What do you think constitutes "perfect" signal timing?
In my opinion cars should miss the first light after they turn onto a main road. They wait at the next red while thru traffic approaches. Then they become part of the thru traffic, and are in sync to make all green lights thereafter. Obviously this is in a perfect world, and may not be achievable for any number of other factors.
Michigan does it pretty well, as do the one-way avenues in New York City. It doesn't exist where I live.
And yes, the first light should be missed; it's green for people going straight, not people coming from a turn.
A mythological creature, akin to a unicorn or dragon. Much like the other two, it cannot be found in Oklahoma.
Extinct in most of Illinois (downtown Ottawa has it), it is fairly common in most of Michigan.
Examples:
Oh man, I wish NJ 73 had signal timing like that. It would truly shave 10-15 minutes from my commute, and I would never need to use I-295 instead.
Here is a time-distance for Woodward Avenue in Detroit:
(https://i.imgur.com/bvb8y20.jpg)
Achieving good signal progression in both directions of travel along a 2-way road comes down to three main variables.... signal spacing, cycle length, and speed. The posted speed of Woodward is 45 mph and the signals are spaced roughly 3,000 feet apart. If the speed and signal spacing along a corridor stays consistent you can figure out the cycle length that will achieve good signal progression in both directions. I put together a chart that figures out the resonant cycles for different speeds and signal spacing. In the case of Woodward the signals need to run roughly 90 seconds to achieve good signal progression in both directions of travel (the corridor is actually timed for about 48 mph, but most people are going a few miles over the speed limit anyways so it works out well).
(https://i.imgur.com/xYvv6GI.jpg)
Quote from: Brandon on October 31, 2017, 10:10:30 AM
Extinct in most of Illinois (downtown Ottawa has it), it is fairly common in most of Michigan.
Does North Avenue no longer have it out in the western 'burbs?
Quote from: kphoger on October 31, 2017, 11:37:47 AM
Quote from: Brandon on October 31, 2017, 10:10:30 AM
Extinct in most of Illinois (downtown Ottawa has it), it is fairly common in most of Michigan.
Does North Avenue no longer have it out in the western 'burbs?
No, not since North Avenue was rebuilt a few years ago. Too many dual left turns along it from IL-59 east to IL-83. Sad, IDOT had a chance to emulate MDOT (see the videos above) and blew it.
Quote from: bzakharin on October 31, 2017, 10:16:54 AM
Oh man, I wish NJ 73 had signal timing like that. It would truly shave 10-15 minutes from my commute, and I would never need to use I-295 instead.
Hurting NJ 73 (and most NJ roads) is the jughandles. It would be fine if every intersection has jughandles, or every intersection has left turn lanes. But when there's a combination of the 2, it's impossible to have the cycle lengths consistent. At intersections such as 73 and Church Road, extra time needs to be devoted to the cross streets, which takes away time from 73. An eventual overpass will solve some of that problem, but that's years down the road...
Quote from: Scott5114 on October 31, 2017, 08:07:08 AM
A mythological creature, akin to a unicorn or dragon. Much like the other two, it cannot be found in Oklahoma.
Ugh. Tulsa has signal un-timing down to a fine art. Not only do the vast majority of them work independently, there are places where it looks like a traffic signal salesman came through and made them a deal.
Yale avenue between 61st and 71st Streets: Signals at 61st, St. Francis Hospital entrance, 65th, 66th, 68th, and 71st Streets. All operate independently of the others. :pan:
41st Street between Yale Avenue and Sheridan Road: Signals at Yale, Darlington, Hudson, I-44 frontage roads, and Sheridan. Again, all operate independently and cause tremendous backups along this stretch. Oh, and this is the "improved" setup following the rebuilding of I-44 a few years ago. :banghead:
Apologies for a bit of topic creep, but the subject is a big sore spot with me, living here in the land progress forgot.
IMO, there are 3 main reasons why most roads are incapable of good dual signal progression.
#1. Irregularly spaced traffic signals: If the signal spacing between traffic signals is constantly changing along the corridor, then the cycle length that achieves perfect dual progression is constantly changing too. If a set of lights has a perfect dual progression at a 90 second cycle, but the next set of lights has a perfect dual progression at 130 second cycle, what cycle do you time the corridor for? Either you compromise and pick the cycle length that works best for the entire corridor or you break it up where some of the signals run different cycles altogether.
#2. Signals are too closely spaced: The most obvious example of this would be a two-way street in Manhattan like Broadway. While the traffic signals are evenly spaced, they are only 260 feet apart. Anybody driving Broadway intuitively knows that getting a string of green lights in both directions is impossible. As speed of the corridor increase, the distance between traffic signals also must increase to be able to maintain dual progression. The Woodward signals are spaced about 3000 feet apart and the speed limit is 45 mph. Even along a Michigan left corridor that eliminate the need for left turn phases, the 90 second cycle just barely fits along Woodward. If the signals were spaced any closer (or the speed limit was set any higher), the dual signal progression would be lost.
#3. Pedestrian crossings are too long: A side-street pedestrian crossing of 150 feet would need to run 52 seconds to adhere to the MUTCD and safely fit the pedestrians (there are literally dozens of major Orlando intersections with side-street crossings this long). In general you want your main-street to run just as long, if not longer, than your side-street. Assuming the main street also runs 52 seconds, the cycle length is up to 104 seconds. But we haven't accounted for left turn phases yet. Add 20 seconds for both left turn phases and the cycle length is creeping up to 150 seconds. Maybe a corridor in Orlando would achieve perfect dual progression at 100 seconds, but since the pedestrian crossing distances are so long it really can't run that short of a cycle. Technically you can use pushbuttons and only run the side-street the full 52 seconds when the pushbutton is pressed, but then the signal will get out of step with the surrounding signals every time a pushbutton is actuated.
Quote from: jeffandnicole on October 31, 2017, 12:20:47 PM
Quote from: bzakharin on October 31, 2017, 10:16:54 AM
Oh man, I wish NJ 73 had signal timing like that. It would truly shave 10-15 minutes from my commute, and I would never need to use I-295 instead.
Hurting NJ 73 (and most NJ roads) is the jughandles. It would be fine if every intersection has jughandles, or every intersection has left turn lanes. But when there's a combination of the 2, it's impossible to have the cycle lengths consistent. At intersections such as 73 and Church Road, extra time needs to be devoted to the cross streets, which takes away time from 73. An eventual overpass will solve some of that problem, but that's years down the road...
Why do they do that anyway? How do they decide on jughandle vs regular intersection?
Quote from: tradephoric on October 31, 2017, 11:26:49 AM
Here is a time-distance for Woodward Avenue in Detroit:
(https://i.imgur.com/bvb8y20.jpg)
I don't think any of us has any clue how to read this graph. I've seen several of them posted without comment from others, which I think is because none of us know what we're looking at here. It's like reading a weather balloon sounding if you've never done such.
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fwww.greenskychaser.com%2Fblog%2Fwp-content%2Fuploads%2F2011%2F05%2FOUN.gif&hash=301e9dd11f68c25fc8081d88ccd7054c3b1ae631)
Quote from: tradephoric on October 31, 2017, 02:11:22 PM
IMO, there are 3 main reasons why most roads are incapable of good dual signal progression.
You missed the biggest (and most common) reason:
#0. The controlling agency shows no motivation toward achieving good signal progression. Signal progression doesn't magically happen on its own; the agency must actively work toward it. If there's no buy-in from the agency, you won't have interconnected signals and you won't have any attempt to space the signals to work toward it. Even if the road is otherwise a perfect candidate for good signal progression, someone has to be assigned to come up with the timings and program them into the controllers. That doesn't happen unless the higher-ups make it happen.
You could get a decent signal progression going along State Highway 9 in Norman, Oklahoma, but neither ODOT nor the City of Norman (not sure who's responsible for the signals) are inclined to make it happen. So we all suffer in traffic.
^ I learned about those graphs in school last semester. The x axis is time, while the y axis is distance along the road. Green, yellow, red are the phases for each intersection on the road. The blue lines represent southbound cars, while the red lines represent northbound cars. Basically, each blue and red line represents the movement of a car along the road. If it passes through a green, then the line will continue straight. If the line hits a red light, it will go to the right until the green phase begins (which represents waiting for the signal). Since this example shows most of the lines (cars) passing through multiple greens without stopping, it shows that the signal progression is good.
I will agree that many major thoroughfares in Michigan have timing down pretty well (until traffic volumes increase so much that the roads can't handle it in general). Many roads also have "smart" traffic lights that monitor the traffic flow and adjust the timing.
But in smaller towns and suburbs, sometimes they set the lights so you have to stop for most of them, as "calming". Until you realize that if you go about 10 or 15 mph over the limit, you make the lights!
Quote from: Scott5114 on October 31, 2017, 06:36:11 PM
You missed the biggest (and most common) reason:
#0. The controlling agency shows no motivation toward achieving good signal progression. Signal progression doesn't magically happen on its own; the agency must actively work toward it. If there's no buy-in from the agency, you won't have interconnected signals and you won't have any attempt to space the signals to work toward it. Even if the road is otherwise a perfect candidate for good signal progression, someone has to be assigned to come up with the timings and program them into the controllers. That doesn't happen unless the higher-ups make it happen.
There can always be improvements with signal timings along a corridor, but ultimately the geometry of the roadway dictates how well a corridor can be timed. When you get to the situation where you have 7 traffic signals along a 1 mile stretch of road, throwing any timing into the signals will work almost as well as a totally optimized timing (since the optimized timing will still stop a lot of cars at red lights simply due to how closely the traffic signals are spaced.. and how many there are).
Quote from: Scott5114 on October 31, 2017, 06:36:11 PM
You could get a decent signal progression going along State Highway 9 in Norman, Oklahoma, but neither ODOT nor the City of Norman (not sure who's responsible for the signals) are inclined to make it happen. So we all suffer in traffic.
The spacing of the signals on State Highway 9 east of I-35 isn't great. The signals aren't evenly spaced and they are spaced too closely together. You could get good progression in one direction, but the other direction will suffer. The problem is cities don't care how a proposed traffic signal will affect signal progression along major corridors. They just want the tax base of major developments in their city. If a strip mall warrants a traffic signal at the entrance, they'll just put it in even if there are already several other traffic signals in the surrounding area. What you get is drivers stopping at every other red light. And in reality there aren't that many traffic signals along State Highway 9, but there are enough to screw up progression. I wouldn't be surprised if you get stopped at McGee Drive often and that's the light you curse out the most.
I mentioned this in the "single ideas" thread, but if you can't time it for both directions, what about timing traffic lights in one direction, and then in the other direction for a parallel or near-parallel road?
The example I used was MA 114 and MA 62 between I-95 and MA 128, but I don't think most people are familiar with those roads.
Lightly traveled side streets on main thoroughfares with lights that only trigger if someone pulls up on the side street are a good idea EXCEPT for folks on the main thoroughfare who turn off onto the lightly traveled side street and swing wide making the turn and thus tripping the lights for NOBODY.
You dirty bastards !!!
I hate you I hate you I hate you !!! I want to hurt you, and keep on hurting you. From hell's black depths I will expend my last breath HATING you !!!
:no:
Quote from: Jardine on November 01, 2017, 11:46:24 AM
Lightly traveled side streets on main thoroughfares with lights that only trigger if someone pulls up on the side street are a good idea EXCEPT for folks on the main thoroughfare who turn off onto the lightly traveled side street and swing wide making the turn and thus tripping the lights for NOBODY.
You dirty bastards !!!
I hate you I hate you I hate you !!! I want to hurt you, and keep on hurting you. From hell's black depths I will expend my last breath HATING you !!!
:no:
LOL tell us how you really feel! They can put a few second delay on the detector so the call doesn't go to the controller until someone is physically stopped over the detector for a few seconds. This is usually enough to solve the problem of a wide swinging vehicle from tripping the detector.
Quote from: tradephoric on November 01, 2017, 11:33:37 AM
I wouldn't be surprised if you get stopped at McGee Drive often and that's the light you curse out the most.
Imhoff, Chautauqua, and Jenkins tend to be the worst offenders in my memory. I tend to be going westbound during periods of heavy traffic; when I come back eastbound it's late enough that the signals are all camera-actuated.
Quote from: 1 on November 01, 2017, 11:45:20 AM
I mentioned this in the "single ideas" thread, but if you can't time it for both directions, what about timing traffic lights in one direction, and then in the other direction for a parallel or near-parallel road?
The example I used was MA 114 and MA 62 between I-95 and MA 128, but I don't think most people are familiar with those roads.
I wish this would be implemented. In Los Angeles, there was a plan about 10 years ago that was floated to make two wide streets, Olympic and Pico, each one-way in order to improve traffic. One-way traffic could implement progression, utilize the existing left turn lane for driving, and be generally more efficient. This was shot down because it was thought to lead to speeding, it would complicate transit along those routes, and the routes were too far apart from each other (typical one-way pairs are about 1 block apart, these distance between these two streets being about 1/4 -1/2 mile at times).
But if they instead kept both streets two-way but had the progression of each street differ, this would have made a great impact. In this part of LA, traffic is about equal eastbound and westbound at rush hour. In fact, traffic is usually worse heading away from Downtown in the mornings. But this was never implememnted.
Another good candidate: Adams/Washington near the 10 freeway from Culver City to Downtown.
Quote from: GaryV on October 31, 2017, 06:54:33 PM
I will agree that many major thoroughfares in Michigan have timing down pretty well (until traffic volumes increase so much that the roads can't handle it in general). Many roads also have "smart" traffic lights that monitor the traffic flow and adjust the timing.
But in smaller towns and suburbs, sometimes they set the lights so you have to stop for most of them, as "calming". Until you realize that if you go about 10 or 15 mph over the limit, you make the lights!
In Metro Detroit, I'm familiar with this phenomenon working on Woodward and on Telegraph, as I've seen videos for drivers along both streets cruising along. Does it work on most other N/S streets? The E/W streets?
Plus some places just don't want coordinated signals. Saratoga Springs bought an expensive signal timing system a few years ago and scrapped it after business complained about people not stopping in front of their stores any more. And there's a light I pass by every single day that I swear only exists for "traffic calming" purposes.
Quote from: vdeane on November 01, 2017, 08:20:45 PM
Plus some places just don't want coordinated signals. Saratoga Springs bought an expensive signal timing system a few years ago and scrapped it after business complained about people not stopping in front of their stores any more. And there's a light I pass by every single day that I swear only exists for "traffic calming" purposes.
I remember and am still waiting for the coordinated system on Central Ave that was touted by John Poorman at CDTC. He used to boast that you would be able to drive between Albany and Schenectady without stopping and it would be the most innovative project in the country (used to joke that he loved The Jetsons way, way too much; pie-in-the-sky is an underestimated description of his "visions").
Every time the Waterman Ave light stops Central Ave traffic to let one car turn left, I think of him and laugh.
The mission statement of the National Association of City Transportation Officials (NACTO) is to build cities as places for people, with safe, sustainable, accessible and equitable transportation choices that support a strong economy and vibrant quality of life. They put together an interesting website that talks all about signal cycle lengths and how they affect pedestrians. Here is a snippet:
QuoteThough often invisible to the public, traffic signal cycle lengths have a significant impact on the quality of the urban realm and consequently, the opportunities for bicyclists, pedestrians, and transit vehicles to operate safely along a corridor.
Long signal cycles, compounded over multiple intersections, can make crossing a street or walking even a short distance prohibitive and frustrating. This discourages walking altogether, and makes streets into barriers that separate destinations, rather than arteries that stitch them together.
https://nacto.org/publication/urban-street-design-guide/intersection-design-elements/traffic-signals/signal-cycle-lengths/
NACTO is promoting short cycle lengths of 60-90 seconds so that pedestrians can cross the street without waiting too long. But along major suburban corridors you see cycle lengths double that of 120-180 seconds, especially during rush hour. Regardless of how cycle lengths affect pedestrians, I believe shorter cycles can push more traffic through a signal than longer cycles. That goes against conventional wisdom, as short cycle lengths increased the % of lost time at the signal (ie. yellow and all red times soak up more of the pie). But with longer cycles, the saturation flow rates reduces as the phase time increases. Previous research that has been done on cycle lengths suggests a 45 second phase time optimizes the throughput of a saturated phase. After 45 seconds, traffic begins to spread out and not utilize the green time anyways. So for a 2-phase intersection, a 90 second cycle would theoretically be the optimal cycle length (which is what Woodward Avenue runs 24/7).
Since Woodward runs a pedestrian friendly cycle length that optimizes throughput, could it be considered the "perfect" suburban corridor? Well not so fast. Here is another snippet from the NACTO website:
QuoteWhile short cycle lengths are desirable, ensure that cycle lengths are long enough for pedestrians to cross wide streets in a single leg without getting stuck in the median, unless the median is a destination in and of itself.
The problem is pedestrians crossing Woodward get stuck in the median. If you re-time the lights so they could make it all the way across, the cycle length would balloon to about 180 seconds. But now pedestrians who don't want to wait long to get a Walk are waiting at a signal with a 180 second cycle length... Houston, we have a problem.
Quote from: tradephoric on November 02, 2017, 01:04:25 PM
QuoteWhile short cycle lengths are desirable, ensure that cycle lengths are long enough for pedestrians to cross wide streets in a single leg without getting stuck in the median, unless the median is a destination in and of itself.
The problem is pedestrians crossing Woodward get stuck in the median. If you re-time the lights so they could make it all the way across, the cycle length would balloon to about 180 seconds. But now pedestrians who don't want to wait long to get a Walk are waiting at a signal with a 180 second cycle length... Houston, we have a problem.
The solution to this is to make the median a destination. Widen out the median and construct some buildings in the middle. It's called a Town Center Intersection (TCI) and unlike a Median U-turn you don't have to take a turnaround to complete your left turn. It's just simple and effective. Also, in many cases the pedestrian crossings are left to the outside of the box, so in theory pedestrians shouldn't conflict with left turning vehicles (which can be a dangerous vehicle/pedestrian conflicts at an intersection).
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fblog.innovativeintersections.org%2Fwp-content%2Fuploads%2F2017%2F02%2Fimage021.jpg&hash=ca9f65bca34529d1d4299f8d21da2dd2c3669079)
https://www.youtube.com/watch?v=rCQn89wItTY
Here are 3 SYCHRO models of a conventional intersection, Median U-turn, and Town Center Intersection. Each has the same traffic volumes and upstream geometry (two intersecting 6-lane roads). Backups abound at the conventional intersection with protected left turn phases (even with dual left turn lanes). A 4-phase intersection will never have the same capacity as a simple 2-phase intersection.
https://www.youtube.com/watch?v=dZC0VeWo8IY
https://www.youtube.com/watch?v=6Z1NhXYLq9Y
https://www.youtube.com/watch?v=RWIHiNKJ26c
Quote from: tradephoric on November 02, 2017, 02:13:12 PM
The solution to this is to make the median a destination. Widen out the median and construct some buildings in the middle. It's called a Town Center Intersection (TCI) and unlike a Median U-turn you don't have to take a turnaround to complete your left turn. It's just simple and effective. Also, in many cases the pedestrian crossings are left to the outside of the box, so in theory pedestrians shouldn't conflict with left turning vehicles (which can be a dangerous vehicle/pedestrian conflicts at an intersection).
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fblog.innovativeintersections.org%2Fwp-content%2Fuploads%2F2017%2F02%2Fimage021.jpg&hash=ca9f65bca34529d1d4299f8d21da2dd2c3669079)
https://www.youtube.com/watch?v=rCQn89wItTY
In a sense, these town center intersections are like the intersection of 2 one-way pairs.
Here is an example in Laurel, MD of an intersection of two relatively important highways, US 1 and MD-198. Each road expands to one-way pairs for the intersection, as well as for several blocks thereafter. This scenario is far more efficient than a standard intersection with left turn arrows and the like. If you zoom in, you will see special channelization for some of the turns between the one-way segments.
https://www.google.com/maps/place/Laurel,+MD/@39.101069,-76.8508037,15z/data=!4m5!3m4!1s0x89b7dd10e849dcd1:0x98cd5e2efdcd92fc!8m2!3d39.0992752!4d-76.8483061
Quote from: tradephoric on October 31, 2017, 11:26:49 AM
Achieving good signal progression in both directions of travel along a 2-way road comes down to three main variables…. signal spacing, cycle length, and speed. The posted speed of Woodward is 45 mph and the signals are spaced roughly 3,000 feet apart. If the speed and signal spacing along a corridor stays consistent you can figure out the cycle length that will achieve good signal progression in both directions. I put together a chart that figures out the resonant cycles for different speeds and signal spacing. In the case of Woodward the signals need to run roughly 90 seconds to achieve good signal progression in both directions of travel (the corridor is actually timed for about 48 mph, but most people are going a few miles over the speed limit anyways so it works out well).
(https://i.imgur.com/xYvv6GI.jpg)
Quote
IMO, there are 3 main reasons why most roads are incapable of good dual signal progression.
#1. Irregularly spaced traffic signals: If the signal spacing between traffic signals is constantly changing along the corridor, then the cycle length that achieves perfect dual progression is constantly changing too. If a set of lights has a perfect dual progression at a 90 second cycle, but the next set of lights has a perfect dual progression at 130 second cycle, what cycle do you time the corridor for? Either you compromise and pick the cycle length that works best for the entire corridor or you break it up where some of the signals run different cycles altogether.
#2. Signals are too closely spaced: The most obvious example of this would be a two-way street in Manhattan like Broadway. While the traffic signals are evenly spaced, they are only 260 feet apart. Anybody driving Broadway intuitively knows that getting a string of green lights in both directions is impossible. As speed of the corridor increase, the distance between traffic signals also must increase to be able to maintain dual progression. The Woodward signals are spaced about 3000 feet apart and the speed limit is 45 mph. Even along a Michigan left corridor that eliminate the need for left turn phases, the 90 second cycle just barely fits along Woodward. If the signals were spaced any closer (or the speed limit was set any higher), the dual signal progression would be lost.
#3. Pedestrian crossings are too long: A side-street pedestrian crossing of 150 feet would need to run 52 seconds to adhere to the MUTCD and safely fit the pedestrians (there are literally dozens of major Orlando intersections with side-street crossings this long). In general you want your main-street to run just as long, if not longer, than your side-street. Assuming the main street also runs 52 seconds, the cycle length is up to 104 seconds. But we haven’t accounted for left turn phases yet. Add 20 seconds for both left turn phases and the cycle length is creeping up to 150 seconds. Maybe a corridor in Orlando would achieve perfect dual progression at 100 seconds, but since the pedestrian crossing distances are so long it really can’t run that short of a cycle. Technically you can use pushbuttons and only run the side-street the full 52 seconds when the pushbutton is pressed, but then the signal will get out of step with the surrounding signals every time a pushbutton is actuated.
I am so glad to see an in depth discussion of traffic control and engineering on this forum. I wanted to expand a little on what tradephoric said in the above posts:
Conceptually, how can one program traffic signal progression on a 2-way street.
Let's take a simplified example. We have Main Street with a 30 MPH speed (which of course is 1/2 mile per minute). Signals are spaced every 1/4 mile. Signals are set with a 60 second cycle length, meaning 30 seconds for our street and 30 seconds for cross-traffic. [to keep the illustration simple, we will ignore all-red phases, the 30 seconds is the combined green and yellow time.]
You are at the corner of Main & A driving southbound. The first 30 sec of the cycle (00-30) are dedicated to Main, and the second half (30-00) is dedicated to A.
The traffic on Main will reach B Street, 1/4 mile later, 30 seconds later. So to ensure that all of this traffic will still see a green light, the portion of the signal dedicated to Main St traffic at the B street signal must be 30 seconds later than it was at the first signal. I.e. At the Main/B corner, (30-00) is dedicated to Main and (00-30) is dedicated to B.
The traffic on Main will reach C Street, 1/4 mile later, 30 seconds later. So to ensure that all of this traffic will still see a green light, the portion of the signal dedicated to Main St traffic at the C street signal must be 30 seconds later than it was at the second signal. I.e. At the Main/C corner, (00-30) is dedicated to Main and (30-00) is dedicated to C. Note, that this signal keeps the exact same timing as the Main/A signal.
So we have established that southbound Main will progress properly under the scenario. Is it also true for northbound Main? Yes.
You are at the corner of Main & C driving northbound. The first 30 sec of the cycle (00-30) are dedicated to Main, and the second half (30-00) is dedicated to C.
The traffic on Main will reach B Street, 1/4 mile later, 30 seconds later. So to ensure that all of this traffic will still see a green light, the portion of the signal dedicated to Main St traffic at the B street signal must be 30 seconds later than it was at the first signal. I.e. At the Main/B corner, (30-00) is dedicated to Main and (00-30) is dedicated to B.
The traffic on Main will reach A Street, 1/4 mile later, 30 seconds later. So to ensure that all of this traffic will still see a green light, the portion of the signal dedicated to Main St traffic at the A street signal must be 30 seconds later than it was at the second signal. I.e. At the Main/A corner, (00-30) is dedicated to Main and (30-00) is dedicated to A. Note, that this signal keeps the exact same timing as the Main/C signal. Also note that the timing of the signal for both northbound and southbound platoons is simultaneous. Southbound traffic leaving Main/B will reach Main/C at the same time that northbound traffic leaving Main/B reaches Main/A.
So it is imperative that Main/A and Main/C have timing that is equivalent and that Main/B have timing that is
opposite to the timing of Main/A and Main/C. And this is accomplished by making sure that the cycle length of our signals are equal to the amount of time that it will take traffic to traverse the distance between
two signals. Since it takes 60 seconds to travel from A to C at 30 MPH, the cycle length should be 60 seconds to accomplish two-way signal progression.
This knowledge can be applied to derive the following useful formulas for setting the appropriate cycle length:
Cycle Length (sec) = 7.2 X Distance between signals (meters) / Speed (Km/hr)
Cycle Length (sec) = 7200 X Distance between signals (miles) / Speed (MPH)
Cycle Length (sec) = (15/11) X Distance between signals (feet) / Speed (MPH)
The last formula was used to plot the graph above, and you can see that it works. For example, if the distance between signals is 2200 feet and the speed is 30 MPH, the cycle length is 100 seconds. And on the graph, we see that the 30 MPH diagonal intersects the point that is (x=100, y=2200).
Many, many years ago there was decent progression in the Los Angeles area utilizing these formulas. In many parts of the area, especially the San Fernando Valley and Orange County, the main streets were one mile apart. At the half-mile points were important collectors and at the 1/4 and 3/4 mile points were the only other signalized intersections where local streets met the main streets. If signals were kept simple (i.e. no provision for left turns) a citywide progression could be established with a 60 second cylce length at 30 MPH. This was actaully achieved, one of many reasons why the city has historically been averse to installing left turn arrows. Once the left turn arrows came, it became very difficult to fit in every phase within the 60 second cycle and progression was lost.
Quote from: mrsman on November 01, 2017, 08:01:15 PM
Quote from: GaryV on October 31, 2017, 06:54:33 PM
I will agree that many major thoroughfares in Michigan have timing down pretty well (until traffic volumes increase so much that the roads can't handle it in general). Many roads also have "smart" traffic lights that monitor the traffic flow and adjust the timing.
But in smaller towns and suburbs, sometimes they set the lights so you have to stop for most of them, as "calming". Until you realize that if you go about 10 or 15 mph over the limit, you make the lights!
In Metro Detroit, I'm familiar with this phenomenon working on Woodward and on Telegraph, as I've seen videos for drivers along both streets cruising along. Does it work on most other N/S streets? The E/W streets?
Big Beaver / 16 Mile / Metro Parkway (especially the further east you are) is pretty good at it.
Some roads seem to have timing set per rush hour - better timing inbound in the morning, outbound in the afternoon. But since much rush hour traffic is suburb to suburb, there's not as much of a concept of inbound/outbound for many areas. I just know that if you're going the "wrong" way for that time of day, you probably will hit most of the lights red.
I remember years ago along US 31 on the east side of Holland there were even signs stating that the traffic light timing was set for 50 mph. I haven't been there for several years.
(https://i.imgur.com/xYvv6GI.jpg)
To expand on the graph, it is showing the "critical" resonant cycle length which is the highest cycle a corridor can run that will still achieve perfect 2-way signal progression. So if the critical resonant cycle is 90 seconds but the corridor needs to run 120 seconds to fit pedestrians/left turn phases, perfect dual progression is impossible. The generic formula used to plot this graph is the following...
Cycle Length (sec) = 2 X Travel Time
Where Travel Time = Distance / Speed. Assuming distance in feet and speed in mph, the following equation is used....
Cycle Length (sec) = 2 X Distance between signals (feet) / (Speed (mph) X 5280 ft/mile / 3600 sec/hr
Rearranging the equation....
Cycle Length (sec) = (2 X 3600 sec/hr / 5280 ft/mile) X Distance between signals (feet) / Speed (mph)
Simplifying it further, you get the same equation mrsman posted above...
Cycle Length (sec) = (15/11) X Distance between signals (feet) / Speed (mph)
^Now find a random suburban corridor in the country with a 45 mph speed limit. A standard peak hour cycle length (especially if signals along the corridor have left-turn phases) is 120 seconds. At 45 mph hour and a cycle length of 120 seconds, the signals would need to be spaced 3960 feet apart to achieve dual progression. The corridor i choose was Colonial Drive in Orlando. This roughly 2.5 mile section has several irregularly spaced traffic signals spaced much closer then 3960 feet apart. You are just not going to get good signal progression down this road.
(https://i.imgur.com/0kIlTL7.jpg)
Quote from: Brandon on October 31, 2017, 10:10:30 AM
Extinct in most of Illinois (downtown Ottawa has it), it is fairly common in most of Michigan.
Examples:
The only traffic light the driver gets stopped at in the first 17 mile stretch (from Eureka to 18 Mile) is the SPUI at I-94. Good signal progression may be a foreign concept for most cities, but when you drive down a corridor like Telegraph, progression destroying interchanges - like SPUI's - become painfully obvious. Maybe it's not such a big deal to kill signal progression along some corridors, but Telegraph has traffic volumes comparable to many freeways... it's a major corridor in Detroit. There are locations where SPUI's make sense, but I-94 / Telegraph isn't one of them (especially considering MDOT had so much ROW to work with when they were designing this interchange... the free-flowing interchange this SPUI replaced had a massive footprint).
Here's another long drive down Telegraph where the driver doesn't get stopped at very many red lights (just one soft-stop). This video extends to Dixie Highway which is also timed pretty well, but unlike Telegraph you don't get dual progression down Dixie.
https://www.youtube.com/watch?v=Wkf7iLSblZ0
Quote from: tradephoric on November 07, 2017, 12:13:08 PM
The only traffic light the driver gets stopped at in the first 17 mile stretch (from Eureka to 18 Mile) is the SPUI at I-94. Good signal progression may be a foreign concept for most cities, but when you drive down a corridor like Telegraph, progression destroying interchanges - like SPUI's - become painfully obvious. Maybe it's not such a big deal to kill signal progression along some corridors, but Telegraph has traffic volumes comparable to many freeways... it's a major corridor in Detroit. There are locations where SPUI's make sense, but I-94 / Telegraph isn't one of them (especially considering MDOT had so much ROW to work with when they were designing this interchange... the free-flowing interchange this SPUI replaced had a massive footprint).
Personally, I think the SPUI at I-94 and Telegraph would be a good candidate to replace with a DDI. Instead of three cycles, you'd have two. That would be more in place with the typical signal progression along Telegraph.
Sometimes other traffic concerns are more important than signal progression.
Quote from: 1 on October 31, 2017, 05:38:45 AM
Michigan does it pretty well, as do the one-way avenues in New York City. It doesn't exist where I live.
And yes, the first light should be missed; it's green for people going straight, not people coming from a turn.
I don't see how Michigan does it that well it's about the same as anywhere else. You can get on roads here that'll make you stop at every light you encounter. Last night I was driving EB on M-46 coming into Saginaw and had to stop for the light at the entrance to Meijer at 11:30pm while the light at Miller Road was flashing, the light at River Road was flashing and the light at Midland Road (M-47) another state highway was flashing. While I was waiting for that light I thought to myself why in the hell is this light operating like this while all the other one's are flashing?
Quote from: Flint1979 on November 08, 2017, 06:08:34 AM
I don't see how Michigan does it that well it's about the same as anywhere else. You can get on roads here that'll make you stop at every light you encounter. Last night I was driving EB on M-46 coming into Saginaw and had to stop for the light at the entrance to Meijer at 11:30pm while the light at Miller Road was flashing, the light at River Road was flashing and the light at Midland Road (M-47) another state highway was flashing. While I was waiting for that light I thought to myself why in the hell is this light operating like this while all the other one's are flashing?
Meijer likely has a cost participation agreement with MDOT for the traffic light at their entrance and they have a say to how the light operates. Since most Meijer's are open 24 hours a day, it's not surprising that the signal was operating at 11:30 PM. But if all the other MDOT lights on M-46 were in flash, then there really isn't much signal progression to speak of (there needs to be more than one traffic signal to coordinate). As you have alluded to, MDOT flashes many signals in the middle of the night. Heck, they flash signals at freeway interchanges and major 4-phase intersections with left turn phases in the middle of the night. But to me that's not a bad thing. Personally, I don't understand your complaint. Go to other states. Many states cycle every signal 24/7... and you'll be getting stopped at more than just that Meijer light I promise you.
EDIT: By the way, i presume all the traffic lights were flashing yellow for you on M-46, so you didn't have to stop?
Quote from: tradephoric on November 05, 2017, 12:36:39 PM
^Now find a random suburban corridor in the country with a 45 mph speed limit. A standard peak hour cycle length (especially if signals along the corridor have left-turn phases) is 120 seconds. At 45 mph hour and a cycle length of 120 seconds, the signals would need to be spaced 3960 feet apart to achieve dual progression. The corridor i choose was Colonial Drive in Orlando. This roughly 2.5 mile section has several irregularly spaced traffic signals spaced much closer then 3960 feet apart. You are just not going to get good signal progression down this road.
(https://i.imgur.com/0kIlTL7.jpg)
With spacing such as this, I wonder if it's better just to try to have them all be green at one time, then red at one time.
The trouble will be that if the side roads all have varying traffic demands, and left turn channels have varying traffic demands, they all won't be able to turn green at the same time. But, they should all be able to turn red at the same time, and then they cycle to the side street for whatever traffic they have.
You won't fly thru every intersection. But if you stop at about 25% of them, that's better than needing to stop at half of them or greater!
Quote from: Scott5114 on November 08, 2017, 06:00:37 AM
Sometimes other traffic concerns are more important than signal progression.
+1
Why do we think a signal is failing at its job just because it's hard to catch a green?
Quote from: jeffandnicole on November 08, 2017, 01:30:51 PM
Quote from: tradephoric on November 05, 2017, 12:36:39 PM
^Now find a random suburban corridor in the country with a 45 mph speed limit. A standard peak hour cycle length (especially if signals along the corridor have left-turn phases) is 120 seconds. At 45 mph hour and a cycle length of 120 seconds, the signals would need to be spaced 3960 feet apart to achieve dual progression. The corridor i choose was Colonial Drive in Orlando. This roughly 2.5 mile section has several irregularly spaced traffic signals spaced much closer then 3960 feet apart. You are just not going to get good signal progression down this road.
(https://i.imgur.com/0kIlTL7.jpg)
With spacing such as this, I wonder if it's better just to try to have them all be green at one time, then red at one time.
The trouble will be that if the side roads all have varying traffic demands, and left turn channels have varying traffic demands, they all won't be able to turn green at the same time. But, they should all be able to turn red at the same time, and then they cycle to the side street for whatever traffic they have.
You won't fly thru every intersection. But if you stop at about 25% of them, that's better than needing to stop at half of them or greater!
This is a video that compares 3nd Avenue (a one-way street) and Park Avenue (a two-way street) in Manhattan. The main point of the video is to show that the driver on the one-way street is limited to driving whatever speed the traffic lights are timed for. Once they are near the start of the "˜green wave', the approaching red lights throttle back their speed even if they wish to drive faster. OTOH, the simultaneous greens of Park Avenue incentivizes drivers to drive as fast as they can, since the faster they drive the more green lights they will make it through before the string of green lights turn back to red.
https://www.youtube.com/watch?v=6l7XbNK9M2s
Cities keep going back and forth on which is better... one-way or two-way streets. There are some legit reasons why you may want to convert a one-way street back to a two-way street, but there is also a lot of disinformation out there. For instance, proponents of two-way streets will often argue that since the average speed of traffic on a two-way street is lower than a one-way street, that two-way streets are safer for pedestrians. But the average speed is based on travel time runs which account for both the time a vehicle is moving and the time they are stuck at a red light. It's hard to kill a pedestrian when a vehicle is traveling 0 mph at a red light.
Quote from: tradephoric on November 08, 2017, 02:38:42 PM
It's hard to kill a pedestrian when a vehicle is traveling 0 mph at a red light.
Unless the car runs the red for any number of factors, to name a few: distrated driving, sudden medical affliction(s), intoxication, evading police, etc.
Quote from: TheArkansasRoadgeek on November 08, 2017, 03:08:34 PM
Quote from: tradephoric on November 08, 2017, 02:38:42 PM
It's hard to kill a pedestrian when a vehicle is traveling 0 mph at a red light.
Unless the car runs the red for any number of factors, to name a few: distrated driving, sudden medical affliction(s), intoxication, evading police, etc.
It's hard to run a red light when a vehicle is travelling 0 mph. :biggrin:
Quote from: tradephoric on November 08, 2017, 10:33:18 AM
Quote from: Flint1979 on November 08, 2017, 06:08:34 AM
I don't see how Michigan does it that well it's about the same as anywhere else. You can get on roads here that'll make you stop at every light you encounter. Last night I was driving EB on M-46 coming into Saginaw and had to stop for the light at the entrance to Meijer at 11:30pm while the light at Miller Road was flashing, the light at River Road was flashing and the light at Midland Road (M-47) another state highway was flashing. While I was waiting for that light I thought to myself why in the hell is this light operating like this while all the other one's are flashing?
Meijer likely has a cost participation agreement with MDOT for the traffic light at their entrance and they have a say to how the light operates. Since most Meijer's are open 24 hours a day, it's not surprising that the signal was operating at 11:30 PM. But if all the other MDOT lights on M-46 were in flash, then there really isn't much signal progression to speak of (there needs to be more than one traffic signal to coordinate). As you have alluded to, MDOT flashes many signals in the middle of the night. Heck, they flash signals at freeway interchanges and major 4-phase intersections with left turn phases in the middle of the night. But to me that's not a bad thing. Personally, I don't understand your complaint. Go to other states. Many states cycle every signal 24/7... and you'll be getting stopped at more than just that Meijer light I promise you.
EDIT: By the way, i presume all the traffic lights were flashing yellow for you on M-46, so you didn't have to stop?
I regularly report gas prices along Gratiot (M-46) on Gasbuddy so I'm out that way quite a bit. I never really noticed if it flashes later into the night. The entrance is kind of strange because it's really a side street that goes on the side of Meijer next to the gas station. I thought that this light flashed at some point of the night, possibly it starts flashing at midnight.
Yes the rest of them were flashing yellow, I forget if the one at Graham Road (M-52) was flashing but it seems like it was, I was on M-46 until Center which was also flashing, Miller, River, Midland, Frost and Center all were.
Quote from: kphoger on November 08, 2017, 03:18:31 PM
Quote from: TheArkansasRoadgeek on November 08, 2017, 03:08:34 PM
Quote from: tradephoric on November 08, 2017, 02:38:42 PM
It's hard to kill a pedestrian when a vehicle is traveling 0 mph at a red light.
Unless the car runs the red for any number of factors, to name a few: distrated driving, sudden medical affliction(s), intoxication, evading police, etc.
It's hard to run a red light when a vehicle is travelling 0 mph. :biggrin:
Exactly! But to ArkansasRoadGeek's point there will always be isolated incidents where distracted drivers completely blow through a red light. But what distracted driver is more likely to blow through a red light in that video? The one-way driver who gets an endless string of green lights as long as they keep up with the flow of traffic, or the two-way driver who is guaranteed to encounter a red light every minute or so (since Park Avenue is timed for simultaneous greens and a red light is inevitably coming). The one-way driver can be playing Candy Crush on their phone, glancing up every 10 seconds to the road, and they still may have trouble blowing through a red light. It's just hard to "catch" a red light on a properly timed one-way street. OTOH, it's really easy to "catch" a red light on a two way road where traffic signals are spaced closely together.
Quote from: tradephoric on November 08, 2017, 03:45:46 PM
there will always be isolated incidents where distracted drivers completely blow through a red light roundabout.
You did know that was coming, right? :D
Quote from: kphoger on November 08, 2017, 03:47:48 PM
Quote from: tradephoric on November 08, 2017, 03:45:46 PM
there will always be isolated incidents where distracted drivers completely blow through a red light roundabout.
You did know that was coming, right? :D
LOL I was expecting that! To improve intersection safety, retractable bollards should extend up from the roadway when a signal turns red. That way if anyone blows through a red light, they will crash into the sturdy posts before they have a chance of t-boning anybody in the intersection. No more need for roundabouts! Here is a crash test to simulate how safe an intersection would become when someone tries to blow through a red light!
https://www.youtube.com/watch?v=9FfUlojxiqE
Quote from: tradephoric on November 08, 2017, 04:09:53 PM
Quote from: kphoger on November 08, 2017, 03:47:48 PM
Quote from: tradephoric on November 08, 2017, 03:45:46 PM
there will always be isolated incidents where distracted drivers completely blow through a red light roundabout.
You did know that was coming, right? :D
LOL I was expecting that! To improve intersection safety, retractable bollards should extend up from the roadway when a signal turns red. That way if anyone blows through a red light, they will crash into the sturdy posts before they have a chance of t-boning anybody in the intersection. No more need for roundabouts! Here is a crash test to simulate how safe an intersection would become when someone tries to blow through a red light!
https://www.youtube.com/watch?v=9FfUlojxiqE
What about emergency response needing to drive through red lights?
Quote from: tradephoric on November 08, 2017, 04:09:53 PM
LOL I was expecting that! To improve intersection safety, retractable bollards should extend up from the roadway when a signal turns red. That way if anyone blows through a red light, they will crash into the sturdy posts before they have a chance of t-boning anybody in the intersection. No more need for roundabouts! Here is a crash test to simulate how safe an intersection would become when someone tries to blow through a red light!
I'm hoping this wasn't a serious recommendation...
Quote from: roadfro on November 09, 2017, 10:29:31 AM
Quote from: tradephoric on November 08, 2017, 04:09:53 PM
LOL I was expecting that! To improve intersection safety, retractable bollards should extend up from the roadway when a signal turns red. That way if anyone blows through a red light, they will crash into the sturdy posts before they have a chance of t-boning anybody in the intersection. No more need for roundabouts! Here is a crash test to simulate how safe an intersection would become when someone tries to blow through a red light!
I'm hoping this wasn't a serious recommendation...
If it were, I can just imagine the carnage cause by the bollards in Chicago where red light running is a popular sport.
Quote from: roadfro on November 09, 2017, 10:29:31 AM
Quote from: tradephoric on November 08, 2017, 04:09:53 PM
LOL I was expecting that! To improve intersection safety, retractable bollards should extend up from the roadway when a signal turns red. That way if anyone blows through a red light, they will crash into the sturdy posts before they have a chance of t-boning anybody in the intersection. No more need for roundabouts! Here is a crash test to simulate how safe an intersection would become when someone tries to blow through a red light!
I'm hoping this wasn't a serious recommendation...
I do think retractable bollards to stop red light runners would be a terrible idea. But I also think it's a terrible idea to have immovable fixed objects in the central islands of roundabouts (especially at suburban roundabouts where approaching speeds are high). In the roundabout thread I pointed out that there have been 3 fatalities at the 96th and Westfield roundabout in Carmel. In each instance the driver struck a concrete wall in the middle of the central island. Just like the crash video of the truck striking those bollards, it can be a vicious crash when a driver blows through the middle of a roundabout and strikes a concrete wall. Many people defended the fixed objects in the middle of roundabouts, arguing that it prevented drivers from blowing through the roundabout completely and potentially hitting a vehicle on the other side.
Quote from: cpzilliacus on May 20, 2015, 03:34:14 PMThis roundabout (https://www.google.com/maps/place/Mt+Rainier,+MD/@38.936294,-76.960984,3a,26.4y,47.29h,81.51t/data=!3m4!1e1!3m2!1s469xw_VJTQOCuZtYSmrG7A!2e0!4m2!3m1!1s0x89b7c7a0d961e31f:0x38df1d15661676d1!6m1!1e1) features a rather massive concrete "planter" inside, which gets crashed into somewhat often by drunk/impaired drivers headed out of D.C.
I don't think it is poorly designed, and it improves Maryland traffic safety by "intercepting" some of those impaired motorists before they crash into something else, or a pedestrian or bicyclist.
Quote from: cjw2001 on August 23, 2016, 02:02:23 PMIf you drive like an idiot you live (or die) with the consequences. These are the same people that would have blown the stop sign and taken out another car when it was a stop controlled intersection -- I'm much happier with them being stopped by an inanimate object rather than another vehicle.
Quote from: jeffandnicole on August 24, 2016, 12:25:46 PMYou never know...there could've been someone traveling on the other side of the roundabout, and the boulder saved the idiot driver from plowing thru the median into their car, killing them instead.
If you think about it, fixed objects in the central islands of roundabouts only protects the circulating vehicles on the far side of the roundabout. What about the circulating vehicles on the near side of the roundabout who are in between the concrete wall and the vehicle blowing through the roundabout? They are still in danger of being t-boned. With the retractable bollards, all vehicles in the intersection would be protected as the bollards would prevent the red light runner from ever entering the intersection. Retractable bollards at signalized intersections would protect 100% of drivers already in the intersection, while fixed objects in the central islands of roundabouts only protects 50% of the drivers (the drivers circulating on the far side of the roundabout when somebody blows through it). So signalized intersections with retractable bollards would be twice as safe as roundabouts with fixed objects in the central islands :D
After driving down the "free" frontage roads which parallel the Toll Roads in Dallas this past week (S. Rayburn, G. Bush,...), it seemed to me they were perfectly timed to make you stop at every light, in order to make you "consider" how much faster you could get to your destination had you paid $$$ to use the Tollway instead.
Here's another question for those who are familiar with Detroit-area corridors like Woodward and Telegraph that feature great two-way progression:
If Woodward intersects a relatively minor street at a traffic signal, are the traffic signals tied in to a pre-arranged timing sequence in order to maintain progression (i.e. traffic on Woodward would always get a red at the pre-ordained time in the cycle, even if there is no traffic on the side street) or are the signals demand sensitive (resting on green favoring Woodward, only turning red if both at the preordained time in the cycle and if there is demand from the side street.)
I've wondered if demand-based triggering, which is generally a good thing, would have adverse effects on a carefully engineered traffic progression plan.
In NYC, the vast majority of signals are set by timer. The one-way progression on the avenues is set into the timing, but they will face red lights even if there is no cross traffic at the wrong side of the cycle.
As far as the true N/S or E/W main roads in Metro Detroit (Telegraph, n-Mile Road,...) All the lights are on a timed cycle, so the side streets -- and in the case of Telegraph Road with the lights at a U-Turn/Michigan Left intersection -- the lights will change whether or not someone is waiting for a green light off of Telegraph.
With the "spoke" roads in the Detroit area that are moreso angled (Grand River, Dix, Woodward, Gratiot,...) than true N/S or E/W "grid" roads, I'm sure they are timed for the main artery as best as possible. It's when those streets intersect the main grid roads as to how the timings are set.
Most of my Detroit travels were usually south of 8-Mile and west of the Southfield Freeway, so it was pretty much all grid-based roads. If you averaged 45 MPH on any grid road, you were pretty much good to go in any direction, as far as hitting green lights goes.
Quote from: mrsman on November 13, 2017, 07:13:45 PM
Here's another question for those who are familiar with Detroit-area corridors like Woodward and Telegraph that feature great two-way progression:
If Woodward intersects a relatively minor street at a traffic signal, are the traffic signals tied in to a pre-arranged timing sequence in order to maintain progression (i.e. traffic on Woodward would always get a red at the pre-ordained time in the cycle, even if there is no traffic on the side street) or are the signals demand sensitive (resting on green favoring Woodward, only turning red if both at the preordained time in the cycle and if there is demand from the side street.)
They typically are timed for signal progression in order to maximize throughput on the main road (i.e. Woodward, Telegraph, etc). After a certain hour, many of them may flash yellow for the main street and flash red for the side street (like between 10 pm and 5 am).
Quote from: mrsman on November 13, 2017, 07:13:45 PM
I've wondered if demand-based triggering, which is generally a good thing, would have adverse effects on a carefully engineered traffic progression plan.
If you ever want to see demand-based triggering all the time, 24/7, go to Chicago's suburbs. Every signal there is triggered, and it makes it a right royal pain in the ass to keep going at the speed limit on a major thoroughfare like North Avenue or IL-59.
Quote from: Brandon on November 14, 2017, 09:45:56 AM
If you ever want to see demand-based triggering all the time, 24/7, go to Chicago's suburbs. Every signal there is triggered, and it makes it a right royal pain in the ass to keep going at the speed limit on a major thoroughfare like North Avenue or IL-59.
I drove north on Naper Blvd/Naperville Rd for five miles or more late at night one time, along with basically one other driver. I eased away from the lights when they changed green, kept it under the speed limit. He gunned it off the line and drove about 5 to 10 mph over the limit. Our progress was exactly the same, because he kept getting stuck at red lights triggered by cross traffic, and I kept rolling up right around the time they were changing to green again.
I get frustrated sitting at red lights that I feel are unnecessary, so I learned not to try and rush in the Chicago suburbs late at night. There's no point. But I'd still rather sit at a red light triggered by a single car that ended up turning right anyway, than sit at a red light with no cross traffic at all. I hate timed lights in general, even if I understand they might actually benefit my travel overall.
Quote from: mrsman on November 13, 2017, 07:13:45 PM
Here's another question for those who are familiar with Detroit-area corridors like Woodward and Telegraph that feature great two-way progression:
If Woodward intersects a relatively minor street at a traffic signal, are the traffic signals tied in to a pre-arranged timing sequence in order to maintain progression (i.e. traffic on Woodward would always get a red at the pre-ordained time in the cycle, even if there is no traffic on the side street) or are the signals demand sensitive (resting on green favoring Woodward, only turning red if both at the preordained time in the cycle and if there is demand from the side street.)
I've wondered if demand-based triggering, which is generally a good thing, would have adverse effects on a carefully engineered traffic progression plan.
In NYC, the vast majority of signals are set by timer. The one-way progression on the avenues is set into the timing, but they will face red lights even if there is no cross traffic at the wrong side of the cycle.
what does cop / fire traffic light preemption due to that?
train traffic light preemption?
Take a look down Big Beaver in Troy, Michigan. The only traffic signals that stop both directions of travel along this stretch are at major mile roads. The turnarounds along the wide-medians help eliminate the need for half-mile signals that ruin progression.
(https://i.imgur.com/US9wyhE.jpg)
Compare that to a standard undivided roadway. Now seemingly every church, school, and strip mall along the stretch of road warrants its own traffic signal. You end up with a string of traffic signals between major mile roads that stop both directions of travel and kills signal progression. Instead of coordinating 2 lights along a 2 mile stretch, you have to coordinate 10 lights. When there are so many traffic signals spaced closely together, they will often be timed to turn green and switch back to red simultaneously. That's a tell-tale sign the road isn't going to have good 2-way progression.
(https://i.imgur.com/SZWudj3.png)
In the first picture, I see traffic bunched up and tailgating. In the 2nd picture, traffic appears to be progressing nicely.
Then again, in the 2nd shot, that's in a downtown area where you want to keep speeds slow anyway. https://goo.gl/maps/huWty3jtSVE2 That said, I don't see any issues with that 2nd picture. The first picture appears to have some congestion issues.
/me cringes.
Quote from: jeffandnicole on November 14, 2017, 02:03:51 PM
In the first picture, I see traffic bunched up and tailgating. In the 2nd picture, traffic appears to be progressing nicely.
Then again, in the 2nd shot, that's in a downtown area where you want to keep speeds slow anyway. https://goo.gl/maps/huWty3jtSVE2 That said, I don't see any issues with that 2nd picture. The first picture appears to have some congestion issues.
The 2nd picture probably isn't a great comparison (since it isn't a typical suburban corridor) but the theory still applies. There was a video already posted driving a 5-mile section of Big Beaver in both directions without getting stuck at a red light (apart from when the driver turns around to demonstrate the dual progression). I'll point out that at 3:55 the driver just makes it through a yellow light which is annoying because there is no legitimate reason for that crossover signal to be out of step with the surrounding signals. Unfortunately that signal was malfunctioning (it had been out of step like that for days), which goes to show that even a corridor that is capable of great signal progression doesn't always achieve it.
Traveling 40 miles down Woodward Avenue without hitting a red light. During the nearly hour long drive, the driver makes it through 124 consecutive green lights.
https://www.youtube.com/watch?v=mb2R2fPB1nE&feature=youtu.be
https://jalopnik.com/oregon-admits-violating-the-constitutional-rights-of-re-1821086560#js_discussion-region
Thought this might be useful to some showing how old our signal timing formula is.
If you want to rant about him getting fined unconstitutionally, I've started a thread over in Northwest about that with Oregon specific red light (speeding) camera usage.
See Boulton Street between Route 24 and Tollgate Road in Bel Air, Maryland. When a light went up at Boulton and Gateway in 2012 very close to the one at the northern entrance of the Harford Mall/main entrance of the Harford Mall Annex (there's a side entrance on Gateway), the Town of Bel Air did a great job reconfiguring the lights at Route 24, the Mall/Annex and Tollgate to accomodate the light at Gateway and preserve the overall flow of traffic on that segment of Boulton, paying special attention to the Mall/Annex light.
Also relatively close by to me is Route 146 in the north Towson area between Pot Spring Road and the Interstate 695 Beltway interchange. That one varies between good and not so good. One of the determining factors is rush hour. It is not uncommon in the evening for traffic southbound on 146 to have a green light at Pot Spring only to have to stop within or prior to the Pot Spring intersection because they have a red light at the next intersection, Seminary Avenue, which is very close by. The following pair of lights, Charmuth Lane and Hampton Lane/ramp to the I-695 outer loop, has the same situation.
So on minor sidestreets intersecting with a major throughway, what is preferred as the "perfect" signal timing? I've noticed some areas have the side streets stay green longer then necessary, while others all try to "perfect" the timing of the red lights, while the green lights are just ASAP based on the sensors on the side streets, I assume figuring that some intersections are going to be dumping different amount of cars on the road and to get through the queue takes different amounts of time anyways...