new freeway to freeway meter lights - CA 67 SB to CA 52 WB

[agentsteel53]

they just put these up between yesterday morning's commute and this morning's commute.

I wonder what engineering analysis determined that this is the place for the lights.  as far as I can tell, the major bottlenecks in the morning are 125 NB to 52 WB, and then later down the line, 52 WB to 805 NB.  I've never encountered any sort of a backup, ever, at 67/52.

[The High Plains Traveler]

Maybe they hired someone from Minnesota DOT. Twin Cities area has several of them. My recollection is, they always ran them with a pretty quick cycle, just enough to create a space between incoming cars.

[ARMOURERERIC]

Were you able to see if they had also put up a set on the 52WB mainline under the 125N to 52w flyover?

[agentsteel53]

Were you able to see if they had also put up a set on the 52WB mainline under the 125N to 52w flyover?

I didn't spot any on 52WB mainline.  now that would surely be a silly way of resolving this: making the entire mainline stop for the merging traffic.

[ARMOURERERIC]

But I have seen similar examples in Los Angeles .  Like 105 out of LAX, don't know if they ever use the signals, but they are there.  Think about it, if there was a massive backup on WB 52 down the hill pushing Fanita, would you rather impede 52 or 125?

[roadfro]

Interesting and unusual to put meters on a freeway-to-freeway ramp, but not unprecedented. For this to be a thing though, the backups from this ramp should be a major nightmare at the mainline downstream merge--if that's not the case, I'm not seeing the need. Especially tricky, since you may need a very quick cycle and a long ramp to adequately handle the flows so that meter lines down queue to the upstream exit.

Are the lights temporary? If so, maybe it's in anticipation of some upcoming project...?

[agentsteel53]

I didn't spot any on 52WB mainline.

I made sure to look this morning, and indeed there are none.

the 52/125 is about 3 miles downstream of the 52/67 and is the real bottleneck of the eastern part of the 52 freeway.  (the overall bottleneck, 52/805, is more an 805 issue andi is also ~12 miles to the west.) 

so maybe they are thinking that by metering the 67 traffic as it gets on 52 (52 begins there, so all traffic is from 67NB* or 67SB) they can unhose some of the 125 issues?

* I have not been on 67NB approaching 52 recently, so I don't know if there are metering lights there or not.

[myosh_tino]

Interesting and unusual to put meters on a freeway-to-freeway ramp, but not unprecedented. For this to be a thing though, the backups from this ramp should be a major nightmare at the mainline downstream merge--if that's not the case, I'm not seeing the need. Especially tricky, since you may need a very quick cycle and a long ramp to adequately handle the flows so that meter lines down queue to the upstream exit.

Are the lights temporary? If so, maybe it's in anticipation of some upcoming project...?

Interesting... yes.  Unusual... perhaps but it's becoming more common in California.

The first operating freeway-to-freeway metering light I can remember was on the ramp from south I-680 to north US 101 in San Jose and I seem to recall that light operating as early as the mid-80's.

In a similar setup to what agentsteel53 is seeing at the 67/52 interchange, in 1994, the north 101 ramp to north 85 was metered from day one.  At the same time, almost all of the ramps connecting CA-85 and CA-17 in Los Gatos were also metered.

More recently, functioning freeway-to-freeway metering lights have popped up at the 237/880 interchange in Milpitas (EB 237 to NB 880, early 2000's), 101/237 interchange in Mountain View (EB 237 to SB 101, 2009) and the 92/880 interchange in Hayward (EB 92 to NB 880, 2011).

There are also numerous freeway-to-freeway metering lights installed but not activated with the most recent ones being at the 280/85 interchange in Cupertino (NB 280 to NB/SB 85) and the 280/880 interchange in San Jose (SB 280 to NB 880).

That's all I can recall off of the top of my head.  I'm sure there are plenty of freeway-to-freeway meters in southern California but I'll leave those to someone who lives down there.

[rschen7754]

405 south to 105 east has them, and they are used. There's also one on 56 west to the I-5 truck bypass southbound...

[roadfro]

I had no idea there were that many freeway to freeway ramp meters in California. I guess it makes some sense as a stopgap measure, especially if it's not possible to lengthen ramps or do any other capital improvements to help avoid weaving concerns.

in 1994, the north 101 ramp to north 85 was metered from day one. 

There's really no need for that ramp to be metered, since that ramp is basically the beginning of the 85 freeway in that direction. The only traffic it would be merging into is the traffic on the HOV flyover. That one is really just a waste.

[myosh_tino]

in 1994, the north 101 ramp to north 85 was metered from day one. 

There's really no need for that ramp to be metered, since that ramp is basically the beginning of the 85 freeway in that direction. The only traffic it would be merging into is the traffic on the HOV flyover. That one is really just a waste.

You'd think so and when CA-85 opened in 1994, many drivers felt the same way.  As a result, county officials demanded that meter be turned off.  Caltrans obliged and the impact was immediate and quite staggering.

With the meters on, the drive from the 101/85 interchange in San Jose to Mountain View took 33 minutes which included the time spent waiting behind the metering lights.  When the 101 to 85 meter was turned off, that same drive took 45 minutes due to increased congestion.

Within a few weeks, the 101 to 85 metering lights were turned back on and have been on ever since.

[roadfro]

I'm just having trouble imagining that the ramp that begins a freeway would have that much of an effect, since it's effectively the beginning of the freeway mainline and ramp meters are supposed to regulate traffic merging into the mainline.

[hm insulators]

405 south to 105 east has them, and they are used. There's also one on 56 west to the I-5 truck bypass southbound...

Aren't there also some from the 405 to eastbound I-10?

I know they have them at the end of the 2 Freeway merging onto westbound I-210.

[mrsman]

in 1994, the north 101 ramp to north 85 was metered from day one. 

There's really no need for that ramp to be metered, since that ramp is basically the beginning of the 85 freeway in that direction. The only traffic it would be merging into is the traffic on the HOV flyover. That one is really just a waste.

You'd think so and when CA-85 opened in 1994, many drivers felt the same way.  As a result, county officials demanded that meter be turned off.  Caltrans obliged and the impact was immediate and quite staggering.

With the meters on, the drive from the 101/85 interchange in San Jose to Mountain View took 33 minutes which included the time spent waiting behind the metering lights.  When the 101 to 85 meter was turned off, that same drive took 45 minutes due to increased congestion.

Within a few weeks, the 101 to 85 metering lights were turned back on and have been on ever since.

That's really interesting.  Can anyone (maybe a traffic engineer) explain why this is the case? I would assume that metering lights are used to reduce mainline backup by shifting the backup to the onramps.  Yet here, the on-ramp is the mainline since this is the start of the freeway.

405 south to 105 east has them, and they are used. There's also one on 56 west to the I-5 truck bypass southbound...

Aren't there also some from the 405 to eastbound I-10?

I know they have them at the end of the 2 Freeway merging onto westbound I-210.

105 was the first freeway to have them and I remember when 105 opened (and I was still living in L.A.) that it was part of  the featured news stories explaining to drivers to be aware of the metering lights when transferring between the 105 and the other freeways.  Even though ramp metering was very common in Southern California, this was the first time we've ever seen ramp metering on freeway to freeway or any type of freeway exit.  IIRC there are meters between 105 and all freeways it interchanges with: 405, 110, 710, and 605, but I'm not sure if every ramp is controlled by a meter.

Once these were shown to be successful, they expanded the freeway to freeway meter ramps to other interchanges as well, such as the above mentioned 10/405 and 210/2.