Traffic lights in Portland metro area (Beaverton, Beaver: transporting, law, dangerous)

[KJoe11]

Hi.

First, I want to flatly state I am not very knowledgeable in traffic patterns and traffic light technology. However...
IMHO, I find traffics lights in the Portland area a bit dysfunctional. Does any know why:

1 - Most areas don't appear to have the traffics lights timed in order to keep the flow of traffic moving.
2- When traffic goes yellow to red. The cross sections immediately get a green light. It seems a bit dangerous
3- Why does the left turn lane arrow remain red for some seconds while the rest of lanes are green before turning yellow?

Anyone know these questions, please let us know.

Thanks in advance

[Sherwoody]

You can ask them directly by sending an email to askodot@odot.state.or.us or call 1-888-275-6368. If you are specific as to the light location, they will tell you exactly why it is set they way it is.

[jjpop]

Originally Posted by KJoe11

3- Why does the left turn lane arrow remain red for some seconds while the rest of lanes are green before turning yellow?

My guess on this one is so that left-turners don't presume they can make their turn as soon as they see the light change and crash into the oncoming traffic. By delaying the change, the oncoming traffic has a chance to fill the intersection before the left-turners advance.

[Steve Pickering]

Unplanned traffic patterns of the past without a way to fix in the present. ...........

[bler144]

Originally Posted by jjpop

My guess on this one is so that left-turners don't presume they can make their turn as soon as they see the light change and crash into the oncoming traffic. By delaying the change, the oncoming traffic has a chance to fill the intersection before the left-turners advance.

In Pittsburgh that's an accepted practice, and apparently is even named the 'Pittsburgh Left.' (with its own wiki page: http://en.wikipedia.org/wiki/Pittsburgh_left) All participants expect it to happen and accommodate it.

But I think you're right, that seems to be exactly the intent. It seems most common in places where the left turn would be across multiple lanes of oncoming traffic, and where someone trying to jump out likely would interfere with those lanes progressing normally.

I'm assuming the OP moved from the east or upper-midwest, where a 1 sec delay between red/green is normal in many states. The downside of this is that the becomes general practice for drivers to adapt and stretch the yellow because they know they have an additional buffer. It's functionally no better/worse, just different.

In Oregon the law requires that you stop for a yellow if it is safe to do so, thus if you drive like you would in Chicago (where everyone expects that you won't stop), you're likely to end up with a ticket. In my mind the issue isn't the lack of delay between red/green, it's that 4 sec seems to be the standard yellow length regardless of the speed zone or length of the intersection. In some places the engineering seems to create 'sour spots' where you're forced to slam your brakes, or still be out in the intersection when the cross-traffic has a green light. Thus potentially getting a ticket even if you can argue it wasn't safe to stop - the courts seem to back the police on ticketing it anyway.

Though I do see a lot of people still clearly violating the law and running the red, as well.

[Steve Pickering]

In Arizona if you are beyond a line that extends from the start of the sidewalk arc curve midpoint on the corner extending to a point on the opposite corner, you have the right of way even if the light is red. Otherwise you are guilty of running the light.

[Leisesturm]

Originally Posted by KJoe11

2- When traffic goes yellow to red. The cross sections immediately get a green light. It seems a bit dangerous

This is the only point of your post that I agree with. Yes, it seems a bit dangerrous, and NYC for one, has had all the lights turn red for a beat to clear the intersection before allowing the standing traffic to proceed. Oregon's way works only if you are a car. A cyclist or pedestrian caught out by a stale yellow is at the mercy of the judgment of standing traffic. Worse, there will be drivers heading towards the intersection at speed who have anticipated the light change and therefore have no plan to stop. When the cyclist or ped fails to clear the intersection in the alloted time... boom... and it will be a boom, because they will have been hit by a car traveling at fairly high speed. I think the reason such accidents don't happen more often is because cyclists in particular, have learned to avoid such situations like the plague. I haven't. Several times I have just squeaked past a low flying crew-cab who, if he had nailed me, would have been fully justified in doing so. But I didn't run any red light, I was simply crossing an intersection that has lights timed for a car traveling 25mph that can get through that intersection in half the time that it takes a cyclist to do it. Pedestrians have countdown timers that they can trigger, but cyclists have nothing, unless they drag their bike up onto the sidewalk and trigger the pedestrian crossing.

As to the other points you raised. 1. I primarily ride in the suburbs, lights are indeed timed to keep traffic moving. In town, I suspect that there are a few routes where the lights are "synchronized", but that there will be several that appear not to have any pattern. That is intentional. The intent was too keep drivers from anticipating the time-out of their light and tailgate the car ahead of them through the intersection. Mostly it fails because drivers are... drivers. There isn't anything traffic planners can come up with that drivers won't try to defeat. I also don't know about where you drive, but where I ride, the traffic signals all respond to the presence of traffic over sensors in the roadbed. When left turning traffic on the far side of the intersection has a green arrow, left turning traffic on the other side will be held by a red arrow until the last car in the queue makes it through the intersection OR a pre-determined time-out interval is exceeded.

But... why worry about it? This is like the fourth thread on traffic in Portland in this week. When I arrived in Portland I soon realized that traffic and traffic signals operate differently from where I was from. Instead of getting upset I studied the patterns. I now understand them pretty well. As Steve said, although he was being snarky about it: traffic is here to stay. The roads were never designed for the volume of traffic they have to manage. And never will be. Ever. It is simply impossible to re-engineer the roads to handle the increase in population. Impossible. Completely. Drivers must adapt and/or change their expectations of ETA or average speed. Cars must get smaller. Much, much, much smaller, and, finally a portion of the driving public must find alternate means of commuting, and generally transporting themselves around the region.

H

[bler144]

Originally Posted by Leisesturm

As to the other points you raised. 1. I primarily ride in the suburbs, lights are indeed timed to keep traffic moving. In town, I suspect that there are a few routes where the lights are "synchronized",

Agreed overall. Worth noting that some traffic lights will appear to be non-synched just because they aren't synched for your particular path.

Case in point would be somewhere like Cornell road through Beaverton. It's synched pretty well for 1 direction (east bound? I can't recall. But if you're going 5 mph over the limit you'll make every yellow light for quite a ways) but going in the other direction it isn't at all. Same is true for stretches of 30-bypass.

The math often just doesn't work for it to accomplish synch in all directions (and it's even worse once you're factoring in traffic turning left), so engys/planners have to decide which synch provides the most benefit.

[hamellr]

Originally Posted by KJoe11

1 - Most areas don't appear to have the traffics lights timed in order to keep the flow of traffic moving.

A major part of this is a combination of jurisdictions over who owns the traffic lights on certain roads and traffic engineers who have not worked together to fix issues across those jurisdictional borders. You also have to factor in that certain routes will have higher priority as major through fares for Emergency Vehicles.

On the other hand, it's also a commonly accepted tactic to encourage people to not drive and take alternative methods of travel.

It's actually a very complicated science and very easy for us to say "just time the lights the same and be done with it." But we don't really understand how doing something like that can easily impact traffic across an entire city.

[urbanlife78]

Originally Posted by KJoe11

Hi.

First, I want to flatly state I am not very knowledgeable in traffic patterns and traffic light technology. However...
IMHO, I find traffics lights in the Portland area a bit dysfunctional. Does any know why:

1 - Most areas don't appear to have the traffics lights timed in order to keep the flow of traffic moving.
2- When traffic goes yellow to red. The cross sections immediately get a green light. It seems a bit dangerous
3- Why does the left turn lane arrow remain red for some seconds while the rest of lanes are green before turning yellow?

Anyone know these questions, please let us know.

Thanks in advance

Depends on where you are, in downtown the lights are all timed, the rest of the city of Portland does time their lights, though not all of them work together. Outside of the city, it can vary from area to area.

The light changes, the reason why there isn't a delay is because their isn't a problem with it. Oregon drivers tend to be more defensive drivers and less aggressive than northeast American drivers. You don't have to worry about people flying through lights after they turned red in Oregon and most people their begin to break when they see yellow.

Not sure what you are asking for the third point. From how I am taking the question, I would say so that it prevents people from trying to run a yellow and turn too hard because if you are running a yellow on a turn, you know that opposite traffic won't be coming immediately.