1. Lecture #11 Signal Coordination: Chapter 22

2. Objectives Factors affecting coordination Basic theory of signal coordination Application to arterial progression

3. Factors Affecting Coordination Benefits Purpose of signal system Factors lessening benefits Exceptions to the coordinated scheme

4. Concept: Maximize Progression By Adjusting Offsets 0 30 60 90 120 150 180 210 t1t1 Time (sec) t2t2 1 st Signal 2 nd Signal 3 rd Signal t3t3 Distance (ft) Note: Definitions of offset vary, but text convention is offset is t 2 – t 1 and t 3 – t 2

5. Benefits of Signal Coordination Stops and Delay Performance index: combining measures Cost =A X (total stops) + B X (total delay) What are some other benefits?

6. Engineering Options What type of system is it? Which movements will be progressed? What is the objective? What happens if you can not achieve the objective?

7. Factors Lessening Benefits Inadequate roadway capacity Side friction Complicated intersection timing plans Wide variability in traffic speeds Short signal spacing Heavy turn volumes {see figure 22-3}

8. Time Space Diagrams and Ideal Offsets What is an offset? What is an ideal offset?

9. 0 30 60 90 120 150 180 210 t1t1 Time (sec) t2t2 1 st Signal 2 nd Signal 3 rd Signal t3t3 Distance (ft)

10. One-Way Progression For one-way progression, what do you need to know to estimate ideal offsets? How do you construct a time-space diagram? Can specify offsets relative to one (master) intersection

11. 0 30 60 90 120 150 180 210 t1t1 Time (sec) t2t2 1 st Signal 2 nd Signal 3 rd Signal t3t3 Distance (ft)

12. Effect of Queued Vehicles Qnumber of vehicles queued per lane (veh/lane) Hdischarge headway of queued vehicle (sec/veh) Loss 1 loss time associated with vehicles starting from rest at the first downstream signal (sec) How do you determine the offset with queuing?

13. Different Types of Progression What are the different types of progression? – Simple – Forward – Flexible – Reverse – Simultaneous

14. Two-Way Progression Progression in one direction suffers Segment offsets t SB +t NB = nC Maximizing bandwidth – Popular – Limited

15. Two-Way Progression (Cont.) Simultaneous progression – Closely spaced intersections – Queue management Alternate progression – Uniform block length – 50:50 split Nthe number of blocks with simultaneous green How do you determine N?

16. 0 30 60 90 120 150 180 210 Time (sec) 1 st Signal 2 nd Signal 3 rd Signal Distance (ft) 1000 ft intersection spacing 2 lanes in each directions C = 60 sec w/ 50:50 split 4 th Signal 5 th Signal What is the progression speed? What is the nonstop volume? Working Line

17. Two-Way Progression (cont.) What about arterials with non-uniform intersection spacing?

18. 0 ½ C C 1½ C 2C 2½ C 3C 3½ C Time (sec) Distance (ft) Working Line

19. 0 ½ C C 1½ C 2C 2½ C 3C 3½ C Time (sec) Distance (ft) Working Line

20. A Signal Coordination Study Go to the field and ride through the system – Do you see unused green time at down stream signals? – Do you arrive at signals with standing queues? – Do you arrive on red? – Is the flow in the other direction significant? Sketch out network with flow patterns Which cycle length is most appropriate?

21. Oversaturated Conditions Removal of intersection blockage – Address root causes – Update signalization – Use novel signalization to reduce extent of congestion – Provide more space – Prohibitions vs enforcement vs resulting problems – Consider other options

22. Oversaturated Conditions Signal based remedies – Metering plans – Shorter cycle lengths – Equity offsets – Imbalanced split