham was close to that predicted, and actual spend was less than predicted at Silverstone;
• The A43 improvements have led to a reduction in the number of accidents in the corridor, where up to 20 injury accidents have been saved in the first year after opening. The 2003 accident records do show that there is still a cluster of accidents on the A43 South of Towcester which should be investigated at a later date, when more accident data is available, as more traffic on this section may lead to more accidents;
• Evaluation Summary Tables have been prepared for these two sections of A43 improvements and can be directly compared with the AST"s prepared before opening. These show that the prediction of the relief of traffic in Silverstone and Syresham was accurate, and that the accident savings predicted was again robust.

6.3 Evaluation of other sub-objectives within the AST will be carried out as part of the Five-Year After assessment, which will consider accident reductions in more detail, as well as how land use has changed in the area as a result of the A43 Silverstone and Whitfield Turn to Brackley Hatch improvement schemes.