Visibility splays for non-right-angles

[Drellingore]

Does anyone have experience of calculating visibility splays and requesting news accesses for shallow angles?

 

We might want to ask for a new access to join a single-track country lane at a very steep/shallow (depending how you measure it) angle. All the guidance and diagrams I can find relate to cases in which an access joins a larger road at a right angle. 

 

In this really high-quality diagram, the red bit is the country lane, and the blue bit is the potential access:

Presumably in this case people would be using their wing mirrors. Is this allowed/catered for anywhere in the guidance? Or would the county council highways department likely throw it out because at the angle of approach, you wouldn't be able to see traffic from the left without mirrors?

[JohnMo]

You need to look at your local regs, our, when on a single track road you have to form almost a layby so delivery vans etc. can stop without blocking the road. You would have to look at that and see if what you propose is practical.

[Drellingore]

1 minute ago, JohnMo said:

You need to look at your local regs

 

Thanks! Any idea where I might find those? I'm intimately acquainted with my district council's local plan, but I'm guessing this is somewhere else. The Kent Design Guide touches on it, but sadly doesn't go into detail about angles or mirrors.

[JohnMo]

It may be the roads people

[joe90]

No mention of non 90’ drives.  https://www.kent.gov.uk/__data/assets/pdf_file/0006/13011/Making-it-Happen-G2-Design-standards-residential-and-industrial.pdf   They only say visibility must be X meters, visibility IMO can be achieved with mirrors. If they refuse ask them to cite the regs that say so. If they do refuse can you not turn the last few meters to be 90’.

 

[garrymartin]

The Manual for Streets shows how to draw and calculate visibility splays. Page 93 shows you how to draw visibility splay lines when the roads don't meet at 90 degrees. Looks like you need a combination of (b) and (c) to draw your lines

 

https://assets.publishing.service.gov.uk/media/5a7e0035ed915d74e6223743/pdfmanforstreets.pdf

 

But there are probably other guidelines about safety when turning left out of the junction or right into it. Best to speak to your local Highways Department.

[joe90]

19 hours ago, garrymartin said:

Page 93 shows you how to draw visibility splay lines

But that is for road junctions not drive access! I had to fight to get highways out to see my proposed 90’ drive access with full visibility splays and when they did they would not recommend it to planning, they would only “not object” beggars belief (but I won in the end 👍). Might be worth contacting highways in your area fir guidance.

[garrymartin]

6 minutes ago, joe90 said:

But that is for road junctions not drive access!

I had assumed from the wording (possibly incorrectly) that @Drellingore was suggesting a new access road rather than a direct frontage access.

[joe90]

1 minute ago, garrymartin said:

suggesting a new access road

Ah, only @Drellingore can answer that one but I assumed private drive 🤷‍♂️

[Drellingore]

Ha, it's kinda both. A neighbouring farmer has a right-of-access along a strip of the site where the adjacent lane is too narrow for him to be able to get his machinery through. So it's almost like a slip road for farming lorries. It isn't actively used, and he only intends to ever use it if his current access via a rented field is rescinded. 

[saveasteading]

If it is a new access then it must comply with the highway design rules.

If it is an existing, but inferior, access then they tend to let it go. 

If it was angled the other way then it would be reasonably safe turning left but horrible turning right. 

Yours looks rather scary to me unless potholes are slowing the traffic.

[joe90]

9 minutes ago, Drellingore said:

Ha, it's kinda both

Well it’s not a public road so I guess it would be treated as a “drive” that someone else has access too. Still might be worth contacting highways for guidance I guess, but could you say it was “existing”?

Edited May 2, 2024 by joe90

[garrymartin]

The magic wording in planning is usually "new or intensified" although rather frustratingly, "intensified" isn't defined in law so is subject to some interpretation.

 

So even if the access was "existing", its use would be very infrequent access for farm machinery. If then used to access a dwelling, I'm pretty sure the local Highways department would see that as intensification and would want to see adherence to their design standards and would at that point indicate whether they see it as a "drive" for direct frontage access or an "access road".

 

I found my local Highways department to be reasonable about general advice, but unwilling to be drawn into definitive statements outside of formal pre-application advice, and even then, with no guarantee that their response to a planning application would be consistent.

 

But having said that, I do think you'll need to bite the bullet and ask their advice.

 

 

 

 

[Temp]

On 01/05/2024 at 12:57, joe90 said:

visibility IMO can be achieved with mirrors. 

 

They may want you to prove you have a right to install a mirror. 

[joe90]

11 hours ago, Temp said:

 

They may want you to prove you have a right to install a mirror. 

Ah, I meant car mirrors (I have a junction near me where I use a door mirror to see if the road is clear)

[Drellingore]

35 minutes ago, joe90 said:

Ah, I meant car mirrors

 

Same here  Although a good point about pole-mounted ones.