Main Roads & 20mph - Learning from Dundee's Errors

Yesterday the Roads and Transportation Department of Dundee presented a report to the city's Development Committee on "potential areas where 20mph speed limits could be implemented in the City of Dundee". Whilst we welcome the broad support for 20mph on residential roads we have real concerns that by emphatically excluding any principal roads the report ignores and misrepresents the current Scottish guidance.

The report references the Transport Scotland Guidance on 20mph Limits, yet both misrepresents that guidance and shows little understanding of either the issues or the legal requirements of the Equality Act 2010.

This blog therefore provides our critique of the report from Transportation Department.

Setting speed limits on main roads

First I am very concerned that the report immediately excludes the city’s principal road network. In looking at setting a city-wide default then when the council set specific exceptions then it is making a de-facto decision  on any roads which it excludes. Such a decision would appear to be outside of the current guidelines on setting speed limits and also any such decision could be illegal if the potential for indirectly discriminating against those with protected characteristics have not been fully considered. The latter cannot be merely “brushed aside” with a statement that “There are no adverse issues”. Any consideration of inequality must be founded on a robust and documented analysis. This means that any negative aspects must be fully considered. If this has not been done in developing this policy then it is possible that the decision making process has not met the requirements of the Equality Act 2010 and could be illegal.

The guidance in question from Transport Scotland may be seen here . In particular I would draw your attention to para 16 :-

16.Another study looking at the effect of speeds on overall accident numbers found a clear relationship. On the types of urban road likely to be considered for a 20 mph speed limit the study found the accidents could be expected to fall by between 4% and 6% for each 1 mph reduction in average speed. The greatest reductions were achievable on “busy main roads in towns with high levels of pedestrian activity”

The guidance therefore specifically includes roads which are specifically excluded from consideration in the Dundee report.

Within the guidance there is a particular paragraph which itemises the number of factors to be taken into account when setting speed limits :-

34.A number of factors should be taken into account when making an assessment about whether to introduce a 20 mph speed limit, which include - but are not restricted to - the following:-

  • road/street functions –including whether streets contain shops or are mainly residential, volumes of traffic, bus services, local access, formal walking and cycling routes, etc. As outlined in Designing Streets22 street design must consider ‘place’ before ‘movement’.
  • composition of road users - including existing and potential levels of vulnerable road users
  • existing traffic speed; and
  • accident data - including frequency, severity, types and causes;
  • road environment - including width of road and footway, sightlines, bends, junctions, pedestrian crossings, etc;
  • local community - including consultation with police, other emergency services, public transport providers and impact on residents (e.g. usage of road, parking facilities, noise and air quality) 

You will note that only one of these relates to the “road/street function and even in this recognises the presence of shops, formal walking and cycling routes and particularly that “place” must be considered before “movement”.

Any policy which arbitrarily excludes the consideration of a 20mph limit purely on the basis of a road being part of a “principal road network” cannot be within the guidelines. Hence it is completely wrong to state as in para 4.3 of the report that officers have followed this guidance in its recommendations.

Strategic roads and bus operators

The assertion in 4.5 that more strategic roads are important to the city and require the movement of HGV’s, Public Transport and Emergency vehicles is irrelevant. No-one is requiring such vehicles to stop using those roads, but merely that they operate within a speed limit that takes into account the needs of vulnerable road users and the community at large.

It is interesting to note that both National Express and Stagecoach acknowledge that “ there could be benefits in road safety terms from the implementation of 20mph limits in residential areas” It is difficult to conclude that these same benefits would not also occur on “principal roads” and bus corridors. As “commercial organisations” they not only have a duty to their shareholders, but also to their customers and the public at large. Any trade-off in know road safety improvements for commercial profit must be rigorously determined rather than “brushing aside” any reduction in limit due to a potential change in route timings.  Indeed in other implementations in the UK bus companies First and Stagecoach were supportive of 20mph limits particularly as 20mph helps with their own Health and Safety objectives.

Note that a report by PTEG showed that on bus routes on primary city routes the time spent above 20mph was minimal. (See It comprised just 22% of the time spent travelling. Hence it is difficult to see how any reduction in peak speed would cause any major upset to timetables. If so this would primarily be at non-peak times when the actual speed will be effected far less. In fact for buses pulling into a stream of traffic after stopping then there are considerable benefits from that stream of traffic being slower.

We would note that often bus companies will respond negatively to any attempts by local authorities to impose any conditions on their service. This is often a reaction that tend to over estimate any negative aspects in the hope of obtaining further concessions such as dedicated bus lanes, etc. Hence any such objections should be reviewed robustly, especially if going against national government guidelines.

The significance of 24mph average speeds

In 4.7 the report states :-

“Scottish Government guidance indicates that any roads with average speeds above 24mph would require speed reducing measures as signage alone will not reduce traffic speeds sufficiently.

This is incorrect. Such a statement DOES NOT EXIST IN THE GUIDANCE. It misleads readers and councillors.

The Scottish Guidance actually says :-

“However, without additional traffic calming, it is recommended that 20 mph limits should primarily be considered where existing mean speeds are no greater than 24 mph.”

The guidance also notes with regard to the Edinburgh implementation :-

55.The City of Edinburgh Council pilot showed that locations with an initial mean speed higher than 24 mph generally experienced the highest drops in speeds. It can therefore be appropriate to impose 20 mph limits on some streets with a mean speed of higher than 24 mph, in a context of other nearby streets with lower existing averages. This can have the benefit of avoiding a piecemeal speed network in a predominantly 20 mph limit area.

And in reference to the Edinburgh results :-

3. In the 12 locations where the mean speed prior to the introduction of the pilot scheme exceeded 24 mph, there was an average drop of 3.3 mph to 22.4 mph (the 85th percentile speed on these streets fell by 3.9 mph to 26.0 mph).

On this issue it is possible that the report would be misdirecting members in their decision making process.

Note that the inclusion of principal routes within a scheme often results in reduction in the number of boundary signs and hence the cost of implementation.

Note that we are not saying that ALL principal routes should be set at 20mph. But we are saying that to arbitrarily exclude any such routes based on the misinformation in this report, including the unfounded comments from commercial bus companies and without a reference to effect on those with protected characteristics such as age and disability.


Throughout the UK cities and towns are using the revised and supportive national guidance on setting urban speed limits to create better conditions for all by wide-area 20mph limits. These already include most of the iconic cities in the UK. In doing so many are including arterial routes where a sense of “place and people” is seen as far more important than “vehicle movement”. In doing so they are responding to central government, their own particular needs to meet council objectives for air quality, modal shift, road danger reduction and community aspirations.

This report misdirects and misrepresents both Transport Scotland guidance and the implications of the recommended policy on how it meets Equality Act law. Members of the committee should certainly reject the report and its recommendations and seek a more informed and objective point of view before deliberating this issue any further. If I can help in any way then I would be pleased to do so.

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