Option appraisal summary
Overview
This section of the report presents a comparative summary of the findings from the appraisal in Section 6 of the options and future scenarios. For comparison purposes, the options have been assessed against the TPOs in Table 7-1 and Table 7-2.
| Identified Road Safety Outcomes | 100% Compliance - Option 1 | 100% Compliance - Option 2 | Realistic Compliance - Option 1 | Realistic Compliance - Option 2 |
|---|---|---|---|---|
| Reduce collision rates and severity on single carriageways where speed has been identified as a contributory factor. | Major Benefit | Major Benefit | Major Benefit | Major Benefit |
| Reduce collision rates and severity on dual carriageways where speed has been identified as a contributory factor. | No impact or benefit | Moderate benefit | No impact or benefit | Moderate benefit |
| Reduce speed differentials between HGVs and other traffic. | Moderate benefit | Moderate benefit | Minor benefit | Minor benefit |
| Identified Road Safety Outcomes | 100% Compliance - Option 1 | 100% Compliance - Option 2 | Realistic Compliance - Option 1 | Realistic Compliance - Option 2 |
|---|---|---|---|---|
| Reduce collision rates and severity on single carriageways where speed has been identified as a contributory factor. | Major Benefit | Major Benefit | Major Benefit | Major Benefit |
| Reduce collision rates and severity on dual carriageways where speed has been identified as a contributory factor. | No impact or benefit | Moderate benefit | No impact or benefit | Moderate benefit |
| Reduce speed differentials between HGVs and other traffic. | Moderate benefit | Moderate benefit | Minor benefit | Minor benefit |
In Table 7-3 and Table 7-4, the options have been compared against the Transportation Planning Objectives identified in section 3 of this report. From this comparison it is clear that Option 2 would contribute to all the objectives whilst Option 1 would contribute to all road objectives except reducing collision rates on dual carriageways. Option 2 is unlikely to obtain the full benefits as dual carriageways and motorways are the significantly safer than single carriageways.
An overview of the Options Appraisal is shown in Table 7-3 for Option 1 and Option 2 without policy and for Option 1 and Option 2 with policy.
| Category appraised | 100% Compliance - Option 1 | 100% Compliance - Option 2 | Realistic Compliance - Option 1 | Realistic Compliance - Option 2 |
|---|---|---|---|---|
| Environment - noise and vibration | Minor benefit | Minor benefit | No impact or benefit | No impact or benefit |
| Environment - local air quality (airborne particulate matter) | No impact or benefit | No impact or benefit | No impact or benefit | No impact or benefit |
| Environment - local air quality (Nitrous Oxide emissions) | No impact or benefit | Moderate benefit | No impact or benefit | Minor benefit |
| Climate Change - Greenhouse Gas Emission | No impact or benefit | Minor benefit | No impact or benefit | Minor impact |
| Health, Safety and Wellbeing - accidents (All severity) | Moderate benefit | Major benefit | Moderate benefit | Major benefit |
| Economy - Economic efficiency of the transport system | Major negative impact | Moderate negative impact | Moderate negative impact | Moderate negative impact |
| Comparative Access by Geographic Location | No impact or benefit | Moderate negative impact | No impact or benefit | Minor negative impact |
| Category appraised | 100% Compliance - Option 1 | 100% Compliance - Option 2 | Realistic Compliance - Option 1 | Realistic Compliance - Option 2 |
|---|---|---|---|---|
| Environment - noise and vibration | Minor benefit | Minor benefit | No impact or benefit | No impact or benefit |
| Environment - local air quality (airborne particulate matter) | No impact or benefit | No impact or benefit | No impact or benefit | No impact or benefit |
| Environment - local air quality (Nitrous Oxide emissions) | No impact or benefit | Moderate benefit | No impact or benefit | Minor benefit |
| Climate Change - Greenhouse Gas Emission | No impact or benefit | Minor benefit | No impact or benefit | Minor benefit |
| Health, Safety and Wellbeing - accidents (All severity) | Moderate benefit | Major benefit | Moderate benefit | Major benefit |
| Economy - Economic efficiency of the transport system | Moderate negative impact | Moderate negative impact | Minor negative impact | Moderate negative impact |
| Comparative Access by Geographic Location | No impact or benefit | Moderate negative impact | No impact or benefit | Minor negative impact |
A comparison of Option 1 and Option 2 is shown in Table 7-3 and Table 7-4. When considering the Options against the appraisal criteria, the comparative impacts of the options is:
- Both options lead to small reductions in the amount of noise generated by road traffic;
- Option 2 would lead to a moderate reduction in NOx emissions that would not be observed under Option 1. Both options have a non-statistically significant impact on particulate matter;
- Option 2 leads to a minor reduction in greenhouse gas emissions than Option 1;
- Option 2 would achieve a greater reduction in road safety collisions than Option 1; and
- Option 1 would lead to a minor economic benefit compared to Option 2.
The differences in impacts in the appraisal are influenced by the proposed change in HGV speed limits on rural dual carriageways which are proposed under Option 2 but not Option 1. The appraisal of the options demonstrates that if impacts are to be achieved that they are highly sensitive to the level of speed limit compliance.
The initial BCRs of the options range from 5.6 to -180.5, depending on the future scenarios and implementation approach assumed. This implies the proposal could achieve value for money ranging from Very High to Very Poor on the basis of initial BCR impacts. The highest levels of value for money are achieved by Option 1 in particular when considering the realistic compliance future scenarios.
The appraisal work undertaken has considered the impacts of the options for several years into the future. Outcomes of the appraisal further into the future are more uncertain due to events and policies which cannot be accurately predicted.
Environment – Noise and Vibration
The appraisal of noise had identified that noise levels would be expected to fall most under Option 1, although the impacts would be significantly linked to the level of compliance achieved. The impacts of “with policy” and “without policy” future scenarios would be relatively minimal.
An assessment of the impacts of the options and future scenarios with respect vibration effects has not been undertaken as it is considered that such impacts would be imperceptible.
A theoretical 100% compliance in the change in speeds would result in noise level changes between no benefit or impact to minor beneficial impact.
Environment – local air quality (airborne matter and Nitrogen Oxide emissions)
Option 2 is likely to lead to a minor improvement in air quality with respect to NOx emissions with realistic compliance. The improvements are likely to increase to moderate improvement in NOx emissions if full compliance with speed limits is obtained. Option 2 is likely to have a negligible impact on particulate matter with realistic compliance. Option 2 with full compliance will have a negligible effect on PM2.5 but a minor negative impact on PM10 in all futures except with policy in 2025 where a negligible impact is anticipated.
Under Option 1, the various futures considered do not suggest any change in NOx, PM10 and PM2.5 emissions.
Climate Change – Greenhouse Gas Emissions
The emissions reductions in Option 2 both with and without policy are slightly greater than Option 1. A key factor contributing to the reduction was the increased speed of HGVs, as their emission efficiency improves at higher speeds as the HGVs will generate lower carbon emissions.
The assessment of the options demonstrates a significant difference in emission reduction between the 100% compliance and the realistic compliance futures. Emissions reductions being significantly greater for 100% compliance when compared to the realistic compliance futures.
When applying the DMRB LA111 scale to the 100% compliance scenario, the benefits ranged from minor for Option 2 with policy to moderate without policy. In contrast, the realistic scenario only showed negligible benefits.
Health, Safety and Wellbeing – Accidents (All severity)
All options presented are envisaged to lead to a significant reduction in recorded serious and fatal severity road collisions. These impacts are generally increased in Option 2 over Option 1 due to Option 2 impacting upon additional roads.
The increase of National Speed Limits for HGVs aims to reduce the speed differentials between vehicles and may lead to a reduction in driver frustration, reckless manoeuvres and reported collision data.
Obtaining greater levels of compliance with the proposed speed limits potentially leads to a significant increase in the lives that can be saved. The “with policy” and “without policy” future scenarios have a non-statistically significant impact on the collisions saved.
Economy – Economic efficiency of the transport system
Overall, the scheme is expected to have a negative impact on economic efficiency with the magnitude varying significantly depending on the option taken forward and the future that is achieved.
Within Option 1 the economic efficiency disbenefits may be offset by the benefits to collisions under the realistic compliance scenarios (and nearly offset under 100% compliance). However, this is not the case for Option 2, where the economic efficiency disbenefits significantly outweigh the collision benefits.
The amendments being proposed to HGV traffic under the realistic future scenarios is likely to be relatively minor as the options proposed legitimise current HGV behaviour with respect to speed. This would mirror the experience in England where HGV speed limits were altered in 2015.
Comparative Access by Geographic Location
The impacts of the options and future scenarios with respect to the fisheries routes for Option 1, it is unlikely the long HGV routes will be significantly impacted. This reflects that HGV traffic requires to interact with other traffic that will have its speed limits reduced under the options presented.
Under Option 2, journey times for long HGV routes will be more significantly impacted than Option 1. A high level of compliance may lead to journey times on some long distance routes being increased by up to 30 minutes.