Trafic Light Cameras

[agentsteel53]

I'd like to have yellow lights come with a countdown timer so I can make decisions more intelligently.

green and red ones, too.

[Scott5114]

Sometimes you need to be able to go through yellow or red lights–for safety reasons (to avoid a rear-ending), in the event of a signal malfunction (should you really have to sit at a red light at 2 AM for 20 minutes because the detector loop didn't register your car), emergency (driving someone to the hospital), other exceptional circumstances (it's an inner city area and there appears to be a menacing looking gang walking towards your car with the intent to rob you). It would be nice if we didn't have to suffer a damned-if-you-do-damned-if-you-don't dilemma because some politician wanted to make the city a few extra bucks–which is what most of these red light cameras seem to be, not a real attempt to deter blatant red light running.

[SidS1045]

I'd like to invite anyone in the anti-red light camera camp to have their car totaled by a red light runner, as mine was a few months ago in an incident where I was fortunate to avoid serious injury.  Would such an installation prevented the accident?  Maybe, maybe not, but I'd feel better that some entity was trying something to use as a deterrent.

A nice appeal to emotion, but it's not supported by facts.  Red-light running is not nearly the monstrous problem the so-called safety lobby makes it out to be.  The costs of installation and enforcement keep a lot of people employed and statistically do absolutely nothing for the safety of intersections with traffic signals...except, in some cases, to increase the incidence of rear-end collisions as drivers no longer recognize the timing of yellow lights and slam on their brakes when they don't have to, to avoid being ticketed.

As I stated above, follow the money.  Cash-strapped municipalities see a source for ready cash and fall for it, hook, line and sinker.  Never mind that they are farming out traffic safety to private companies with vested interests, not the least of which is collecting a fee per ticket issued.  (No conflict of interest there, huh?)  Never mind that in too many cases, where there aren't enough tickets being issued to make the cameras pay, the yellow-light interval is shortened, contrary to the principles of traffic engineering, which inevitably increases rear-end collisions and makes violators out of otherwise law-abiding citizens.

If there are drivers running red lights, maybe the cause ought to be found through a traffic engineering study, rather than just ticketing everyone (which is no deterrent anyhow, since camera tickets arrive in the mail long after the alleged violation has occurred).

[agentsteel53]

A nice appeal to emotion, but it's not supported by facts.  Red-light running is not nearly the monstrous problem the so-called safety lobby makes it out to be.  

indeed.  I've had two cars totaled by red-light runners and I still don't cameras are the solution.

again, the solution is twofold: 1) more information during all phases, like a countdown timer for yellows - especially short yellows like 4 seconds on the 70mph section of TX-71 - and 2) execute anyone who runs the red light because they are too fucking stupid to pay attention.

[Brandon]

I'd like to invite anyone in the anti-red light camera camp to have their car totaled by a red light runner, as mine was a few months ago in an incident where I was fortunate to avoid serious injury.  Would such an installation prevented the accident?  Maybe, maybe not, but I'd feel better that some entity was trying something to use as a deterrent.

A nice appeal to emotion, but it's not supported by facts.  Red-light running is not nearly the monstrous problem the so-called safety lobby makes it out to be. 

Exactly.  The estimates from Schaumburg, IL, are that approximately 90+% of the violations were for rolling past the stop line for a right on red.  When the village decided to bow to public outcry and stop ticketing ROR, revenues plummeted to a point at which the cameras could not be sustained.  The village got rid of them a couple of months later.

Even Naperville has ended their contract for much the same reason.  They had to remove the two they had on IL-59 (road construction starts this spring), and in doing so, they admitted that the revenues from the other one at Ogden and Aurora Avenues were not enough to keep the system.

[SidS1045]

The estimates from Schaumburg, IL, are that approximately 90+% of the violations were for rolling past the stop line for a right on red.  When the village decided to bow to public outcry and stop ticketing ROR, revenues plummeted to a point at which the cameras could not be sustained.  The village got rid of them a couple of months later.

Even Naperville has ended their contract for much the same reason.  They had to remove the two they had on IL-59 (road construction starts this spring), and in doing so, they admitted that the revenues from the other one at Ogden and Aurora Avenues were not enough to keep the system.

Moral of the story:  Properly engineered roads and intersections don't invite red-light running.  The National Motorists Association did a study of red-light cameras (which they vehemently oppose on several grounds) and found that in every case they studied (IIRC, about 60 or so), there were one or more engineering errors at each intersection which, if corrected, would drastically reduce the instances of red-light running.

[SidS1045]

more information during all phases, like a countdown timer for yellows - especially short yellows like 4 seconds on the 70mph section of TX-71

A four-second yellow in a 70mph zone is a disaster waiting to happen, and will essentially invite red-light running and/or rear-end collisions by the dozen.  The usual rule of engineering traffic signals at an intersection is one second of yellow light per 10mph of legal speed.  Those signals on TX-71 should be yellow for seven seconds, not four.

I'll bet there are a lot of skid marks at that TX-71 intersection.

[stormwatch7721]

Daytona Beach has the red light cameras.

[NE2]

Hey guys! Let's list every place that has them!

(Let's not.)

[agentsteel53]

A four-second yellow in a 70mph zone is a disaster waiting to happen, and will essentially invite red-light running and/or rear-end collisions by the dozen.  The usual rule of engineering traffic signals at an intersection is one second of yellow light per 10mph of legal speed.  Those signals on TX-71 should be yellow for seven seconds, not four.

in general, I don't think traffic lights should be used when the speed of traffic is greater than about 60.  not only are people less likely to know their car's own stopping distance (how often do you have to come from 75mph to a dead stop?  much, much less frequently than from even 65), but with the variability in yellow-light durations, it's a disaster waiting to happen. 

again, I would really like lights to come with countdown timers.  at some intersections, I know I can use the pedestrian timer to give me a couple more hints of information, as even when it is inaccurate, it is inaccurate in my favor: namely, the light turns yellow either at "0", or several seconds after... it would never go from green to yellow while pedestrians are still crossing - a full red, pedestrians-only phase is orchestrated completely differently.

[NE2]

It would be useful to have a marking on the road, basically "if you're going the speed limit and the light turns yellow before you reach this, you can easily stop in time". The yellow should then be calibrated to give someone who just passed it more than enough time to get through.

[agentsteel53]

It would be useful to have a marking on the road, basically "if you're going the speed limit and the light turns yellow before you reach this, you can easily stop in time". The yellow should then be calibrated to give someone who just passed it more than enough time to get through.

I have always thought that the boundary where dashed lane-separator lines turn into solid ones is the start of that point.  

I do not consider this gospel of course, but it seems to be intuitively correct to a small margin of error... except in cases where the speed of traffic is over 60; in which situations the solid lines seem far too short.

maybe that's why I am so against high-speed signal-controlled intersections???

[Alps]

again, I would really like lights to come with countdown timers.  at some intersections, I know I can use the pedestrian timer to give me a couple more hints of information, as even when it is inaccurate, it is inaccurate in my favor: namely, the light turns yellow either at "0", or several seconds after... it would never go from green to yellow while pedestrians are still crossing - a full red, pedestrians-only phase is orchestrated completely differently.

Not at all true, nationally. I've seen pedestrian timers extend through the yellow phase.

It would be useful to have a marking on the road, basically "if you're going the speed limit and the light turns yellow before you reach this, you can easily stop in time". The yellow should then be calibrated to give someone who just passed it more than enough time to get through.

I have always thought that the boundary where dashed lane-separator lines turn into solid ones is the start of that point.  

I like your idea and think the MUTCD should require it above 35 mph.

[agentsteel53]

Not at all true, nationally. I've seen pedestrian timers extend through the yellow phase.

I cannot recall an example of this occurring.  I have seen the timerless flashing orange pedestrian "finish crossing, but do not start" extend through yellow, but never a white with a timer or an orange with a timer.

[Alps]

Not at all true, nationally. I've seen pedestrian timers extend through the yellow phase.

I cannot recall an example of this occurring.  I have seen the timerless flashing orange pedestrian "finish crossing, but do not start" extend through yellow, but never a white with a timer or an orange with a timer.

Start off with Massachusetts. I may have also seen it in Wisconsin, but I may have also not.

[agentsteel53]

Start off with Massachusetts. I may have also seen it in Wisconsin, but I may have also not.

wait, that sounds vaguely familiar.

do they ever extend the pedestrian time into the red?  I just recall myself thinking "if I make it through the intersection before the timer hits 0, I am good to go" but clearly this isn't something I've consciously analyzed!

[roadfro]

Sorry for multiple messages... In an effort to provide pertinent replies and not mix up information, I'm responding to different concepts in each post.

A four-second yellow in a 70mph zone is a disaster waiting to happen, and will essentially invite red-light running and/or rear-end collisions by the dozen.  The usual rule of engineering traffic signals at an intersection is one second of yellow light per 10mph of legal speed.  Those signals on TX-71 should be yellow for seven seconds, not four.

Actually, the commonly accepted standard for determining the change interval (yellow time) is the formula recommended by the Institute of Transportation Engineers (ITE):

Y = T + [1.47*S / (2D + 64.4*0.01*G)]

Where:
Y is the computed yellow change interval (s),
T is the "perception/reaction" time (s) [i.e. how long at onset of yellow it takes a driver to react to the yellow, often assumed as 1.0s],
S is the 85th percentile speed (mph) [in practice, often assumed to be the posted speed limit; sometimes approach speed is used if known],
D is an assumed deceleration rate (ft/s) [often assumed as 10ft/s], and
G is the uphill or downhill grade of the approach in percent.

Taking the situation described above, using typical values and assuming it is a flat approach (so the grade term drops to 0), the equation gives about 6.1 seconds of yellow time for the 70mph approach.

In any case, it is recommended to have a minimum yellow change interval of 3 seconds and I believe a maximum of 7 seconds.

[roadfro]

It would be useful to have a marking on the road, basically "if you're going the speed limit and the light turns yellow before you reach this, you can easily stop in time". The yellow should then be calibrated to give someone who just passed it more than enough time to get through.

I have always thought that the boundary where dashed lane-separator lines turn into solid ones is the start of that point.  

I do not consider this gospel of course, but it seems to be intuitively correct to a small margin of error... except in cases where the speed of traffic is over 60; in which situations the solid lines seem far too short.

What NE2 describes basically would amount to solving the dilemma zone issue for motorists.  Dilemma zone is a hard concept to explain in words without diagrams and the ability to elaborate. The basic idea is that, given a speed of arriving vehicle, there is an area some distance from the intersection that a vehicle can neither safely stop nor safely pass through the intersection at the onset of yellow. There are formulas for determining the safe passing and safe stopping distances which could eliminate the dilemma zone; these are based on speed and other factors. The problem with providing some kind of marking or sign for motorists and actually eliminating the dilemma zone is that it only works for the exact speed used in the calculation...any other speed above or below will render the warning useless by either being too conservative or too liberal, and drivers would end up disregarding them.

Using the point at which the broken line turns solid, as Jake suggests, can be a decent rule of thumb. However, it is not completely reliable as that distance is often set by DOT or agency standard without regard to signal timing (or, as is typical in Nevada, the solid line is rarely used in this manner for through lanes at signals).

[roadfro]

again, I would really like lights to come with countdown timers.

The problem with providing vehicular countdown timers (other than the fact that the MUTCD forbids them) is that doing so requires a green time to be fixed. This might work well for downtown grids and other areas operating fixed-time signals. However, many signals do not operate in this manner. With actuated signals (i.e. where detection is used), each signal phase has different components called a initial green, vehicle extension (also known as a passage gap) and maximum green. Each time the phase turns green, the signal must run for the initial green time plus extension. The extension is a short internal countdown timer. So if no vehicles are detected upstream during the first extension, the phase goes to red; however, if a vehicle is detected in that short time, that extension countdown resets and begins counting down again. The extension timer can continue resetting every time a new vehicle is detected upstream, up until the phase reaches the maximum green time at which point the phase is forced to turn yellow.

A visible vehicle countdown timer would be pretty useless if it counted down to any point in the cycle other than the beginning of the yellow. With the green time components described above, a phase's green time could be as little as 5 seconds or as long as 40 seconds or more. There is no way for a signal to know exactly when it will turn yellow using these settings. This is the main reason why such countdowns are not in use--there are other factors as well, such as emergency preemption.

[roadfro]

at some intersections, I know I can use the pedestrian timer to give me a couple more hints of information, as even when it is inaccurate, it is inaccurate in my favor: namely, the light turns yellow either at "0", or several seconds after... it would never go from green to yellow while pedestrians are still crossing - a full red, pedestrians-only phase is orchestrated completely differently.

Not at all true, nationally. I've seen pedestrian timers extend through the yellow phase.

The pedestrian countdown timer can be a reasonable substitute for a vehicle countdown, but cannot be relied on 100%. Again, this is something that depends on the controller settings and agency policy. Many agencies use the safe route of having the "0" appear at the onset of yellow (this allows additional time for pedestrians to clear), but it is MUTCD-acceptable to have the countdown last through the end of yellow. It all depends on the agency's policy regarding the relationship between pedestrian clearance time and mandatory buffer time, and whether these overlap. There's also the fact that the signal could count down and end way before yellow...that could result from green extensions (as discussed above) or skipping a side street phase.

You also have to make sure you look at the proper pedestrian signal head. Generally this is the one controlling the crosswalk adjacent to the through lanes you are traveling in. Looking at the opposite side may steer you wrong in lead-lag operations (but can also be a bit of an indication as to when the lagging left turn will start).

do they ever extend the pedestrian time into the red?  I just recall myself thinking "if I make it through the intersection before the timer hits 0, I am good to go" but clearly this isn't something I've consciously analyzed!

No, pedestrian time is not extended into the red. According to the 2009 MUTCD, the end of the countdown must be followed by a 3-second minimum buffer period before conflicting traffic is released. According to Figure 4E-9, the pedestrian countdown must terminate by start of red for adjacent through traffic at the latest.

Yes, you are generally correct in thinking that you will be good to go if you make it through the intersection before the timer hits 0. The only complication is whether you're in a "restrictive yellow" state (i.e. illegal to enter on yellow) *and* the countdown continues past onset of yellow.

[agentsteel53]

The problem with providing vehicular countdown timers (other than the fact that the MUTCD forbids them) is that doing so requires a green time to be fixed. This might work well for downtown grids and other areas operating fixed-time signals. However, many signals do not operate in this manner. With actuated signals (i.e. where detection is used), each signal phase has different components called a initial green, vehicle extension (also known as a passage gap) and maximum green. Each time the phase turns green, the signal must run for the initial green time plus extension. The extension is a short internal countdown timer. So if no vehicles are detected upstream during the first extension, the phase goes to red; however, if a vehicle is detected in that short time, that extension countdown resets and begins counting down again.

here I had thought it worked in the opposite manner: the light stays default on green until traffic is detected that is due to come in conflict with the main through traffic: side street traffic, someone wishing to make a protected left turn off the mainline, or a pedestrian pushing the "let me cross" button.

A visible vehicle countdown timer would be pretty useless if it counted down to any point in the cycle other than the beginning of the yellow. With the green time components described above, a phase's green time could be as little as 5 seconds or as long as 40 seconds or more. There is no way for a signal to know exactly when it will turn yellow using these settings. This is the main reason why such countdowns are not in use--there are other factors as well, such as emergency preemption.

my idea for a solution hinges on my previous assumption about what triggers the change (see paragraph above) and would involve the green timer being off (displaying no number) - except when the trigger from the conflicting has been established. 

from my observation, the mainline light changes to yellow within about 5 seconds of the side street traffic appearing, so once this 5 second time has been established, then display a green count.  until then, display no count to indicate that there is no plan for the light to change color.

similarly, the side-street (or turning traffic) red should display no countdown until the conflicting vehicle has successfully been detected - at which point, the red light displays 11 seconds (or whatever the combined total is of the mainline's remaining green, yellow, and then the all-red safety margin)

again, that assumption hinges on the conflicting traffic triggering the light change, as opposed to the absence of mainline traffic... but that assumption seems to jive well with my observations.  so maybe I'm misreading your first paragraph?  can you shed some light on why I'm possibly interpreting this incorrectly?

[agentsteel53]

The only complication is whether you're in a "restrictive yellow" state (i.e. illegal to enter on yellow) *and* the countdown continues past onset of yellow.

honestly, I cannot for the life of me remember which states those are.  that sounds like a fairly brainless rule in general - what if I were traveling 45mph, and I found myself two feet outside of the intersection when the light turned yellow?  Am I expected to come to a dead stop from 45mph in two feet?

I thought not.

I've never, ever, not once, been pulled over for entering an intersection on yellow.  I would assume that would be the "dickness of last resort" when a jurisdiction gets really, really broke but everyone is suddenly coming to a complete stop at four-way stop signs and obeying every speed limit to the letter.

[NE2]

The only complication is whether you're in a "restrictive yellow" state (i.e. illegal to enter on yellow) *and* the countdown continues past onset of yellow.

honestly, I cannot for the life of me remember which states those are.  that sounds like a fairly brainless rule in general - what if I were traveling 45mph, and I found myself two feet outside of the intersection when the light turned yellow?  Am I expected to come to a dead stop from 45mph in two feet?

I thought not.

I've never, ever, not once, been pulled over for entering an intersection on yellow.  I would assume that would be the "dickness of last resort" when a jurisdiction gets really, really broke but everyone is suddenly coming to a complete stop at four-way stop signs and obeying every speed limit to the letter.

The law is that it's illegal to enter on yellow if you can safely stop. In other states, you can enter on yellow no matter what.

[kphoger]

The only time my wife has been pulled over since we've been married has been for entering an intersection on a yellow light.  Princeton, Minnesota.  We were so ticked.

[agentsteel53]

The law is that it's illegal to enter on yellow if you can safely stop. In other states, you can enter on yellow no matter what.

seems like a hell of a judgment call on the part of the witnessing officer.  I'd imagine most of them would enforce it as "no drastic and sudden acceleration to make the yellow".