The Importance of Highway Safety in Planning Decisions
Highway safety in planning applications: understand highway standards, visibility splays, accident records and how to address highway objections.
PLANNING APPLICATIONS
Andrew Ransome
9/2/20265 min read
Highway safety is one of the most common transport issues raised in planning applications.
It can also be one of the most misunderstood.
A highway objection does not always mean that a development is unsafe. Equally, the absence of accident records does not automatically mean that an access is safe.
The key is to look at the evidence and apply the correct standards to the site.
This article explains how highway safety is considered in planning decisions. It also looks at visibility splays, accident records, highway authority advice and the approach now set out in the August 2026 National Planning Policy Framework (NPPF).
What does the NPPF say about highway safety?
The latest NPPF places transport at the heart of the planning process.
Policy TR3 requires development to support sustainable patterns of movement. Development should be located where it can make effective use of existing or proposed transport infrastructure.
It also states that significant adverse impacts on the transport network or highway safety should be mitigated to an acceptable degree.
This is described as a vision-led approach.
Policy TR4 deals with street design, access and parking.
It requires transport considerations to be integral to the design of development. Streets and routes should create places that are safe, inclusive and attractive.
The policy also seeks to reduce conflicts between pedestrians, cyclists and vehicles.
For larger schemes, Policy TR6 deals specifically with transport impacts.
Where a development is likely to generate significant movement, it should be supported by an appropriate Transport Statement or Transport Assessment. A Travel Plan may also be required.
The assessment should consider reasonable future scenarios. This includes relevant times of day, cumulative impacts and different modes of transport.
Most importantly, Policy TR6 states that development should be refused where it would have a severe adverse impact on the transport network or an unacceptable impact on highway safety.
This is subject to consideration of proposed mitigation and wider network improvements. The policy applies during both construction and operation.
Choosing the correct highway standard
One of the most important issues is choosing the right design standard.
A common source of disagreement is the application of standards that are not appropriate for the road in question.
The main guidance includes:
Manual for Streets (MfS);
Manual for Streets 2 (MfS2); and
the Design Manual for Roads and Bridges (DMRB).
DMRB is primarily concerned with the design and operation of motorways and trunk roads.
Manual for Streets is particularly important for residential streets and other streets where place-making is an important consideration.
The correct standard will depend on the type and function of the road. It should not be selected simply because it produces the most conservative result.
This can be important when considering access arrangements, visibility and road geometry.
Visibility splays
For smaller developments, the key highway safety question is often whether vehicles can enter and leave the site safely.
Visibility splays are therefore important.
They are normally expressed using X and Y distances.
The X distance relates to the distance back from the give-way line. The Y distance relates to the distance a driver can see along the road.
The appropriate distances will depend on the circumstances of the site. They can include factors such as traffic speed, road geometry and the type of access.
Speed surveys may therefore be required.
Pedestrian visibility should also be considered.
A vehicle may have adequate visibility of the road but still have poor visibility of pedestrians using the footway.
This is particularly important where children, cyclists or people with limited mobility may use the route.
Does an accident-free road mean it is safe?
Not necessarily.
This is an argument that can sometimes appear in planning representations.
A lack of recorded accidents does not prove that a junction or access is safe.
Police accident records generally relate to reported personal-injury collisions. They do not capture every near miss or minor incident.
However, the opposite argument is also important.
A departure from a recommended visibility standard does not automatically mean that a proposal is unsafe.
Highway safety needs to be considered in the context of the site.
The evidence should be examined as a whole. This can include road speed, traffic conditions, visibility, road geometry, pedestrian movements and the nature of the proposed development.
What weight should be given to the highway authority?
Highway authority advice is an important material consideration.
However, it is not an automatic veto. The planning decision must be based on the evidence. This means that a highway objection can be challenged where there is strong technical evidence to the contrary.
For example, this might include:
a properly conducted speed survey;
a detailed visibility assessment;
independent transport evidence; or
an alternative access design.
The strength of the evidence will be critical.
What should you do if there is a highway objection?
Highway issues are best addressed at an early stage.
If a proposal is facing a highway objection, it is worth asking three questions.
First, is the correct highway standard being applied?
The standard should reflect the type and function of the road.
Second, is the technical evidence robust?
This might include speed surveys, visibility calculations and traffic data.
Third, is the objection actually about highway safety?
There can sometimes be a difference between a genuine safety concern and concerns about traffic levels, congestion or inconvenience.
These are not necessarily the same planning issue.
The latest NPPF also makes clear that transport impacts should be considered in the round. This includes sustainable travel, cumulative impacts and the wider transport network.
Highway safety should be considered early
Highway safety should not be treated as an issue to resolve at the end of the planning process.
The new NPPF promotes early consideration of transport and sustainable movement.
This can help identify problems before an application is submitted. It can also allow changes to the access, layout or supporting evidence to be made at an early stage.
A well-designed scheme should therefore consider highway safety alongside the other planning issues from the outset.
Need planning advice on site?
If you are preparing a planning application, or dealing with a highway objection, I can advise on the planning implications and the most appropriate way forward.
Where specialist technical input is needed, I work with a team of experienced transport and highway consultants who can provide the necessary assessments and technical advice.
This means that highway issues can be considered as part of a wider planning strategy, rather than in isolation.
If your proposal involves highway access, visibility, traffic or road safety issues, get in touch to discuss your site and the planning options available.
Andrew Ransome MRTPI - Email: andrew@andrewransome.co.uk
About me
Andrew Ransome is a Planning Director and a Chartered Member of the Royal Town Planning Institute (RTPI), with more than two decades of experience in town planning.
He specialises in delivering strategic planning solutions for complex developments across both rural and urban environments, helping clients navigate planning challenges and unlock development opportunities. Connect with Andrew on Linkedin.
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Get in touch for planning advice: Email: andrew@andrewransome.co.uk
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