One car per green: Why the lights on freeway onramps can’t end traffic jams | Hacker News Reader

One car per green: Why the lights on freeway onramps can’t end traffic jams

latimes.com

21 pointsPaulHoule23 comments

Everyone knows that the only way to solve freeway traffic is to add another lane of traffic \s.

This feels a bit pointless and a waste of resources. Increasing the average speed of cars by 1 or 2 MPH doesn’t help anybody.

2 MPH over 10 is 20%. I've done worse things to a system to get a 20% bump in throughput.

It's funny, in a "Soviet Russia lines-up-you" kind of way. When you give valuable things away for free, you get lines.

But I don't think even GDR got as far as installing traffic lights to control a queue to get into a queue. A queue^2 as it were. With back-pressure on the back-pressure! I wonder if they ever see resonance on the back-pressure-back-pressure control system for the queue-queue?

> You’ve probably noticed a fair number of left-turn signals on city streets that remain steadfastly red until a car or two lines up in the left-turn lane. That’s because the lights are controlled by a computer, which is triggered by sensors under the pavement in the turning lane.

Wow, I'm sure people who run red lights feel vindicated when they learn of dehumanizing shit like this.

How did you come to such a drastic opinion about on-demand traffic lights? What makes them "dehumanizing shit" in your opinion?

In other words: Why would you regularly hinder main traffic to allow a left turn if no one is there to make the turn most of the time?

Because on Van Nuys Blvd the sensors are vandalized regularly, especially around the court house at Erwin, and further North near Panorama City, and you will sit at those left turn lights late in the evening for a very long time, yet no cars pass by. And there are other places like that too. Venice Blvd just west of Lincoln, in the two decades I've lived in L.A., the left turn lights in that area are so badly programmed they might as well not exist. There will be eight or nine cars backed up at Venice & Overland, and they will briefly blip green enough for a car or two to get through, yet the left turn light at Glendon will sit on green long after the last car has passed through. There's a reason people shortcut down Glendon, then jink on to Overland further down at a T-junction with a functioning set of lights. Same problem exists on Fairfax around the school and theatre. You get to know precisely which lane you should sit in for which section of the road, that literally varies block to block, because the left turn lights will block up traffic all the way back to Canter's deli all the way from Santa Monica if it is the wrong time of day.

Induction sensors are being phased out for cameras which I have observed do a much better job. For example magnetic sensors will “shut off” the lane if there’s too much space between turning cars, camera systems on the other hand allows for all the waiting vehicles to turn before shutting off.

> Why would you regularly hinder main traffic to allow a left turn if no one is there to make the turn most of the time?

Because it doesn't account for sensor failures. They routinely fail to detect motorcycles and would certainly neglect bicycles, so much so that the subject is addressed in the MSF course and they sell magnets and other bolt-on crap to try to increase chances of triggering them.

Most states (or at least any that I've ridden in) have laws on the books that allows motorcycles to run a red light if a full cycle occurs without them getting a turn.

Sensor failures are accounted for.

ex: https://www.abatemn.org/legislation/mn-laws-regs/mn-red-ligh...

Not the OP but I’ve had situations of waiting at a weight-sensor-triggered left turn light for so long that I had to back up and turn right then u-turn.

Los Angeles, mid-sized sedan.

FYI, they're usually not weight sensors, but instead they are triggered by a current momentarily induced by a large hunk of steel moving over top of them. If you find yourself in this situation in the future, you can try reversing and pulling up in a slightly different lane position. (preferably by braking harder, so as to increase your velocity over the sensor and the magnitude of the current induced.) Look for hexagonal cutouts in the asphalt and attempt to drive directly over them.

Thank you for this. Yes there are visible round cutouts in the concrete. So basically roll back and forth over them until the light changes?

Yep, the faster the better. (safely as you can, of course)

Sure, but you don't run red lights, we can charitably presume.

Yes we can :)

The only time I've gotten a ticket of any kind in 30 years of driving a car is because of a left turn light on an empty highway that steadfastly refused to turn green. Pulled up, waited, waited, waited, through multiple cycles of green in the other directions. No cars passed by. Ever. Finally, after five or six cycles, and at least eight minutes of time I went "f** it" and made the left turn, with no vehicles in sight in either direction for the entire time I sat at that light in the middle of nowhere. And then a cop car tucked away on the side of the road lit up like a Christmas tree. He knew. Taking a nap, and making quota I am sure of it.

I would absolutely fight that ticket. Most states have provisions in the law for a malfunctioning signal.

Name and shame the location?

Happens everywhere these days depending on your car, or god forbid scooter.

In Utah all left turns are unprotected, way more efficient. Similar to how intersections without traffic lights have been proven to be more efficient.

The biggest issue is that out of state drivers don’t learn these skills, so we frequently get people with CA plates that don’t know how to pull into the middle of an intersection and that it’s legal to run a red during a light change, and the system breaks down

You are downvoted, but have a point. One of my smallest cars and my motorcycles fail to trigger these so often, there is literally a law that allows me to run the red after a few minutes of waiting in most states.

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