The sidewalk doesn’t have chickenpox.

June 19, 2018 3:33 PM

Ever wonder what those bumps in the sidewalk are for when you’re approaching an intersection? Dr. Amy Kavanaugh explains in this twitter thread.
posted by jenkinsEar (29 comments total)

This was really interesting. Thanks.
posted by Orlop at 3:42 PM on June 19, 2018 [2 favorites]

Street braille!
posted by SonInLawOfSam at 4:08 PM on June 19, 2018 [2 favorites]

Interesting. I always assumed those were designed to stop wheeled things, like shopping carts and wheelchairs, so that they don’t accidentally roll into intersections.
posted by dephlogisticated at 4:12 PM on June 19, 2018 [1 favorite]

i don't see these in California - they look walkable and cool, what a useful purpose.

but the bright yellow bumps that are on the accessible slopes of sidewalks, tho - they are seemingly there to break ankles and act like banana peels to any hard-soled shoe that ventures near.
posted by lapolla at 4:17 PM on June 19, 2018

Those concrete ones look nicer than the plastic ones they've been installing here in California/Bay Area. I want to say I've seen some that aren't fully attached to the ground (as in, they bubble or pop up slightly). Plus, when it rains, I always have a bit of worry that, despite the texture on the bumps, I'm going to slip and fall (but I'm pretty sure that's more an OCD-driven fear of the dirty, filthy ground).
posted by MikeKD at 4:22 PM on June 19, 2018

Cool! I've noticed these around Philadelphia recently and figured they were for visually impaired people, but ours don't have that clever L shape that leads you to the intersection -- just a plain red bumpy square in the curb cut.
posted by basalganglia at 4:27 PM on June 19, 2018 [3 favorites]

In the US, they're meant more as warning strips for VI people wherever their path of travel might intersect that of a vehicle or something similar, and that's pretty much it. In Denmark, at some tourist spots (I'm thinking Helsinborg specifically) there's a linear form that functions as a guide across large plazas, with the grid pattern at path intersections.
posted by LionIndex at 4:29 PM on June 19, 2018 [2 favorites]

The US ADA has gone back and forth on these. Last I checked they were now only required for locations like train platforms. Wheelchair users don't like them (natch), and they pose another set of issues for women in high heels.
posted by rudd135 at 4:32 PM on June 19, 2018

I'm happy for the people that they help, but they seriously took down my wife on a bike in the rain when she hit one at an angle on a bike-ped trail crossing. Super slippery.
posted by BrotherCaine at 4:47 PM on June 19, 2018

I was happy to learn the name of the bumpy stuff in English: blister paving. In French it has the equally delightful name of podotactile. Now you know!
posted by Liesl at 5:06 PM on June 19, 2018 [11 favorites]

Those concrete ones look nicer than the plastic ones they've been installing here in California/Bay Area.

The ones we have here in Toronto are made from cast iron. Under the accessible design standards used by most municipalities in Ontario to comply with the AODA (here are Ottawa's for example), they're called tactile walking strip indicators (TWSIs, or "twizzies" for short).

Part of the reason for using cast iron as a material is that TWSIs made from them can withstand being scraped by snow plows (obviously not a consideration in California). They're also waaaay less slippery when wet relative to the rubber ones. They look like this once they've developed their rusted coating (this is by design, BTW).
posted by mandolin conspiracy at 5:08 PM on June 19, 2018 [8 favorites]

Yeah we have these in NZ too - mainly plastic, very hard rubber and often slippery as, but tihs is NZ - find an early form of an idea, or find a good idea and do something wierd to it, then make it law.

A quick reading shows they are usually installed wrongly here anyway - they should be " perpendicular to the road so they can be used to align the feet" NZ Blind Foundation
posted by unearthed at 6:22 PM on June 19, 2018 [2 favorites]

Neat! Reminds me of some of these accommodations found in Dutch train stations: BBC clip
posted by stillmoving at 6:54 PM on June 19, 2018

This is a really good explanation of these. The ones in the US that I've seen don't have the L shape, which is a much better idea.
posted by LobsterMitten at 7:01 PM on June 19, 2018

This is very common in Japan, it's all over Tokyo.
posted by zardoz at 7:24 PM on June 19, 2018

Having read through a whole backlog of it, I have to say Amy Kavanaugh's Twitter feed is an absolute delight. Thanks for posting.
posted by mandolin conspiracy at 7:42 PM on June 19, 2018

I knew basically what these were for but not the details, that’s really interesting
posted by KateViolet at 11:43 PM on June 19, 2018

They've been installing these in Chicago for the last several years. Unfortunately I don't think they're doing it very well - now whenever it rains, every sidewalk intersection in my neighborhood becomes a small lake, often too big to easily jump over.
posted by dnash at 5:36 AM on June 20, 2018

They've been installing those all around here lately, I didn't know about visual impairment aspect of them.
posted by octothorpe at 6:13 AM on June 20, 2018

They are all over in my town too. I have drop foot and find them treacherous, but now that I know they help visually impaired folks I will try not to hate them so much.

They have also been putting in stamped concrete to look like bricks, for the crosswalks. Does this serve an ADA purpose of some kind as well, or is it just for looks?
posted by elizilla at 6:32 AM on June 20, 2018

I watched a special effects reel for the Netflix show Mindhunter and was impressed that they took the effort to remove all of these curb-cuts via CGI to fit in better with the 1970s setting.
posted by octothorpe at 6:42 AM on June 20, 2018 [1 favorite]

Austria has had these for a while, and they usually come with tactile markings on boxes at chest height that describe the layout of the street you’re about to cross (and double as an acoustical and/or vibrotactile walk signal at light-controlled pedestrian crossings). The example photo in the Wikipedia article says that you’re facing a kerb, two lanes of mixed traffic from the left, a refuge, trams from the right, three lanes of mixed traffic from the right, and another kerb. Here’s another example, for a kerb, cars coming from the left, a refuge, cars coming from the right, another kerb, and finally a bidirectional off-carriageway bicycle lane. They’re pretty fancy!
posted by wachhundfisch at 7:11 AM on June 20, 2018 [3 favorites]

Its great to learn stuff like this- a VI person was chatting to my kid recently about the little knobbly bit on the crossing button recently and he was fascinated. Like a poster upthread, I'd always assumed that the knobbles were for slowing down wheeled stuff so its interesting to hear about their primary purpose.
posted by threetwentytwo at 9:37 AM on June 20, 2018

Cool. I've only seen them on the sidewalk ramps. Thought they were for traction for wheelchairs and motorized wheelchairs.
posted by PJMoore at 9:51 AM on June 20, 2018 [1 favorite]

I never noticed the different arrangement between street tiles and the ones they just installed on our train platforms. I'll have to look for them next time.
posted by msbutah at 12:36 PM on June 20, 2018 [1 favorite]

Huh. Those are all over my neighborhood (at crosswalks, of course) and I always assumed they had something to do with providing traction in the wet or snowy/icy conditions. Their real use is far cooler.
posted by Thorzdad at 6:16 PM on June 20, 2018

This is fascinating and I’m so happy to have learned about it. I’ve spent the last few days looking at blister pavement here in the US and am bothered by its relative lack of systematicity. Might need to check out ways to volunteer with the ADA to push for better systems to serve both people with low vision and wheelchair users.

Thanks for posting, jenkinsEar!
posted by nicodine at 2:43 PM on June 21, 2018

In my area the bumpy sidewalk bits have been showing up on suburban streetcorners with no associated lights, as well as on the busier lighted intersections. Puzzlingly, I've had two separate neighbors tell me that "those bumpy things cost thirty thousand dollars apiece."

I wonder what they do cost? I'm guessing "more than concrete" and "way less than thirty grand." It was interesting to hear for sure what they're there for.
posted by Gilgamesh's Chauffeur at 9:23 PM on June 25, 2018

If you're talking about the bumps on the ramp, I have the answer to a related question. I don't know about the literal physical part, but here's a document talking about the cost of taking existing sidewalks without curb cuts/ramps and making them ADA compliant: https://www.documentcloud.org/documents/3534668-ADA-Curb-Ramp-Summary.html

The cost varies - it quotes a range of $6,000 to $22,800, typical range $9,000 to $19,000. Hilly areas cost more because there's a maximum slope for the ramp and approaching areas, so significant survey work and reconstructing the sidewalk around the area may become necessary. Soft costs, which I'm guessing means everything excepts materials and installation, average 40%, so $5,400 to $11,400 to actually construct them maybe?

Heaven help you if you end up needing to re-do the drainage for that bit of road, which will add a lot of expense real fast as you dig up the road and reconfigure pipes.

The costs for road changes get quoted as weird gotchas a lot because it's not obvious all the work that needs to go into it before you get to actual construction, and all the related changes that might need to happen once you look at changing one part. Here in Seattle, we recently had a downtown bike lane project that was widely publicized as costing $12 million per mile, but once you looked at what they were actually doing (completely rebuilding a road in the dense urban core, including drainage, new streetlights, etc) it made more sense and most of the work was unrelated to the bike lane itself.
posted by vibratory manner of working at 9:47 AM on June 27, 2018 [1 favorite]