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 head besides the one on the mast arm?  I have feeling that Caltrans just ignored the 40 degree angle requirement.  

 

Answer:  It sounds like you have looked at Figure 4D-2 in the California MUTCD (see http://www.dot.ca.gov/hq/traffops/signtech/mutcdsupp/ca_mutcd.htm).  It shows the 20-degree visibility cone (40-degrees total, as you mention). 



 

 

The answer to your question is found in the text on page 4D-18, paragraph D.4:

 

At least one and preferably both of the signal faces required by Item A in this Standard shall be located between two lines intersecting with the center of the approach at a point 3 m (10 ft) behind the stop line, one making an angle of approximately 20 degrees to the right of the center of the approach extended, and the other making an angle of approximately 20 degrees to the left of the center of the approach extended (see Figure 4D-2)