Option generation and sifting

Further to the publication of the 2030 Framework in February 2021, WSP undertook a review which led to the development of a National Speed Management Plan (NSMP) during Summer 2022.

The NSMP preparation process initially involved an extensive research phase to identify speed management initiatives that could form part of a NSMP for Scotland. This involved literature reviews and engagement with international peers and road safety partners across Scotland. Through these activities, a number of speed management initiatives were identified that linked to a number of key themes:

  • Speed Limits on roads subject to the National Speed Limit;
  • Speed Limits on Urban Roads;
  • Speed Management through Roadworks;
  • Event Driven Speed Limits;
  • Speed Management for Environmental Improvements;
  • Use of Technology for Speed Limit Enforcement;
  • Penalties for Speed Violations; and
  • Educational Programmes.

Sifting

An initial sifting process considered speed management initiatives to determine if they would be appropriate for the Scottish road network and support the 2030 Framework. This process assessed initiatives against compatibility with the Safe System approach and having a proven speed management benefit. Initiatives which did not meet both these objectives were discounted from further consideration.

The residual initiatives were then considered in a more detailed assessment, which considered the 2030 Framework challenges, road safety impacts, and Scottish Transport Appraisal Guidance (STAG) criteria. The most credible initiatives from this assessment were presented in the recommendations of the NSMP.

NSMP Recommendations

The conclusions of the NSMP identified several recommendations that could support Scotland’s journey to Vision Zero. These were grouped as:

  • Primary Recommendations – proposed to promote initiatives that lower vehicle speeds and improve compliance with these lowered speed limits. These recommendations were considered to potentially have a significant short-term impact;
  • Secondary Recommendation – Similar to the primary recommendation, however, these initiatives would likely require a longer time to deliver results than the primary recommendations;
  • Research recommendations – where the evidence reviewed was considered inconclusive, these recommendations proposed that further research be undertaken; and
  • Monitoring recommendations – These recommendations identified existing research/trials that were ongoing and proposed that the outcomes of these be monitored.

NSMP Speed Limit Initiatives

An overview of the NSMP speed limit related initiatives is presented below:

i1a - Reduced National Speed Limit on single carriageway roads to 50mph:

Scotland's current National Speed Limit on single carriageway roads is 60mph. This initiative proposes to lower the speed limit to 50mph for cars. Other countries such as Ireland, Sweden and France operate an 80km/h (50mph) speed limit on their rural single carriageways.

i1b - Reduced National Speed Limit on dual carriageways roads to 60mph:

Scotland's current National Speed Limit on dual carriageway roads is 70mph. This initiative proposes to lower the speed limit to 60mph.

i5a - Reduced speed limits during wet weather (variable speed limits) on Single Carriageways, Dual Carriageways and Motorways:

Wet weather can provide more dangerous driving conditions (obscuring vehicle driver vision, increasing stopping distances, etc) which can increase collision risk. Enforceable variable speed limits could be introduced via technology on specific routes in adverse wet weather in order to mitigate against these additional safety risks.

i5d - Reduced Speed Limits during winter month on Single Carriageways, Dual Carriageways and Motorways:

Adverse winter weather conditions, such as high winds, heavy rain and snow are more likely to occur during winter. This initiative is closely linked to initiative i5a. In this case, lower speed limits would be enforced during winter months only in order to mitigate against these additional safety risks.

i5n - Reduced speeds during high winds:

Similar to initiatives i5a and i5d, adverse weather conditions such as high winds may create dangerous driving conditions at higher speeds. This initiative proposes the use of variable speed limits on roads which are known to be affected by high winds (carriageways in rural environments and motorways). The speed limits would be displayed on variable message signs and could be enforced with average speed cameras in order to mitigate against the safety risk.

i5j - Implementation of localised speed limits to reduce collision rates/severity:

This initiative promotes the use of current road safety statistics to determine areas which would benefit from a localised speed limit. The reduction in speed limits aims to minimise speed differentials to make driver decisions easier with a goal of achieving collision and casualty reductions.

i5l - Introduction of localised speed limits of 40mph (single carriageway) and 50mph (dual carriageway) at at-grade junctions:

This initiative would introduce localised speed limits of 40mph (single carriageway) and 50mph (dual carriageway) at at-grade junctions. The main objective is to lower speeds in order to reduce the risk (and/or severity) of collisions at junctions.

Options for Appraisal

Reflecting on the progress to date against the 2030 Framework targets, the development of the options has considered initiatives i1a and i1b that address National Speed Limits as those with the potential to make the most significant contribution towards the 2030 Framework targets. Those remaining initiatives remain initiatives that could be revisited in the future. The resulting two options generated are presented here.

Option 1

This option aims to improve road safety and reduce speed differential on single carriageways.

  • 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:
    • No alterations to speed limits proposed.
  • On motorways:
    • No alterations to speed limits proposed.

Option 2

This option aims to improve road safety and reduce speed differential on Scotland’s Road network.

  • 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.

The recommendations of STPR2 were considered against the key objectives of STPR2. As the options presented within this report directly relate to these recommendations, Table 4-1 provides and overview of how the options may contribute to the STPR2 key objectives.

Table 4-1 – Option Alignment with STPR2 Key Objectives
STPR2 Objective Option Alignment with STPR2
Takes climate action Vehicle emissions are directly related to vehicle speeds, especially in free flow road environments.
Addresses inequalities and accessibility Options proposed are generally aimed at reducing vehicle speeds in free flow road environments where there are links between vehicle speeds and accessibility in terms of travel time catchments.
Improves health and wellbeing Lower vehicle speeds generally make active travel routes more attractive in lower speed environments. The options presented propose to alter speed limit within higher speed environments where the option impacts would be less perceptible to active travel users.
Supports sustainable economic growth Business costs associated with transport are directly linked to time, which is directly linked to vehicle speeds.
Increases safety and resilience Vehicles speeds are directly linked to collision rates and severity.