1. Lecture #15 Actuated Signals: Chapter 19

2. Objectives Understand the benefits of actuated signals Understand the basic parameters Application in a coordinated setting

3. Actuated Signal Parameters Minimum green Allowable gap Vehicle Extension Maximum green Recall switch Others Time Actuations

4. Calculating Minimum Green Time Detector setback, d Entire distance between detector and stop bar is occupied In what situations might you want to use this method? d Detector

5. Passage Time and Allowable Gaps What is a reasonable time for an allowable gap? – What would happen if it was too short (long)? How does the need for a reasonable allowable gap affect the passage time? How do allowable gap and passage time relate to vehicle extensions?

6. Determining Detector Setbacks given a desired minimum green – use equation 19-1 and solve for d: d = 10G min - 40 given allowable gap (3 to 4 seconds) – d = 1.468S(allowable gap)[19-4 and 5]

7. Application What detector setback would you recommend at the SB approach on Line Street? What minimum green would you recommend for the SB TH ? What minimum green would you recommend for the SB LT?

8. Maximum Green Time Fixed time phase splits – Use lane group values – Multiply by a factor (1.25 to 1.5) What if it is too short (i.e., less than calculated minimum green)? – Set to minimum – Use engineering judgment based on traffic patterns

9. Maximum Green Time (Question) How would you set up maximum green times for the 3 rd Street and Jackson signal?