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Comment by slg | Hacker News Reader

Is this a Bay Area specific thing? The terms "HOV lanes" and "carpool lanes" are used interchangeably in my experience. Are you just calling out separated lanes? The reason for the separation is that traffic in those lanes is often moving much faster than the other lanes which makes it very dangerous to give people the possibility of pulling into that lane unexpectedly. The ideal HOV/carpool lanes should have two lanes to allow passing and be separated from the rest of the lanes to promote safety. The 110 in Los Angeles is a great example and it uses the same transponders with switches that the article is discussing.

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In my experience, the vast majority of HOV/carpool lanes are single lanes, although some stretches like the 110 and the 91 are doubled up and are a much better experience. It's hard to believe the 405, of all places, is a single HOV lane and it bunches up pretty much continuously.

Although, on the 91, I don't know that it uses transponder settings since there's a dedicated "3+" lane when you approach reading areas, which are situated right in front of CHP buildings (so they can see if you're really 3+?)

They are synonyms, but parent is talking about separated roadway for HOV, that you can't merge into / out of at will.

Aren't all HOV lanes separated? Any that I've seen in Canada and the eastern US only allow you to merge at dedicated locations. The new ones on the 400 in Canada actually have a merge lane appears for a few hundred metres before shrinking down again, even though there's no physical barrier, it's all just paint.

I don't think that's the kind of separation they're talking about. It's technically illegal to cross that yellow line, but I've never heard of anyone getting in trouble for crossing out and back in to go around a grandpa going 45 in a 70. There are some HOV lanes in Florida that actually split into an entirely separate side road and some that have those soft rollover columns you can drive through but it will scratch up your car so it's really only for emergencies.

Exactly. There is a difference between not allowed to merge and not physically able to merge.

Merging not being allowed is still dangerous because people don't always follow the rules. It might even be more dangerous than lanes that always allow merging because then at least drivers in the faster lane can prepare themselves to expect merging.

A separated lane makes it impossible (or at the very least potentially damaging to the vehicle) to merge.

Here is an example of what I think is the ideal HOV setup[1]. There are two lanes so a single slow driver can be overtaken and there are physical dividers that prevent unexpected merging. You can also see the toll signs mentioned in the article that display the passenger number set on the transponders as discussed in the article.

[1] - https://www.google.com/maps/@33.9392023,-118.2796649,3a,75y,...

Yeah that's a pretty good HOV lane in my opinion (as a non city planner lol). Sometimes you still get two slowpokes side-by-side, but it's pretty rare.

No. There are several HOV facilities where it's just a regular lane, especially for 'part-time' HOV facilities (which are basically "this lane is HOV during rush hour, regular otherwise"). For example, HOV lanes on the NJT: https://goo.gl/maps/pKzjvAgFUhac1bva7

Before the changes talked about in this article, the HOV lanes on US101 in NorCal were all "open access". You could enter and exit them at any place you wished, just like any other lane.

That's the case for many other highways with HOV lanes in NorCal as well.

I imagine the main difference is that most of these "open access" HOV lanes are time-limited; outside of the morning and evening weekday rush hours they're not HOV lanes. It makes more sense to have stronger separation for full-time HOV (or toll) lanes.

He's referring to the people that drive whatever speed they want to in lane #2.

I was under the assumption that HOV lanes cannot be crossed over (double or single white lines) while carpools are dotted and are open to traffic flowing in and out.

Of course you can only use it as an overtake lane in none-carpool hours, but now that’s not even an option.

The California DOT says they are synonymous[1]:

>High-Occupancy Vehicle (HOV) lanes, also known as carpool or diamond lanes

[1] - https://dot.ca.gov/programs/traffic-operations/hov#:~:text=W....

There's no distinction between HOV and carpool; they're just different names for the same thing. Whether or not the lanes are separated with designated entry/exit points or are open-access is a matter of local policy and design for that specific highway.

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