fanf: (dotat)
[personal profile] fanf

In Britain there is a standard for tactile paving at the start and end of shared-use foot / cycling paths. It uses a short section of ridged paving slabs which can be laid with the ridges either along the direction of the path or across the direction of the path, to indicate which side is reserved for which mode of transport.

Transverse ridges

If you have small hard wheels, like many pushchairs or the front castors on many wheelchairs, transverse ridges are very bumpy and uncomfortable.

If you have large pneumatic wheels, like a bike, the wheel can ride over the ridges so it doesn't feel the bumps.

Transverse ridges are better for bikes

Longitudinal ridges

If you have two wheels and the ground is a bit slippery, longitudinal ridges can have a tramline effect which disrupts you steering and therefore balance, so they are less safe.

If you have four wheels, the tramline effect can't disrupt your balance and can be nice and smooth.

Longitudinal ridges are better for pushchairs

The standard

So obviously the standard is transverse ridges for the footway, and longitudinal ridges for the cycleway.

(I have a followup item with a plausible explanation!)

Date: 2016-06-13 08:46 am (UTC)
lnr: (Pen-y-ghent)
From: [personal profile] lnr
This has done my head in for years too! I wonder who came up with it, and if it's even *possible* to safely change it in retrospect.

Date: 2016-06-13 09:36 am (UTC)
rmc28: Rachel smiling against background of trees, with newly-cut short hair (Default)
From: [personal profile] rmc28
You'd have to repaint / re-lay all the cycle lanes ...

Date: 2016-06-13 01:05 pm (UTC)
lnr: (Pen-y-ghent)
From: [personal profile] lnr
Yeah, I can't see any way you could do that across the whole country without having a confusing mishmash for a while - which would presumably completely confuse those who actually rely on them.

Date: 2016-06-13 04:02 pm (UTC)
From: [identity profile]
Well, it doesn't sound like "the other way round" is perfect either, you'd have to choose some OTHER distinguishable configuration, ideally one more comfy for bikes and pushchairs, if possible, and change the that a bit at a time...

Date: 2016-06-13 04:53 pm (UTC)
From: [identity profile]
I'm sorry, I don't understand how you read my comment? Clearly the current convention is awful and the reverse would be better. But is that the best possible convention? I don't know, but not necessarily. Is it the least intrusive? I don't know. Would it line up with the convention used at crossings and dropped curbs? I'm don't know. Are ridges (rather than some pattern of dots, or some other pattern) the best pattern? I don't know.

If the reverse of the current situation is the only possible sensible configuration, then yes, there's no good option. But if some other configuration is better than either, and sufficiently different it's not confusing, then we could use that for new installations. Then there would be a long transition period, but at least once you were familiar with the types one particular piece of it would be unambiguous. You would avoid the problems of "sometimes it means this, sometimes it means the opposite" and "have to relay them simultaneously all over the country".

I'm not sure if you already knew no other configuration would work, or read my post as the opposite of what I was trying to say?

Date: 2016-06-14 06:35 am (UTC)
From: [identity profile]
(And you'd also avoid the problem of, the current standard is an international standard, and while in the UK one drives on the left rather than the right I'm not convinced the downsides of deliberately going counter said international standard are worth it...)

Date: 2016-06-15 07:44 am (UTC)
From: [identity profile]
I'm really sorry, I got the impression from fanf's post that part of the problem was the current standard WASN'T compatible with standards elsewhere (either different sorts of paving in the same country, or internationally). If it is worldwide, obv there's a really high cost to doing it differently.

Date: 2016-06-15 08:13 am (UTC)
From: [identity profile]
Ah! Sorry, I was thinking of your summary of Clive's comment. It sounded like, even if the ridges were reversed, they'd still be somewhat inconsistent, whereas now I look closer, you were implying that it would be more consistent if they were reversed.

But it still sounds like they wouldn't be completely clear. The cycleway isn't really "walk with caution", it's more like "don't walk here at all" (at least in longwise, you could cross sideways).

I'm still not sure where I went wrong. I feel like the conversation was:

Tony: This would be better the other way round.
Lnr: But it would be hard to change because if you swap some of them over, then they're always ambiguous.
Jack: But even if they're better the other way round, they're still somewhat uncomfortable. maybe some OTHER design would BOTH be more comfortable AND be safe to install incrementally without making the meaning ambiguous.
Everyone: NO!

Date: 2016-06-15 09:23 am (UTC)
From: [identity profile]
And sorry, I think I was too grumpy today. It's not a disaster if we ended up at cross purposes, I was just frustrated trying to work out what was actually going on.

Date: 2016-06-15 05:01 am (UTC)
lnr: (Pen-y-ghent)
From: [personal profile] lnr
It certainly read to me like you thought there was an actual *problem* with the other way round, apart from the fact it's almost impossible to get there from here.

Date: 2016-06-15 07:55 am (UTC)
From: [identity profile]
I guess. I mean, I meant I HOPED there was a problem with the other way round, because then if the best standard is some type of paving that has a tactile surface other than the ridges, we CAN adopt it incrementally, and never face the problem of "there's ridges -- but do they mean bikes (old way) or feet (new way)". But apparently "it's not perfect" sounded like "lets immediately give up and not change anything"?

Date: 2016-06-13 08:55 am (UTC)
aldabra: (ghost)
From: [personal profile] aldabra
*Yes*. There is an age-of-kid at which the *only* reason you're out is that they will only sleep in a moving pushchair, and you've been up 23 hours, and you'd rather be walking in the rain than being screamed at at home. The absolute last thing you want is gratuitous bumps.

Date: 2016-06-13 08:55 am (UTC)
From: [identity profile]
*sigh* I wonder if the ridges could be made narrower, to be less wheel-invasive, but still equally tactile?

Date: 2016-06-13 10:17 am (UTC)
From: [identity profile]
Ah! I was wondering if they matched up or not -- I remembered something about the direction of the strips at crossings and such-like, but not enough.

Date: 2016-06-13 11:45 am (UTC)
From: [identity profile]
A SOURCE OF ONGOING FRUSTRATION TO ME, yes. I am glad to know that it is shared.

Date: 2016-06-13 12:25 pm (UTC)
From: [identity profile]
Very much so, from my perspective -- on bad pain days tactile paving as it's set up can cause actual minor screaming, which is pleasant for precisely nobody. Even when I'm not having a bad day it's still not exactly pleasant (even with front-fork suspension), so in fact I normally do just end up switching to the cycle lane until I'm past the Incorrect Ridges.

Date: 2016-06-13 12:40 pm (UTC)
From: [identity profile]
Oooh, you have thereby reminded me that actually probably one of the sets of people to Complain Loudly At about this are PAMELA, part of the UCL transport institute -- they do a lot of work on making the tube e.g. accessible and were (I believe, or perhaps it was the parent department) instrumental in the "shared usage" design of Exhibition Road (the one with the NHM/Science Museum/V&A/Imperial on). Hmm!

(I am aware of them because I've participated in a couple of their pilot studies about how to meaningfully do motion capture on wheelchair users, in the interests of getting a better sense of how we interact with public spaces/transport/etc - they have an excellent set-up for testing all this stuff...)

Date: 2016-06-13 02:19 pm (UTC)
From: [identity profile]
This is the same kind of ignorance that leads to the use of transverse ridges to slow down cyclists. (You'll recall when this happened a few years ago on the Ditton Meadows bridge.) On a bicycle, the faster you go, the less unpleasant vibration you get, and so the natural instinct is to speed up as you approach them.

How we do it here

Date: 2016-06-14 12:15 am (UTC)
From: (Anonymous)
The standard here seems to be (I haven't checked design specifications) Portland Cement Concrete for the pedestrian parts and Bituminous Concrete (blacktop, tarmac, "asphalt") for the cycle parts. Sometimes instead of cast-in-place PCC they use 4x4 or 6x6 concrete pavers.

On the street where my office is located, there's a "cycletrack", and I got to see how this was built. The cycletrack, curbside tree/street furniture RoW, and pedestrian walkway are all built on top of a unitary cast-in-place PCC "bathtub". This is then covered with a layer of blacktop which forms the base layer for the pavers. Once the pavers are installed and locked together with polymeric sand, another layer of blacktop is laid between two stringer courses to make the cycletrack, which is then painted with arrows and cycle icons.

Date: 2016-06-14 07:21 am (UTC)
bens_dad: (Default)
From: [personal profile] bens_dad
> Transverse ridges are better for bikes
> Longitudinal ridges are better for pushchairs

Longitudinal ridges oppose side-slip, which is more dangerous to those on two wheels.
When climbing a hill, transverse ridges give better traction; a bike is likely to have some momentum to carry it through the market slabs, whereas a push-chair is likely to stop more quickly without power.

Or at least that was the rationale I deduced upon finding the slabs at the Nuffield Gym (nee Greens) end of the Coldhams Lane railway bridge, where traffic has either just turned left or sharp right when it meets the ribbed paving.

It is not obvious to me that either direction of tile is obviously better or worse for two than four wheels in all, or even most, situations.

Date: 2016-06-15 05:10 am (UTC)
lnr: (Pen-y-ghent)
From: [personal profile] lnr
Do you ride a bike? Longitudinal ridges are awful unless you're perfectly straight on and don't bump into them. Otherwise they tend to push your wheel away from the direction it was going into the direction of the ridge, and can cause scary wobbles, or worse.

A bit of googling finds me this interesting small paper:

"Almost one fifth of the crashes [caused by the road surface] resulted from longitudinal grooves or raised edges in the road surface. A wheel can easily skid when crossing raised edges or tram rails at too small
an angle. The front wheel skidded and got stuck in the tram rails in a few cases. "

Date: 2016-06-14 07:36 pm (UTC)
From: [identity profile]
Maybe they could inexpensively correct this by painting out the bicycle symbol and repaint it on the other side, and put a sticker with the symbols reversed on the 'lollipop' sign until there was funding for a new sign?

That is, if they wanted to. I'm guessing they had some reason for this, although I can't see it.

Date: 2016-06-15 05:05 am (UTC)
lnr: (Pen-y-ghent)
From: [personal profile] lnr
If it was in one location sure, but this is the standard across the whole country - I doubt it's easy to even locate all the places these are used in one city, never mind everywhere. And to change them all at the same time, so it's still safe for those who actually use the tactile paving to tell which is which?

Date: 2016-06-15 06:17 am (UTC)
From: [identity profile]
The tactile paving is aiui for blind people to know which side to use. Blind people can not read the sign! Also it is an international standard, so confusion would result.
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