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> What is ramp metering? (The Bay Area contingent of HN can answer that!) Traffic lights (typically red/green only) at the bottom of on-ramps that rate-limit (
by deathanatos 9y ago
> What is ramp metering?
(The Bay Area contingent of HN can answer that!) Traffic lights (typically red/green only) at the bottom of on-ramps that rate-limit ("meter") traffic onto the freeway, typically during rush hour. You drive up to a red, stop, it turns green and you go. (Sometimes a sign indicates that 2 cars get to go per green given.) There are usually sensors embedded in the rightmost lane of the freeway shortly before the merge point, and on a good day, it feels like it gives you a green timed with a gap. (Although I think it also sometimes just times out and lets you go, in which case, no gap.)
The ones here have an HOV lane and a non-HOV lane, usually; typically they just force the HOV lane to come to a near stop before turning green; I think that's more to slow the HOV traffic down to avoid collisions with the adjoining non-HOV lane should their light also turn green, but it feels like a weird formality when driving it. Some days the cops sit on the ramp pulling people cheating in the HOV lane.
https://en.wikipedia.org/wiki/Ramp_meter https://en.wikipedia.org/wiki/Ramp_meter
It is one of the two things I warn family visiting that have never visited before. (In the majority of the US, you just get on the highway, there isn't a traffic light at the bottom of a ramp, that'd be absurd, since you're wanting to accelerate to ~70mph.) (The other is lane splitting: motorcycles will (ab)use the dividing line, particularly between lanes 1 & 2, to pass.)
- flomo 9y agoOn a similar note: > Did you know that the long pointy triangle thing is called a “gore”? > Well, you might survive, because there is a thing there that is designed to crush when you hit it. It might be a QuadGuard Elite Crash Cushion System Or it might be the traditional solution, which is a bunch of rubbermaid garbage pails filled with water. (Not that long ago, I was trying to let someone merge in front of me, but they couldn't make up their minds and ended up slamming their brakes into the gore. I bet they had fun getting out of there.)
- notatoad 9y ago>Or it might be the traditional solution, which is a bunch of rubbermaid garbage pails filled with water. only if you live in a place where water doesn't freeze
- StudentStuff 9y agoPretty common on the West Coast, even in Seattle.
- Johnny555 9y agoI assumed they used antifreeze in places where it freezes. Maybe not applicable in extreme cold, but seems to be good down to -40 or so. http://www.dot.ca.gov/hq/esc/oe/project_ads_addenda/05/05-0T0004/supplemental_info/05-0T0004IH.pdf http://www.dot.ca.gov/hq/esc/oe/project_ads_addenda/05/05-0T... Some customers have indicated that common deicing and dust control chemicals that are used on the highway make excellent choices for antifreeze agents. These include: * Calcium Chloride (CaCl2) * Calcium Magnesium Acetate (CMA) * Potassium Acetate (KAc)
- lfowles 9y agoI've seen sand used as well as water.
- lfowles 9y agoI skimmed the comments here before reading the article and was curious what a "gore" looked like. After a seconds pause, I decided I should get on with reading the article instead of searching for "highway gore" :)
- erroneousfunk 9y agoFun fact, the the triangular piece in a clothing pattern used to add shape/dimensionality is also called a gore.
- defen 9y agoI believe it all derives from heraldry: https://en.wikipedia.org/wiki/Gore_(heraldry) https://en.wikipedia.org/wiki/Gore_(heraldry) From Old English gār (spear): https://en.wiktionary.org/wiki/gar#Old_English https://en.wiktionary.org/wiki/gar#Old_English
- greenyoda 9y agoIn the NYC area, we also have some on-ramps with red/green traffic lights. However, these are only active during peak traffic times, and are otherwise turned off.
- ubernostrum 9y agoThey are similarly active only during peak hours in CA. Usually, at the entrance to the ramp from whatever road feeds it, there's also a sign that lights up flashing to tell you the metering is on, so you know you can expect to stop ahead.
- rachelbythebay 9y agoLinger long enough without going and you'll probably see a yellow at a metering light.
- Shivetya 9y agoyou can find a map on this site https://ops.fhwa.dot.gov/freewaymgmt/ramp_metering/index.htm https://ops.fhwa.dot.gov/freewaymgmt/ramp_metering/index.htm which shows where it has been implemented; Atlanta area where I am has an extensive amount of this and HOV systems, and express(toll) lanes.
- compuguy 9y agoIn the Washington DC area, we have some on ramps that are metered (I-66 inside the beltway, and I-395) come to mind.