Further reflections

Overview

Research undertaken to inform this review identified related areas that could be affected by the options presented. These are discussed in this section of the report.

Kinetic energy in collisions

International evidence is strong on the link between relative vehicles speeds and outcomes when collisions occur. The Nilsson power law (see Health, Safety and Wellbeing – Accidents (All severity) Section for further details) demonstrates a relationship between recorded vehicles speeds and road safety outcomes. These are:

  • Increasing vehicles speeds leads to greater numbers of road safety collisions with increased levels of severity; and
  • Decreasing vehicles speeds leads to reduced numbers of road safety collisions with reduced levels of severity.

The amount of kinetic energy in a collision increases with vehicle speed and mass. Kinetic energy is dissipated when a collision occurs and is visibility demonstrated in the damage to vehicles and infrastructure and in injuries to road users. 

Due to the mass of batteries in electric vehicles, they tend to weight significantly more than conventional petrol/diesel vehicles. Reducing National Speed Limits potentially offsets the road safety impacts of increasing vehicles mass. Similarly, HGVs are larger and weigh significantly more than other vehicles which may lead to more kinetic energy. However, the evidence from England and Wales does not show a significant increase in HGV traffic speeds and collisions which may be reflected on the Scotland Road Network.

Vehicle Standards

The Scottish Government is committed to phasing out the need for new petrol and diesel cars and vans by 2030. This aims to reduce Scotland’s carbon footprint by facilitating the move to electric vehicles. This creates two significant road safety concerns.

  • The mass of electric vehicles is significantly greater than conventional vehicles, so when a collision occurs more kinetic energy requires to be dissipated; and
  • As the vehicles are quieter than conventional vehicles, they are less likely to be heard/noticed by other road users.

Since leaving the EU on the 31st December 2020, Great Britain has not been required to follow the rules of the EU single market, including the adoption of technical standards. From the 6th July 2022 the EU under the General Safety Regulation, introduced new requirements for safety features to be included in all new road vehicles. The features now required to be included in all new vehicles within the EU are identified within Table 8-1.

Table 8-1 – New Safety Vehicle Requirements in the EU
For All road Vehicles For Cars and Vans For Buses and Trucks
  • Intelligent speed assistance
  • Reversing detection with camera or sensors
  • Attention warning in case of driver drowsiness
  • Emergency stop signal
  • Cybersecurity measures
  • Lane keeping assistance
  • Advanced emergency braking
  • Event data recorders
  • Detection and warnings to prevent collisions within pedestrians or cyclists
  • Tyre pressure monitoring systems

It is considered that some of these new features potentially will have an impact upon driver behaviour with respect to the speed at which vehicles travel, in particular intelligent speed assistance. Great Britain could introduce more stringent vehicle standards however, it would be difficult to be certain on the impacts.

As the renewal of the national fleet will take a considerable period of time, it is unclear when the divergence in safety standards between the EU and Great Britain will impact upon road safety performance in Scotland.

20mph Speed Limit in Wales

Wales introduced the default 20mph legislation in September 2023 on restricted roads only in residential and built-up areas. Since the introduction, there has been a 20% drop in insurance claim for car collisions. The reduction in insurance claims in Wales suggests that there may be a reduction in road safety collisions including damage only collisions which are not recorded in STATS19.

It stands to reason that the implementation of the options presented may have a similar economic impact in reducing damage only insurance claims that is not accounted for in the economic appraisal undertaken.

Speed Limit Review in Ireland

Published on the 14th of September 2023, the Speed Limit Review in Ireland fulfils a Programme for Government commitment in Ireland that included their Road Safety Strategy 2021 – 2030. An overview of the approach taken in this work is presented within Appendix L of this report.

The Irish review had a number of recommendations including for National Secondary Roads, which are broadly equivalent to single carriageway A roads in Scotland to reduce speed limits from 100 km/h (62mph) to 80km/h (50mph). The conclusions from the Irish Work showed that they followed an approach broadly in line with international evidence and that of the approach taken to assess the options for the Scottish Road Network presented in this report.

Driver Education & Enforcement

Road Safety Scotland is part of the Scottish Government and aims to promote awareness of road safety issues in Scotland through educational materials and publicity campaigns (Educational materials and publicity campaigns are shared on the Road Safety Scotland website). The campaigns rolled out by Road Safety Scotland cover a wide range of driver behaviours including speed. These campaigns often involve a number of different mediums.

Evaluation of road safety campaigns typically involves target surveys to understand their impacts on driver attitudes. These impacts are not directly relatable to reported collision data in collisions.

It stands to reason if drivers are unaware of changes in speed limits that the road safety benefits of the options would not be obtained. Accordingly, it is considered imperative that road safety campaigns would require to support the implementation of the options presented in this report.

Police Scotland and the safety camera programme undertake ongoing enforcement of speed limits within Scotland. Their ongoing work helps support educational programmes and to ensure compliance with speed limits.

Heavy Goods Vehicles (HGV) Speed Limits

On 6th April 2015, the National Speed Limit for HGVs in England and Wales for more than 7.5 tonnes maximum laden weight (HGVs >7.5t) was increased from 50mph to 60mph on dual carriageways and from 40mph to 50mph on single carriageways. Scottish Ministers did not mirror these increases which has led to a discrepancy in speed limits for goods vehicles (<7.5t at the border between Scotland and England. As can be seen in Table 2-4, the current speed limit for HGVs >7.5t in Scotland is 40mph on single carriageways and 50mph on dual carriageways.

Following implementation of the changes to the National Speed Limit for HGVs in England and Wales, the impacts of the speed limit changes were monitored, and the findings reported. These include:

  • No evidence of a change in collisions involving HGVs on all study roads, single carriageway roads or dual carriageway roads;
  • On single carriageways the average speed of HGVs increased by 1.6 mph (from 44.1 to 45.7 mph);
  • On single carriageways the average speed of light vehicles increased by 0.3 mph (from 47.9 to 48.2 mph);
  • On dual carriageways, the average speed of HGVs increased by 0.5 mph (from 52.0 to 52.5 mph);
  • On dual carriageway, the average speed of light vehicles increased by 0.1 mph (from 65.0 to 65.1 mph);
  • No statistically significant effect on air quality, nor perceptible change in noise level was recorded over a typical 18-hour day or during individual hours at night; and
  • Economic benefits have principally comprised of business user time savings and business user vehicle operating costs.

The evaluation of changes made to the National Speed Limit of goods vehicles (>7.5t) in England and Wales in April 2015, has concluded that the actual speeds of goods vehicles (>7.5t) has not significantly changed. Harmonised with this conclusion is that the wider impacts of the changes were considered to not be statistically significant.

Recognising these findings, it is proposed to amend the options appraised in this report to incorporate the changes made in England with respect to goods vehicles (>7.5t). This would:

  • simplify speed limits for goods vehicles (>7.5t) between the two jurisdictions (Scotland and England);
  • help reduce the speed differentials in Scotland;
  • reduce driver frustration; and
  • improve journey time reliability.

The resulting options are as follows:

Option 1

  • On single carriageways:
    • Cars and motorcycles would have a decreased speed limit of 50mph; and
    • Goods vehicles (>7.5t) would have an increased speed limit of 50mph.
  • On dual carriageways as follows:
    • Goods vehicles (>7.5t) would have an increased speed limit of 60mph.
  • On motorways:
    • No alterations to speed limits proposed.

Option 2

  • On single carriageways:
    • Cars and motorcycles would have a decreased speed limit of 50mph; and
    • Goods vehicles (>7.5t) would have an increased speed limit of 50mph.
  • On dual carriageways as follows:
    • Cars and motorcycles would have a decreased speed limit of 60mph; and
    • Goods vehicles (>7.5t) would have an increased speed limit of 60mph.
  • On motorways:
    • All vehicles limited to 60mph.

In considering appraisal of the likely impacts of each option, it is unlikely that changes to the options would affect the appraisals presented in section 7 of this report.