Browsing Archive: July, 2009

Left Turn Signal Head Placement

Posted by Steve Fitzsimons on Thursday, July 16, 2009, In : For Traffic Signal Designers 

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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Slower Traffic Keep Right

Posted by Steve Fitzsimons on Tuesday, July 14, 2009, In : For the General Public 

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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Traffic signal basics

Posted by Steve Fitzsimons on Friday, July 10, 2009, In : For the General Public 

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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Mast Arm Mounting

Posted by Steve Fitzsimons on Friday, July 10, 2009, In : For Traffic Signal Designers 

Question:  In a recent signal design, I needed the mast arm signal raised a bit higher for clearance and suggested connecting the MAS mount between the yellow and green indications.  A reviewer told me this is not a good idea, and I’m hoping for a more detailed reason why not. 

Answer:  Caltrans Standard Plan ES-4D (http://www.dot.ca.gov/hq/esc/oe/project_plans/highway_plans/stdplans_US-customary-units_06/viewable_pdf/rspes-04d.pdf) shows the MAS mounting but doesn’t really explain how th...


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Help for pedestrians

Posted by Steve Fitzsimons on Wednesday, July 1, 2009, In : For Traffic Signal Designers 

Question:  I’m designing a traffic signal at an intersection with a heavy right turn out of a minor street, plus a very low volume pedestrian crossing that is in conflict with the right turn move.  I’m thinking of having a right turn arrow that will display a red when there are pedestrians, and will show a green when there are no pedestrians.  The controller is a 170 with McCain software.  Here’s a sketch of what I’m wanting to do, how do I make it work? 

 

Answer:  McCain software h...


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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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