Mysterious islands in the street

May 17, 2012 3:49 PM

What is the purpose of very small median strips close to the sidewalk near an intersection?

With warm weather in my area, sidewalk repairs and improvements are going apace, and the local news hasn't caught up.

What is the purpose of a very small median strip or island, about 12-18 inches wide and 3-4 feet long, near an intersection of a main road and side street?

There is not enough space between this median and the curb for any car or bus. These medians have just been installed at two intersections that I know of. Is it for bicyclists, though I haven't found any exact parallels on Google Images? Or is it intended to slow traffic on a busy street? What are these medians called?

posted by bad grammar to travel & transportation around Washington, DC (15 answers total)

Do you have a picture of what you're describing?
posted by rhizome at 3:55 PM on May 17, 2012

Does it match any of these descriptions at http://en.wikipedia.org/wiki/Curb_extension ?
posted by channaher at 3:55 PM on May 17, 2012

These seem to be a new idea in urban locations. My guess, and it's a guess only, is to make vehicles commit to going straight or turning right, to avoid a last-minute change of mind that can disrupt things.
posted by yclipse at 3:55 PM on May 17, 2012

It sounds like maybe it serves as minor protection for cyclists from right-turning cars on a street otherwise without a buffered bike lane.
posted by threeants at 4:34 PM on May 17, 2012

My camera battery's run down. I may have a picture for you tomorrow. It is definitely not a curb extension, as it is detached from the curb and looks like a little barrier island.
posted by bad grammar at 4:57 PM on May 17, 2012 [1 favorite]

I think they are a traffic calming measure called a neckdown.
posted by OmieWise at 6:32 PM on May 17, 2012 [4 favorites]

Bumping the street out like that does slow cars down.

It also helps to put a crosswalk where the street is bumped out; pedestrians have a much shorter distance to cross the street, and it makes them more visible to motorists when they are waiting to cross.
posted by katinka-katinka at 7:26 PM on May 17, 2012

I think I have seen those, bad grammar, and I've assumed that they were curb extensions / neckdowns / whatever which were separated from the main sidewalk for other reasons — to keep stormwater runoff from puddling behind them, say; or because of something non-obvious about the construction technique or road subsurface the city uses.
posted by hattifattener at 8:34 PM on May 17, 2012

(The other benefit I've noticed to those things is that they prevent people from parking so close to the corner that you can't safely see approaching cross-traffic. It's illegal to park that close anyway, at least in my city, but it's rarely enforced.)
posted by hattifattener at 8:35 PM on May 17, 2012

Something kind of like this?
posted by clorox at 8:48 PM on May 17, 2012

There is a Dutch-origin means of creating a protected cycle path in an intersection [more], which is one thing your description sounds like. But you'd likely have other features showing it as a bike facility, such as painted lines/arrows, signage, or even a pavement difference.

I have seen "bump-outs" that are designed not to interrupt drainage and these tend to have a shallow concrete gutter on both sides -- but the bump-out itself is usually paved since these are urban conditions. That could be described as a separated median, I suppose.

In any case, this is an era of intense innovation in bike facilities, and I can also easily believe this has something to do with that even if it doesn't look exactly like anything else. But I still think you'd see other indications if that were the case.
posted by dhartung at 11:28 PM on May 17, 2012

Here are pictures of the thing.

Small street islands
posted by bad grammar at 4:18 PM on May 18, 2012

As you can now see from the picture, the islands most resemble OmieWise's neckdowns. The main street is often busy. A few months ago, a car jumped the curb and ran into two pedestrians on this sidewalk (about a block further down).
posted by bad grammar at 4:32 PM on May 18, 2012

I concur with OmieWise, and my middle paragraph is also in play as the separation appears to be so that existing drainage isn't interrupted.

Neckdowns
Neckdowns
posted by dhartung at 1:10 AM on May 19, 2012

From that photo I think it's a neckdown with a bike lane cut-out (I've found textual references to such in highway planning documents, but no photos; this is pretty close though). The photos dhartung links look like they're cut for drainage, not bicycles.
posted by hattifattener at 2:44 PM on May 19, 2012 [1 favorite]