Traffic Sign and Signal Vocabulary

Backplate: a black "frame" around the signal.  By masking off part of the background, it draws attention to the signal.  Canada uses yellow backplates for a similar purpose.

 

Ball: Traffic signal lens that is visible as a solid circle and not masked off for an arrow.

 

Conflict Monitor: Built in check and balance system on a traffic signal controller that will put a signal into flashing mode if more than one directive is given at a time to a direction of travel (e.g.. red and yellow on simultaneously) or if the directives given to two different directions of travel would cause an accident (e.g. north and west bounds both having a green indicator) 

 

Crossbuck: the name given to the X shaped railroad crossing sign.  The "Rail Road" plate is always behind the "Crossing" plate.  

Traditionally, "Rail Road" runs from top left to lower right.  Instances of running the other way do exist but just don't look right. 

In Canada, the signs read "Railway Crossing".  

 


Doghouse Signal: A five lens signal that is arranged in a 2X2 configuration (two rows each of yellow and green) with a single red lens centered on top.  This is a compact version of a five lens straight line signal.  Usually for left hand turns, however, right hand doghouses have been seen but are rare.

Depending on the programming, the turn can be independent of or at the beginning or end of the straight line traffic movement. Programming can also be sensor or time of day driven.  

 

Electro-Magnetic Controller: Older style of timer for traffic signals.  Ran on a dedicated cycle.  Amount of time various roads had the green could not be adjusted between rush hour and non rush hour.

 

Electronic Controllers: Newer solid state controllers for signals.  Can adjust the length of green throughout the day.  Can also give the green only when a vehicle has been detected in the turn lane or on a quiet street waiting to cross a major thoroughfare. 

 

High Visibility Signal: Traffic signal made by 3M which can be configured or  "masked" so that only the intended lanes of traffic get a clear indication of the signal command.  Programmable Visibility Signals are often used in left turn lanes, complex intersections, lane control, distance limiting, skewed intersections, and bimodal indications
*Some areas use traditional signals with baffled lenses*

 

Microwave Detector: Vehicle detection system that works in a way not too much different than submarine sonar.

 



Protected Left Turn: Left turns are directed by a dedicated or doghouse signal.  When it gives the green arrow, oncoming traffic is stopped.

Michigan signals have a backlit LEFT or RIGHT signal, most other states use the standard LEFT TURN SIGNAL and RIGHT TURN SIGNAL signs (DOT numbers R10-10L and R10-10R, respectively)

 

Red Arrows : In Michigan, a turn is only allowed if the arrow is flashing and it is safe to turn.  In Florida, a turn is allowed on a solid (not flashing) right arrow but prohibited on a sold left arrow.  Of course, a NO TURN ON RED sign, if present, must be obeyed.

 

Sensor Loop: Wire buried in the pavement to detect vehicle presence and give a green signal as needed.  Works by induction.  How it works

 


A "Michigan-style" 4-Way

_-way: Number of signals on a cluster.  Michigan is known for having primarily 4 way signals at its intersections.  3 ways are on T intersections or where a one way street meets a two way street.  2 ways are where two one way streets cross.

The logo for my traffic signal area is a "Michigan-style" 3-way with 12 and 8 inch lenses.