Crawler lanes - when do you need them?

[saaby93]

Driving about the countryside from time to time you find a crawler lane on a hill on a motorway or dual carriageway
Is there a particular gradient or road that you need one? Is it say 10% ?

Are there any design rules for when they run out?
You see them ending at the top of the hill but for safety reasons hatched off a few hundred yards early yet waht you really need is for them to continue for half a mile past the brow for slow traffic to have time to get back up to speed.

[anonymous-user]

http://www.standardsforhighways.co.uk/ha/standards...

Part 1, TD9, Chapter 5.

Its very dry.

[saaby93]

thanks Bob
Begin considering at 2% and a length of 500metres - it's surprising there arent more of them

[Vlad the Imp]

Blimey, DMRB Volume 6 is dull, I’m more of a Volume 7 man myself, that’s where the proper interesting stuff is!

[saaby93]

OpulentBob said:

http://www.standardsforhighways.co.uk/ha/standards...

Part 1, TD9, Chapter 5.

Its very dry.

It's not bad
Are there any places with a slip road off mid crawler lane?

[anonymous-user]

saaby93 said:

OpulentBob said:

http://www.standardsforhighways.co.uk/ha/standards...

Part 1, TD9, Chapter 5.

Its very dry.

It's not bad
Are there any places with a slip road off mid crawler lane?

I can't think of any. There are exit (off) slips close to lane gains, such as the A12 southbound just before Brentwood, and I know of a layby next to a crawler lane, but can't think of any exact matches. My motorway knowledge runs out west and north of London though...

[anonymous-user]

Saaby where you based? You are suitably interested in all this stuff, you'd probably make a good infrastructure engineer. Want a job? I'd have to put you in your own office though, no offence

[saaby93]

OpulentBob said:

Saaby where you based? You are suitably interested in all this stuff, you'd probably make a good infrastructure engineer. Want a job? I'd have to put you in your own office though, no offence

[saaby93]

OpulentBob said:

saaby93 said:

OpulentBob said:

http://www.standardsforhighways.co.uk/ha/standards...

Part 1, TD9, Chapter 5.

Its very dry.

It's not bad
Are there any places with a slip road off mid crawler lane?

I can't think of any. There are exit (off) slips close to lane gains, such as the A12 southbound just before Brentwood, and I know of a layby next to a crawler lane, but can't think of any exact matches. My motorway knowledge runs out west and north of London though...

layby A12
https://www.google.com/maps/@51.6254835,0.2868324,...

[anonymous-user]

saaby93 said:

OpulentBob said:

saaby93 said:

OpulentBob said:

http://www.standardsforhighways.co.uk/ha/standards...

Part 1, TD9, Chapter 5.

Its very dry.

It's not bad
Are there any places with a slip road off mid crawler lane?

I can't think of any. There are exit (off) slips close to lane gains, such as the A12 southbound just before Brentwood, and I know of a layby next to a crawler lane, but can't think of any exact matches. My motorway knowledge runs out west and north of London though...

layby A12
https://www.google.com/maps/@51.6254835,0.2868324,...

Nope that's a ghosted Type A (modified) layby. The (modified) refers to the merge length on exit. No island (iirc) because it's used a lot by VOSA and HGVs and it helps with vehicle tracking in and out.

The layby next to the crawler lane is here on the A120:
https://www.google.com/maps/@51.8872015,0.1536173,...

Here's the lane gain next to a slip but it's not really the type of thing you were asking about:
https://www.google.com/maps/@51.6686365,0.3736949,...

[Vlad the Imp]

I think the M4 eastbound and Junction 18 might qualify as a crawler lane with an offslip in it?