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Basic Signal Timing Background

To understand the basics of signal timing you should understand the following concepts.

• Signal Operations

  • Phase Assignment

  • Definitions

  • Phase Diagrams

• Calculations

  • Headway (h) and Saturation Flow Rate (S)

  • Lost Time (t_L)

  • Critical Volume

  • v/c Ratio

  • Peak Hour Factor (PHF)

  • Cycle Length Calculation (C)

  • Capacity

• Overlap Phasing

  • Overlap Definitions

  • Overlap Calculations

Since this is a lot of material to cover, we have split it into three separate pages.  On the Signal Operations page we will discuss intersection phasing and various terms related to signalized operations. On the Calculations page, we will discuss the calculations and assumptions involved in setting signal timing. After you have reviewed the first two pages, you will be ready for case studies 1, 2, and 3. Overlap Phasing goes into more detail about how to handle protected left turns, with examples in case studies 4, 5, and 6.