The Worst of Changeable Message Signs

[Kacie Jane]

The signs use the actual speed of traffic, not the speed limit. Having a travel time sign that shows you the time at the speed limit would be pointless, since it doesn't matter what the speed limit is if the road is congested.

In/around Seattle, if the road is congested, then yes, they use the actual speed of traffic, but they always "max out" at the speed limit. The sign in South Everett 26 miles north of Seattle frequently shows travel times of more than 26 minutes, but never less than 26 minutes.

[deathtopumpkins]

The signs use the actual speed of traffic, not the speed limit. Having a travel time sign that shows you the time at the speed limit would be pointless, since it doesn't matter what the speed limit is if the road is congested.

In/around Seattle, if the road is congested, then yes, they use the actual speed of traffic, but they always "max out" at the speed limit. The sign in South Everett 26 miles north of Seattle frequently shows travel times of more than 26 minutes, but never less than 26 minutes.

The examples in the part of my post you cut out clearly show that Massachusetts does not max them out at the speed limit. Seems much more useful than the WSDOT ones.

Also, wouldn't having the times max out at the speed limit require more work on the part of whoever is programming the back end of the system?

[Central Avenue]

Also, wouldn't having the times max out at the speed limit require more work on the part of whoever is programming the back end of the system?

Not significantly so, I wouldn't think. Just add a couple lines of code to compare the actual travel time to the travel time at the legal speed limit and display whichever is greater.

[vtk]

The signs use the actual speed of traffic, not the speed limit. Having a travel time sign that shows you the time at the speed limit would be pointless, since it doesn't matter what the speed limit is if the road is congested.

In/around Seattle, if the road is congested, then yes, they use the actual speed of traffic, but they always "max out" at the speed limit. The sign in South Everett 26 miles north of Seattle frequently shows travel times of more than 26 minutes, but never less than 26 minutes.

The examples in the part of my post you cut out clearly show that Massachusetts does not max them out at the speed limit. Seems much more useful than the WSDOT ones.

Also, wouldn't having the times max out at the speed limit require more work on the part of whoever is programming the back end of the system?

Assuming for the sake of argument the practice of rounding the minutes figure down, 3 miles in "2" minutes could be any speed above 60 MPH but not more than 90 MPH.  For 6 miles in "4" minutes, the speed used in the calculation would have to be more than 72 MPH, which indeed makes for compelling evidence that the signs in Massachusetts do not adjust travel times to reflect the speed limit.

As for the programming, imposing a minimum on the displayed travel time is trivial.  The minimum amount of time it takes to drive from point A to point B while obeying the speed limit can be precomputed.  (Which is more work for someone in the setup process, but not a programming issue.)  Then, the bit of programming that controls the sign message needs only to look up that stored value, compare it to the travel time calculated from speed sensors, and use the greater value in its output.  I'm fairly sure the travel time signs in Cincinnati and Columbus do this.

[hotdogPi]

I have always seen 16 miles 14 minutes, never 16 and 13, 16 and 15, or 16 and 16. (Of course, when there is traffic, it will change.) Same with 13 miles 12 minutes: never 13 and 11.

[roadman65]

I love when a sudden traffic jam occurs and local road agencies have not gotten a chance to update the information.  Therefore you are sitting in stopped traffic and it giving you great timing to a place you know is impossible to achieve.

[bob7374]

Here's a blog entry from last week that attempts to explain the logic behind what appears on MassDOT's VMSs:
http://www.boston.com/community/blogs/roads_and_rails/2013/08/behind_screens_vms_downtown_detours.html

[jeffandnicole]

Here's a blog entry from last week that attempts to explain the logic behind what appears on MassDOT's VMSs:
http://www.boston.com/community/blogs/roads_and_rails/2013/08/behind_screens_vms_downtown_detours.html

Last year a multi-screen message warned of construction. I transcribed from memory later as "blah blah blah construction ahead masspike blah blah blah 2 left lanes closed". Could have been one screen: "left lanes closed 3 miles ahead." If only they had a brain.

Says the guy that can't remember the message but used it for his ranting example.

[NE2]

Says the guy that can't remember the message but used it for his ranting example.

Says the guy who apparently missed the point.

[Billy F 1988]

Says the guy that can't remember the message but used it for his ranting example.

Says the guy who apparently missed the point...

...by a long shot.

Anyways...I have to wonder what DoT pays certain people to calibrate and program changeable message signs. I just hope Montana DoT doesn't make any of these apparent mistakes. I can't say they haven't, but I can't be sure if there have been times where such cases arisen.

[Scott5114]

Maybe someone has already done this, but wouldn't it be possible to have a VMS that essentially worked like a giant e-ink screen–like you have on a Kindle? The sheeting behind could be retroreflective and require no backlighting, and since electricity is only needed to change the display, the e-ink display could be almost entirely non-powered. And of course such a screen would also be able to reproduce perfect FHWA alphabets, route shields, and diagrammatics. It would be a quantum leap ahead of our current VMSes–which are about as technically advanced as the game board on 1970s-era Family Feud.

Perhaps it's possible but just too expensive at this time.

Funny you should say that, because the game board on 1970s era Family Feud worked in essentially the way you describe. Each pixel was a magnetized dot that was black on one side and yellow on the other. Electromagnets refreshed the display. The only difference is than an "e-ink" display would have smaller pixels.

[ET21]

The worst?

How about IDOT's campaign to show you how many people have dies on Illinois roads this year so far:

763
TRAFFIC DEATHS
THIS YEAR

It's stupid and morbid, IMHO.  Of course, I'm rooting for it to pass 1,000. 

Plus they put it during rush hour, when I would be more concerned with travel times than this 

[Kacie Jane]

Seems much more useful than the WSDOT ones.

My logic is this.  If traffic is light enough that you could get from S. Everett to Seattle in 26 minutes, then you could probably also get there in 22 minutes if you so desired.  If you look at it not so much as a strict time measurement, but as a measure of congestion, then the case where you can go 26 miles in 26 minutes represents 0 congestion, and depicting cases of <0 congestion is a bit daft.

(To put it another way, say my personal average speed in ideal conditions on that section of highway were 65 mph, thus taking me 24 minutes to reach my destination.  If the screen reads 26 minutes, that means traffic is light enough that I could probably still get there in 24 minutes with only a minimal amount of weaving, if any.  If the screen reads 22 minutes, I'm still going to take 24 minutes to get there -- keeping to the right lane, of course.  The ability to show speeds faster than the speed limit doesn't actually provide any additional usefulness when it comes to communicating congestion levels.)

[deathtopumpkins]

Seems much more useful than the WSDOT ones.

My logic is this.  If traffic is light enough that you could get from S. Everett to Seattle in 26 minutes, then you could probably also get there in 22 minutes if you so desired.  If you look at it not so much as a strict time measurement, but as a measure of congestion, then the case where you can go 26 miles in 26 minutes represents 0 congestion, and depicting cases of <0 congestion is a bit daft.

(To put it another way, say my personal average speed in ideal conditions on that section of highway were 65 mph, thus taking me 24 minutes to reach my destination.  If the screen reads 26 minutes, that means traffic is light enough that I could probably still get there in 24 minutes with only a minimal amount of weaving, if any.  If the screen reads 22 minutes, I'm still going to take 24 minutes to get there -- keeping to the right lane, of course.  The ability to show speeds faster than the speed limit doesn't actually provide any additional usefulness when it comes to communicating congestion levels.)

I disagree - to me, being unable to do 5-10 over the speed limit counts as congestion. There is a difference to me between puttering along in a mass of cars barely doing 65 and having an open road to fly along at 75. In my case the latter is 0 congestion, and the former is minor congestion, but still worth of reporting.

The problem with your argument is that you're assuming the speed limit to be the average speed in ideal conditions, which it rarely ever is.

[oscar]

Here's one, from May 2012 at one end of a work zone in Virginia on US 221 between Bedford and Lynchburg:



Maybe unusual candor from someone on the construction crew (though we always knew what they were best at).  But a similar VMS at the other end of the work zone ("EXCEPT DELAY") suggests it was just someone who can't spell.

[agentsteel53]

(To put it another way, say my personal average speed in ideal conditions on that section of highway were 65 mph, thus taking me 24 minutes to reach my destination.  If the screen reads 26 minutes, that means traffic is light enough that I could probably still get there in 24 minutes with only a minimal amount of weaving, if any.  If the screen reads 22 minutes, I'm still going to take 24 minutes to get there -- keeping to the right lane, of course.  The ability to show speeds faster than the speed limit doesn't actually provide any additional usefulness when it comes to communicating congestion levels.)

to get from 26 to 24 under many circumstances would imply some weaving skills worthy of Mario Andretti.  as traffic levels increase, things go away in this order:

1) the ability to consistently go at the average speed
2) the average speed itself

[Kacie Jane]

I disagree - to me, being unable to do 5-10 over the speed limit counts as congestion.

Right.  But what I'm saying is that even if it's reporting what I'm calling 0 congestion and an average speed of 60 mph, you can probably still do 5-10 over the speed limit (but probably not 15-20).  If it were a rare case where the 26 meant exactly 26, then yeah, there are probably a lot of cars on the road, and there might be some of what you're calling "minor congestion" at some of the ramps, but the left lanes are probably more or less free-flowing (at least until the section between SR 520 and I-90).

The problem with your argument is that you're assuming the speed limit to be the average speed in ideal conditions, which it rarely ever is.

Not exactly, though I'm probably notorious at this point for expressing myself poorly.  My argument is that this is actually a pretty silly argument, because knowing Seattle traffic, it's probably pretty unlikely that the average speed is precisely 60 mph. (If the VMS were displaying a true 26, that probably means that it's free-flowing (speed > 60) up to a certain point, with a couple of miles of < 40 mph through downtown and/or the U-district.  And while Jake may be right re: Mario Andretti, I think once you get beyond 26, and not by very much, the weaving does become a non-issue.

[Alps]

Maybe someone has already done this, but wouldn't it be possible to have a VMS that essentially worked like a giant e-ink screen–like you have on a Kindle? The sheeting behind could be retroreflective and require no backlighting, and since electricity is only needed to change the display, the e-ink display could be almost entirely non-powered. And of course such a screen would also be able to reproduce perfect FHWA alphabets, route shields, and diagrammatics. It would be a quantum leap ahead of our current VMSes–which are about as technically advanced as the game board on 1970s-era Family Feud.

Perhaps it's possible but just too expensive at this time.

Problem is that you want these signs to be visible from far away, which means some part of the sign needs to be lit, which means you're still using power all the time.

[agentsteel53]

Problem is that you want these signs to be visible from far away, which means some part of the sign needs to be lit, which means you're still using power all the time.

why is this necessary?  if the background were retroreflective, then it would not be need to be lit, would it?  or am I missing something here?

[Alps]

Problem is that you want these signs to be visible from far away, which means some part of the sign needs to be lit, which means you're still using power all the time.

why is this necessary?  if the background were retroreflective, then it would not be need to be lit, would it?  or am I missing something here?

How do you have a retroreflective background with the letters changing on it? Also, the letters themselves wouldn't be retroreflective, and nothing's harder to read than black letters on a reflective background (ask NY and CT button copy).

[vtk]

Problem is that you want these signs to be visible from far away, which means some part of the sign needs to be lit, which means you're still using power all the time.

why is this necessary?  if the background were retroreflective, then it would not be need to be lit, would it?  or am I missing something here?

How do you have a retroreflective background with the letters changing on it? Also, the letters themselves wouldn't be retroreflective, and nothing's harder to read than black letters on a reflective background (ask NY and CT button copy).

The problem with NY and CT button copy, as I understand it – also a problem in Ohio sometimes – is that the letters are supposed to be white, but they're not as reflective as they're supposed to be, making them relatively dark.  Meanwhile, the background is very reflective, but it's supposed to be a dark color.  And the result is a poorly-reflective white against a too-reflective dark color, which turns out to be nearly the same brightness and thus there's not enough contrast to read the sign.  A sign that literally has black legend on a retroreflective (light-colored or white) background works quite well.

The talk in this thread about having a reflective background comes from the misconception that "e-ink" technology works like an LCD, where there's a static background which is selectively darkened by changing foreground elements.  E-ink doesn't work that way.  A giant LCD panel with a retroreflective background could work, but due to the polarizing nature of LCD displays, you cut the reflected light by at least half even in the parts of the display that are supposed to be white.  As for e-ink, that's really very similar to the Family Feud display described above, but the individual elements are microscopic, and many of these elements are addressed by the same logical pixel, even on high-density e-ink displays.  I think incorporating retroreflectivity into this technology would be difficult – and unnecessary. 

A VMS probably doesn't need pixels smaller than an inch; at 4 dots per inch, you could fairly accurately reproduce the FHWA fonts.  Manufacturing rotating pixels that are a retroreflective light color on one side and black on the other shouldn't be too hard.  Actually, I think there are one or two older VMS in Columbus that use technology like this, with pixels about 1 to 2 inch in size.  I suspect the expense of this display type would be significantly more for smaller pixels, possibly just because manufacturers aren't currently making them.  Columbus's newer VMS have light-emitting pixels (probably LEDs) at 1 inch or smaller, and I think it's a safe assumption that this was determined the most cost-effective technology to meet ODOT's needs at the time.

[briantroutman]

How do you have a retroreflective background with the letters changing on it? Also, the letters themselves wouldn't be retroreflective, and nothing's harder to read than black letters on a reflective background (ask NY and CT button copy).

The talk in this thread about having a reflective background comes from the misconception that "e-ink" technology works like an LCD...

OK perhaps I am mixing up a few technologies. Upon further review, I see that the e-ink particles have a light side and a dark side, and those sides are alternately charged (positive or negative). So changing the charge of the matrix behind the screen causes the particle to flip–dark or light depending on the polarity. That isn't exactly what I had envisioned.

I remember hearing about a similar but slightly different technology where rather than flipping heads or tails, the pixels would stand on end when a positive charge was applied–thereby allowing light to pass through–or lay flat and block the light when a negative charge was applied–sort of like a million microscopic shutters. In this case, a solid retroreflective sheet could be behind the pixel layer, acting almost exactly like any other retroreflective signage–just with pixels blocking the light instead of pigment.

If I recall correctly, like e-ink, this technology only needed to power applied to redraw the display. In either case, the low power requirements would merely be a side benefit. I think the primary advantage would be having a VMS that looked and behaved more like regular signage–not glowing at you like a scoreboard or TV screen.

[ztonyg]

The WORST of Changeable Message Signs was -- bar none -- the ones that M-DOT placed over many of the freeways in and around Downtown Detroit in the late 80's/early 90's:

They were all Black-on-Gray LCD signs -- imagine your local digital gas-pump readouts in an enlarged dot-,...er triangle/square-matrix format that was nearly unreadable with-or-without lighting, day or night.  And even if you could read the text, most of the time there was usually a section which was stuck in an on-or-off position. 

Worst.Sign.Technology.Ever.

I'm not sure I remember those signs in Michigan but I do remember these. These were everywhere in SE Michigan until about 10 - 11 years ago and didn't seem to be much better than the signs you mentioned:

https://goo.gl/maps/a2JESgvKgNvUSwXM8

https://goo.gl/maps/qsDU1UBvLPCmyMY79

https://goo.gl/maps/ao3zvqH9PB51cWQW7

https://goo.gl/maps/D6cS1kt2D6m3bX5c6

https://goo.gl/maps/81ewD3uDGPa4dFYJ7

https://goo.gl/maps/9jz1nNBgQDcA6GiMA

https://goo.gl/maps/daADPkQ7MDsxp997A

As you see in the photos, there are a number of pixels stuck "on" or "off" and didn't have a ton of backlighting to stand out.

[thenetwork]

The WORST of Changeable Message Signs was -- bar none -- the ones that M-DOT placed over many of the freeways in and around Downtown Detroit in the late 80's/early 90's:

They were all Black-on-Gray LCD signs -- imagine your local digital gas-pump readouts in an enlarged dot-,...er triangle/square-matrix format that was nearly unreadable with-or-without lighting, day or night.  And even if you could read the text, most of the time there was usually a section which was stuck in an on-or-off position. 

Worst.Sign.Technology.Ever.

I'm not sure I remember those signs in Michigan but I do remember these. These were everywhere in SE Michigan until about 10 - 11 years ago and didn't seem to be much better than the signs you mentioned:

https://goo.gl/maps/a2JESgvKgNvUSwXM8

https://goo.gl/maps/qsDU1UBvLPCmyMY79

https://goo.gl/maps/ao3zvqH9PB51cWQW7

https://goo.gl/maps/D6cS1kt2D6m3bX5c6

https://goo.gl/maps/81ewD3uDGPa4dFYJ7

https://goo.gl/maps/9jz1nNBgQDcA6GiMA

https://goo.gl/maps/daADPkQ7MDsxp997A

As you see in the photos, there are a number of pixels stuck "on" or "off" and didn't have a ton of backlighting to stand out.

Prior to those, weren't there LCD message boards around metro Detroit?

Black-On-Gray alpha-numeric characters are fine on a gas pump or digital watch, but on a huge overhead gantry,....