Question:  How do the radio stations and TV stations know when there are traffic jams? Are there sensors in the street itself? Do they all go to websites where all of the cameras we see on the signal lights are coordinated and the information goes to one place? Is there one centralized place where all of these people go to for their information? Do they have to call or go to all the different websites?  Is it true what you see on TV or in the movies how people can hack into one place and see ...

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Question:  I just saw an article about solar roadways, where the asphalt pavement is replaced by solar panels.  The inventor claims if every highway were repaved with solar panels, it would generate enough power for the entire country.  http://www.gizmag.com/solar-panel-roads/12780/

Answer:  This topic is a bit beyond the scope of this blog, but I'll post it because it is such an exciting sounding idea.  It appears there is a lot of materials science research to be done.  The article does not ...
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Question:  I have two new signal systems about 500’ apart and speed limit is 30mph.  I worried about there would be visibility conflict between these two signals.  So, in what situation the louvered signal head is required?

 Answer:  The issue with closely spaced intersections is that the driver wating at the stop bar of the first one might see a green at the second one and start driving, even when the closer signal display is still red.  The Caltrans traffic manual had a guideline to rest...

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Question:  My City has recently installed a new traffic signal.  There is a curve in the southbound approach that limits the visibility of the signal heads.  How do I know if I need a Supplemental head or not?    

 

Answer:  Chapter 4 of the California MUTCD has your guidance.  First determine your travel speed on the approach.  Then look up the minimum visibility requirement in Table 4D-1 of the CA MUTCD http://www.dot.ca.gov/hq/traffops/signtech/mutcdsupp/pdf/camutcd/CAMUTCD-Part4.pdf  . ...

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