From a friend.  Makes me wonder if this part of Ukraine has really thick fog or storms so heavy that normal traffic signal lights aren't visible.  Or maybe it's just something their tourist bureau wanted!  Festive, though!  


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One of my least favorite aspects of my profession is that traffic signals are just not attractive.  But the City of Breckenridge CO may have found a way.  Put up so many lights when decorating the town that the signal lights become part of the festivities!  
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The City of San Jose's website has a phone number and email address to report concerns about traffic signal timing.  I just called about an issue I have noticed at the intersection of Fruitdale Avenue and Meridian Avenue, and spoke with a very helpful man who told me the traffic signal coordination plan had recently been updated and the City is still fine tuning, and he would write up a work order to look into my concern.   If you have a question about traffic signal timing at an intersection...
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There are three observations I’d like to share with the folks in the professional community who are involved in traffic signal coordination, and I’m hoping to hear if others have noticed anything similar.  

First, when implementing coordination plans that have been developed with an optimization model, I often find ways to improve operations during the fine tuning step.  The last step of the process is to input the final timing settings back into the model and run it one last time to ge...

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Traffic adaptive systems are computer systems that coordinate traffic signals by continually monitoring traffic volumes and making updates to the coordination plan every few seconds.  The concept is intended to provide ideal traffic signal operations through a corridor with multiple traffic signals.  A dozen years ago there were very few adaptive systems deployed in the US, and these were mostly in large cities with very high volumes of traffic.  Now a large number of systems have been deploy...
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Question:  Some traffic signals in snow country with LED lamps are getting clogged with snow.  Are there any new products to address this problem? 

Answer:  The lower wattage of LED traffic signal heads compared to incandescent also means the lamps generate less heat.  This allows snow or ice to form on the head and sometimes block the display.  In at least one case in Wisconsin, it has become a legal issue.  See http://www.todaystmj4.com/news/local/79008352.html

McCain Traffic Supply has d...

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Question:  I travel the same route to work on the same streets and at approximately at the same time 5 days a week. So here it is a holiday week and yes, traffic is lighter but then that gets me into work earlier. Why is it sometimes left-hand signals will be quick and other times they TAKE FOREVER. Is it lighter traffic not triggering the signal or is it time of day?

Answer:  The easy part of your question is the very last.  A traffic signal detector, with very few exceptions, is binary.  Y...

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Question:  I’ve been told Caltrans recently issued new guidelines on accommodating bicycles at signalized intersections.  Where can I find the details?

Answer:  In August, 2009, Caltrans issued a Policy Directive about new requirements for bicycle detection at signalized intersections and new guidelines for traffic signal timing to accommodate bicycle travel speeds.  You can find the full document at http://www.dot.ca.gov/hq/traffops/signtech/signdel/policy/09-06.pdf.  The document describ...

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The quick answer is that traffic signals are installed when "an engineering study indicates that installing a traffic control signal will improve the overall safety and/or operation of the intersection."  In other words, when volumes and congestion get high enough, or when the number of correctable crashes exceeds a certain amount, a traffic signal will improve safety and operations.  

Many local agencies monitor unsignalized intersections on an annual basis, keeping track of traffic volumes a...
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Question:  Caltrans publishes traffic count data that is organized by Route number and post mile.  The database sometimes includes counts on either side of a cross street, labeled as “Back” and “Ahead”.  The Ahead data for one posting should match the Back data for the next one, but sometimes they don’t.  What number should be used when they don’t match? 

 

Answer:  Caltrans traffic data is available on their website at http://www.dot.ca.gov/hq/traffops/saferesr/trafdata/2000al...

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Question:  For left turn signal heads, we usually install it on the mast arm and the far side 1-b pole.  The MUTCD requires a 40 degree viewing angle from the left turn lane.  There are situations that the far side left turn signal head is outside the 40 degree angle zone due to the width of the street.  I know Caltrans doesn’t like to put the 1-b on the median too.  We required to have at least two signal heads for each moment.  So, what’s your opinion for the second left turn signal hea...

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Question:  Do slower moving cars need to keep right?

 

Answer:  Section 21654 of the California Vehicle Code says:  (a) Notwithstanding the prima facie speed limits, any vehicle proceeding upon a highway at a speed less than the normal speed of traffic moving in the same direction at such time shall be driven in the right-hand lane for traffic or as close as practicable to the right-hand edge or curb

 

The word “Notwithstanding” means that even if a driver is moving 70 mph in a posted 70...

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Question:  How does a traffic signal work and why don’t I get a green when I’m on a motorcycle?

 

Answer:  The short answer is traffic signals work just like a person would who is directing traffic.  First it “sees” a vehicle that needs a green, then it provides the green.  Most traffic signals “see” with detector loops that are buried in the pavement.  These loops detect masses of conductive metal.  They detect large masses, like cars or trucks, very well.  If properly installed...

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Question:  When gap extension is programmed, do cities generally use the detectors to have this signal timing setting, or do cities program the controllers to have this setting?

Answer:  I’m used to thinking in terms of Gap Reduction.  Gap Reduction is done entirely in the controller unit inputs.

Extension is a term that is usually applied to a detector input.  Extension can be done either in the Detector Sensor (the part that sits in the rack/shelf in the controller cabinet), if it is the ...

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trafficanswers.org was launched in June 2009 to provide two functions:

1. to serve as a resource to professional traffic designers in California
2. to direct average California drivers to the answers to life's driving questions

It is the brainchild of Steve Fitzsimons, PE, TE, a professional transportation engineer with nearly 30 years experience as a California Traffic Engineer.  Major support is provided by his coworkers at Republic ITS and W-Trans.  

Send your questions to Steve at SFitzsimons...
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