Variable speed limit signs in Georgia deemed unreliable

[afguy]

It was billed as a cost-effective and innovative way to address traffic but after nearly a year-and-a-half and about $4 million later, some the signs apparently aren't communicating with each other, and that's causing all sorts of confusion for commuters.

Natalie Dale with the Georgia Department of Transportation says of the 176 signs that were installed, 19 of them aren't working correctly because of a wiring glitch. That can be confusing for drivers when one side of the road reads 35 miles-per-hour while the other side reads 65 miles-per-hour.

"The signs harmonize traffic and if there's an accident ahead of you, there are pavement sensors that tell you the traffic ahead is slowing down," said Dale. " We are focused on getting the signs fixed by turning ones off that aren't working."

St. Louis, Missouri, one of the first cities to begin using the variable speed limit signs, has already given up. City officials were too skeptical of the signs and law enforcement agencies weren't excited about them either.

Because of that, the city took down the signs and the program was dismantled.

But don't expect that to happen in Atlanta. GDOT says they are committed to new and innovative concepts and are working diligently to get the signs fixed.



Read more: http://www.cbs46.com/story/31645058/variable-speed-limit-signs-in-georgia-unreliable#ixzz4500t7VEZ

http://www.cbs46.com/story/31645058/variable-speed-limit-signs-in-georgia-unreliable

[jeffandnicole]

It was billed as a cost-effective and innovative way to address traffic but after nearly a year-and-a-half and about $4 million later, some the signs apparently aren't communicating with each other, and that's causing all sorts of confusion for commuters.

Natalie Dale with the Georgia Department of Transportation says of the 176 signs that were installed, 19 of them aren't working correctly because of a wiring glitch. That can be confusing for drivers when one side of the road reads 35 miles-per-hour while the other side reads 65 miles-per-hour.

"The signs harmonize traffic and if there's an accident ahead of you, there are pavement sensors that tell you the traffic ahead is slowing down," said Dale. " We are focused on getting the signs fixed by turning ones off that aren't working."

St. Louis, Missouri, one of the first cities to begin using the variable speed limit signs, has already given up. City officials were too skeptical of the signs and law enforcement agencies weren't excited about them either.

Because of that, the city took down the signs and the program was dismantled.

But don't expect that to happen in Atlanta. GDOT says they are committed to new and innovative concepts and are working diligently to get the signs fixed.



Read more: http://www.cbs46.com/story/31645058/variable-speed-limit-signs-in-georgia-unreliable#ixzz4500t7VEZ

http://www.cbs46.com/story/31645058/variable-speed-limit-signs-in-georgia-unreliable

Duh.  You multiple the two. 

Speed limit is 2275 mph.  And officer, I was only doing 80.

[jakeroot]

Nevermind the dozens of other cities that use variable limits without issue. I'm guessing St Louis was the only city that fit the story's narrative.

Seattle's variable limits, which are slowly blanketing every freeway, seem to be working well. Unlike most cities, WSDOT puts the limit over each lane, versus just on the edge. Often times, the HOV lane has a different limit than the GP lanes. This setup also allows for rolling lane closures, helping for when an incident blocks a lane. Red X's and yellow arrows indicate to vehicles which lanes are closed, and which lanes need to merge. When the variable limits aren't needed, the overhead VMS's are switched off, and the side-mounted VMS's are turned on, and display the standard urban limit.

[davewiecking]

Are the ones in Seattle set by humans? The CBS46 report mentioned the use of pavement sensors, making it seem that the Atlanta system is automatic. Then again, the interviewee said the problem was a wireless glitch, but the text says wiring glitch, so who knows... I'm not sure the Atlanta system is supposed to have different speeds for the different lanes, but certainly the Seattle sign-per-lane setup is the way to go if that's to be the case.

[jakeroot]

Are the ones in Seattle set by humans? The CBS46 report mentioned the use of pavement sensors, making it seem that the Atlanta system is automatic.

The limits can be adjusted manually, but they are primarily adjusted by computers:

Traffic sensors along the roadway collect vehicle speeds, congestion information and traffic flow rates. This information is continuously relayed back to the WSDOT's Traffic Management Center in Shoreline and analyzed by computers. When circumstances that would benefit from lowered speed limits–like congestion–are identified, the computer reduces speeds incrementally to gradually reduce the approaching flow of traffic to the congested area.

The lowest displayable limit is 40 mph.

Then again, the interviewee said the problem was a wireless glitch, but the text says wiring glitch, so who knows... I'm not sure the Atlanta system is supposed to have different speeds for the different lanes, but certainly the Seattle sign-per-lane setup is the way to go if that's to be the case.

IMO, the per-lane setup should be used on freeways with three or more lanes. The VSL style employed by WSDOT works well because the signs are impossible to miss. The kind employed by GADOT are rather small, shoulder-based setups that can easily be missed by center lanes. When drivers have a hard time seeing the sign, or simply don't notice the sign at all, the whole point of variable speed limits is lost.

[Brian556]

quote from jakeroot:

IMO, the per-lane setup should be used on freeways with three or more lanes. The VSL style employed by WSDOT works well because the signs are impossible to miss. The kind employed by GADOT are rather small, shoulder-based setups that can easily be missed by center lanes. When drivers have a hard time seeing the sign, or simply don't notice the sign at all, the whole point of variable speed limits is lost.

Excellent point. Many people, including traffic engineers, often falsey believe that right-side only signage is effective for multiple lanes. They often completely forget that it can be obscured by trucks. This doesn't just go for speed limit signs. This includes stop signs on undivided multilane streets

[lordsutch]

quote from jakeroot:
Excellent point. Many people, including traffic engineers, often falsey believe that right-side only signage is effective for multiple lanes. They often completely forget that it can be obscured by trucks. This doesn't just go for speed limit signs. This includes stop signs on undivided multilane streets

The variable speed limit signs on 285 are consistently installed on both the median and the right shoulder (visible in the still photo where the two signs disagree), and are fairly well elevated so they're unlikely to be obscured throughout the viewing distance, particularly since trucks are banned from the inner two lanes of 285.

[jakeroot]

Excellent point. Many people, including traffic engineers, often falsely believe that right-side only signage is effective for multiple lanes. They often completely forget that it can be obscured by trucks. This doesn't just go for speed limit signs. This includes stop signs on undivided multilane streets

The variable speed limit signs on 285 are consistently installed on both the median and the right shoulder (visible in the still photo where the two signs disagree), and are fairly well elevated so they're unlikely to be obscured throughout the viewing distance, particularly since trucks are banned from the inner two lanes of 285.

That doesn't mean that the side-only variable speed signs are suddenly perfect. I'm still pretty sure that the per-lane style, which WSDOT lifted from England's M42, is preferable with three or more lanes, simply because each lane has an equal chance of seeing the sign, rather than inner lanes having a pretty good chance, and outside lanes having a great chance.

[Jardine]

I can't imagine variable speed limits and differing speed limits in different lanes ever working in Omaha NE, and particularly in Sarpy County.

REQUIRING Nebraska motorists to pay attention to such things, and then understand what they mean and then obey    what is indicated is simply asking too much.

[Tom958]

I always thought they were a dumb idea. That said, I'm also getting the idea that GDOT is running into too many problems with its contractors. The Jimmy Carter DDI project took way too long, and the signals that were meant to control the dynamic lane running north from there were never installed. Seriously, the poles are there with wires sticking out of a hole ready for signals. And not long ago GDOT announced that they'd be putting signals on the 400 shoulder lanes, too. Then there's that screwed up APL that GDOT told me they'd direct their contractor to fix, and they actually made it worse. Gee, I dunno. And they're heading into a $10 billion construction program. Could be trouble.

[jeffandnicole]

There should be dozens of not hundreds of contractors, all of which specialize in their own area.  And then there's subcontractors whom the contractor uses. One would think the GDOT can throw them into a penalty box of sorts if they keep screwing up or missing deadlines.  Small stuff, like a US route sign rather than a Georgia route sign...no.  Large stuff, like indicating wrong lanes to be in which can cause confusion and accidents and failure to complete work? Yes.  But, they also have to figure out where the fault lies.  If GDOT designed something wrong, that's not the fault of the contractors.