Visibility Splay Assessments
Visibility assessments to support safe access design and planning applications
Adequate visibility is one of the most important considerations when designing or assessing a vehicle access. Whether you are proposing a new access, modifying an existing one or responding to Highway Authority comments during the planning process, demonstrating that drivers have sufficient visibility is fundamental to highway safety.
DW Transportation prepares Visibility Splay Assessments for residential, commercial and mixed-use developments throughout South Wales and across the UK. Our assessments provide clear technical evidence to support planning applications while identifying practical solutions where visibility constraints exist.
What Is a Visibility Splay Assessment?
A Visibility Splay Assessment examines whether drivers entering or leaving a site can see approaching traffic clearly enough to use the access safely. Although the concept appears straightforward, every site presents its own challenges. Road geometry, traffic speeds, boundary treatments, vegetation and changes in level can all influence the available visibility.
The purpose of the assessment is not simply to measure distances against published standards. It is to understand how the access operates in the context of the surrounding highway and determine whether any improvements or design changes are required.
When Is a Visibility Splay Assessment Required?
Visibility assessments are commonly requested by Local Planning Authorities and Highway Authorities whenever a development proposes a new vehicle access or changes to an existing one. They are equally important where an existing access has restricted visibility or where highway safety forms part of a planning objection.
Our experience ranges from individual dwellings and small residential developments through to commercial schemes, petrol filling stations and roadside developments where safe access arrangements are critical to the success of the project.
Our Approach
Every assessment begins with a detailed review of the site and the surrounding highway network. We consider the road layout, the characteristics of traffic using the road and any physical features that may affect visibility, before assessing the access against the appropriate highway guidance.
Where constraints are identified, our focus is on finding practical solutions rather than simply reporting a problem. In many cases, relatively minor changes to an access position, boundary treatment or site layout can significantly improve visibility and help overcome Highway Authority concerns before they delay the planning process.
Supporting Planning Applications
Visibility Splay Assessments are frequently prepared alongside Transport Statements, Transport Assessments and Access Design work. Considering visibility at an early stage allows potential issues to be identified before planning applications are submitted, reducing the likelihood of objections and unnecessary redesign.
Where required, we also prepare visibility drawings and provide technical responses to Highway Authority comments, ensuring that the assessment forms part of a coordinated transport planning strategy.
Why Choose DW Transportation?
DW Transportation has undertaken visibility assessments for a wide variety of developments across England and Wales. We understand that every site is different and that applying highway standards requires technical knowledge as well as professional judgement.
Our objective is always to provide proportionate, practical advice that supports safe development while helping clients navigate the planning process as efficiently as possible.
Frequently Asked Questions
What is a visibility splay?
A visibility splay is the clear area that allows drivers leaving a site to see approaching traffic, and approaching drivers to see vehicles emerging from the access. Maintaining adequate visibility is essential to ensure an access can operate safely. You can find out more in our Knowledge Hub.
When is a Visibility Splay Assessment required?
A Visibility Splay Assessment is commonly required where a new vehicle access is proposed, an existing access is altered, or highway safety forms part of a planning application. Planning Authorities and Highway Authorities often request visibility assessments before determining an application.
How are visibility splays measured?
The required visibility distances depend on several factors, including vehicle speeds, road characteristics and the relevant highway design guidance. Measurements are normally taken from a driver's eye position within the access towards approaching traffic in both directions.
What happens if there is insufficient visibility?
Restricted visibility does not always mean a development cannot proceed. In many cases, improvements such as repositioning an access, modifying boundary treatments or removing vegetation can improve visibility. Where constraints remain, we provide clear technical advice on the available options.
Do you carry out site visits?
Yes. Most Visibility Splay Assessments include a site visit to assess the existing highway conditions, identify physical constraints and take the measurements needed to prepare a robust technical assessment.
Can vegetation affect visibility?
Yes. Hedges, trees and other vegetation are one of the most common causes of restricted visibility. Where appropriate, we consider whether vegetation can be managed or whether alternative design solutions should be explored.
Do you prepare visibility drawings?
Yes. We can prepare visibility splay drawings to accompany planning applications, Transport Statements and Transport Assessments. These drawings clearly illustrate the available visibility and any improvements required or proposed.
Can you help if the Highway Authority has raised concerns about visibility?
Absolutely. We regularly prepare technical responses where visibility has been identified as an issue. This may involve reviewing the Highway Authority's comments, carrying out additional assessments and recommending practical measures to address any concerns.
Do you only assess new accesses?
No. We also assess existing accesses where changes are proposed, where planning permission is being sought for a change of use, or where highway safety concerns need to be investigated.
What types of developments do you assess?
We prepare Visibility Splay Assessments for a wide range of developments, including individual dwellings, residential developments, commercial premises, industrial sites, roadside developments, petrol filling stations and mixed-use schemes.