Browsing Archive: October, 2009

When do traffic signals get installed?

Posted by Steve Fitzsimons on Friday, October 30, 2009, In : For the General Public 
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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Wipers on? Headlights on!

Posted by Steve Fitzsimons on Wednesday, October 14, 2009, In : For the General Public 
Question:  People were flashing their headlights at me all day yesterday.  Why?  

Answer:  You may have been driving in the rain without your headlights on.  California has a somewhat new law (passed in July 2005) that requires drivers to have their headlights on when weather is wet enough for use of your wipers.  The justification is simple, a moving car is easier to see when its headlights are on.  In wet, foggy, or misty weather, visibility is less than it is on a clear day.  Compensate for...
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Need more interchange ramps

Posted by Steve Fitzsimons on Tuesday, October 6, 2009, In : For the General Public 

Question:  Freeway access to Valley Fair Mall in San Jose is so bad I never shop there.  Why can’t someone build new ramps from northbound I-280 to Winchester Boulevard? 

Answer:  The brief answer is that the on-ramps to northbound I-280 from I-880 would be too close to these new off-ramps and create a dangerous weave pattern in the traffic.  Note that in the diagram below the traffic streams from A to D and from B to C have to cross within the distance labeled as the Weaving Area.  As lon...


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Night vision and Streetlights

Posted by Steve Fitzsimons on Monday, October 5, 2009, In : For Streetlight designers 
Question:  I'm interested in LED streetlight technology and have read about scotopic light measurements.  What can you tell me about that term?

Answer:  LED street lights seem to be the new rage-everyone is interested and there is a plethora of products to choose from as well as more than enough salespeople to keep us all busy.  According to the most recent Department of Energy independent testing less than half measure up to the manufacturer’s claims.  One important advantage they tout is t...
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About Us


Steve Fitzsimons If you would like to ask a question about driving rules, traffic signals or street lights, send your questions to: SFitzsimons@W-Trans.com or call 650-314-8313. Steve Fitzsimons is a professional Civil Engineer and Traffic Engineer in California. He is a principal at W-Trans. Find out more about W-Trans at www.w-trans.com **** If you need a traffic signal design or review, W-Trans is available for hire. If you are an electrical contractor, W-Trans is available for hire to prepare timing plans or traffic control plans.

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