What is the smallest number of signal heads required to control a single movement?

What is the smallest number of signal heads required to control a single movement?

• A. 1
• B. 4
• C. 2
• D. 3

Answer: (C)

When signaling a single movement, drivers must clearly see the indication from all lanes that could execute that movement. A single signal head can be blocked from view by vehicles or not easily seen by drivers in different lanes. Providing two signal heads for the same movement ensures visibility to all approaching drivers and keeps the indication clear throughout the cycle. So, the minimum arrangement to control a single movement is two signal heads; more heads may be added for additional lanes or visibility, but two is the smallest practical number.

When signaling a single movement, drivers must clearly see the indication from all lanes that could execute that movement. A single signal head can be blocked from view by vehicles or not easily seen by drivers in different lanes. Providing two signal heads for the same movement ensures visibility to all approaching drivers and keeps the indication clear throughout the cycle. So, the minimum arrangement to control a single movement is two signal heads; more heads may be added for additional lanes or visibility, but two is the smallest practical number.