CEE 764 – Fall 2010 Topic 3 Basic Signal Timing and Coordination Principles

CEE 764 – Fall 2010 Signal System Classification  Traditional Systems Closed-Loop (Field Master) Closed-Loop (Field Master) Centralized Computer Control Centralized Computer Control  Adaptive

CEE 764 – Fall 2010 Signal Timing Process Data Collection Signal Timing Development Field Implementation

CEE 764 – Fall 2010 Basic Terminology  Cycle  Phase Split  Phasing Sequence  Offset  Force-off

CEE 764 – Fall 2010 Cycle Length and Split  Cycle Length All signals must have a common cycle length to achieve coordination  Split Split = Green + Yellow + All-red

CEE 764 – Fall 2010 Signal Coordination Intersection #1 Intersection #2 East Bound

CEE 764 – Fall 2010 Offset  Offset is the time difference between two reference points  Offset must be specified by Phase Phase Begin/end phase Begin/end phase  Offset = 0 ~ cycle length

CEE 764 – Fall 2010 Offset ф 2,6 ф 2,5 ф 1,5 ф 4,8 ф 2,6 ф 1,5 ф 4,8 ф 3,7 Local zero When the local zero occurs at 40 sec of the master clock We say the Offset = 40 sec

CEE 764 – Fall 2010 Time-Space Diagram One-way Street 22 66 22 66 22 66 22 66 88 44 88 44 88 44 88 44 G=25 Y=5 R=30 G=35Y=5R=20 Time #1 #2 EB Band

CEE 764 – Fall 2010 Time-Space Diagram Two-way Street 22 66 22 66 22 66 22 66 88 44 88 44 88 44 88 44 G=25 Y=5 R=30 G=35Y=5R=20 Time #1 #2 EB Band WB Band

CEE 764 – Fall 2010 Question 1:  2 and  6 at intersection #1 turn to green at 60 sec,  2 and  6 at intersection #2 turn to green at 20 sec, what are the offset s at the two intersections, assuming the offset is referenced to the start of green of  2 and  6? Questions Question 2: Given the offsets number in Q1, what will the offsets be if the offsets are referenced to the end of green of  2 and  6? Question 3: If the travel speeds are different for the two directions, will it affect the above offset results?

CEE 764 – Fall 2010 Offset and Transition  Synch point/clock: the time all offsets are referenced to. It is also called Master Clock Zero. It is usually set at 12:00 – 3:00 a.m. when traffic is light. 12:00 a.m. (Master Zero) Local Zero Master Zero Offset

CEE 764 – Fall 2010 Example  If the Synch point is set at 3:00 a.m., for a signal operating at an 90-sec cycle and an offset of 40, what would be the master clock timer and the local clock timer at 11:20 a.m.?

CEE 764 – Fall 2010 Transition Methods  Transition occurrences  Plan change  Preemption  Pedestrian  Transition methods/algorithms  Dwell  Max Dwell  Add  Subtract  Shortway

CEE 764 – Fall 2010 Example

Offset and Transition 22 66 22 66 88 44 88 44 88 44 #1 #2 11 55 22 66 11 55 EB: 20 sec WB: 8 sec

CEE 764 – Fall 2010 Bandwidth (Dual LT Leading) 22 66 22 66 88 44 88 44 88 44 #1 #2 11 55 22 66 11 55 EB: 20 sec WB: 8 sec

CEE 764 – Fall 2010 Bandwidth - Adjusted (Dual LT Leading) 22 66 22 66 88 44 88 44 88 44 #1 #2 11 55 22 66 11 55 EB: 20 sec WB: 12 sec

CEE 764 – Fall 2010 Bandwidth - Initial (Lead/Lag) 22 66 22 66 88 44 88 44 88 44 #1 #2 11 55 22 66 11 55 EB: 20 sec WB: 12 sec

CEE 764 – Fall 2010 Bandwidth - Adjusted (Lead/Lag) 22 66 22 66 88 44 88 44 88 44 #1 #2 11 55 22 66 11 55 EB: 20 sec WB: 20 sec

CEE 764 – Fall 2010 MOEs  Bandwidth Concept (PASSER II) Bandwidth, seconds Bandwidth, seconds Bandwidth Efficiency = Bandwidth/Cycle Bandwidth Efficiency = Bandwidth/Cycle Attainability = Bandwidth/g min Attainability = Bandwidth/g min  System-Wide Delay (Synchro)  System-wide Stops and Delay (TRANSYT-7F)

CEE 764 – Fall 2010 Yellow Trap “Yellow trap” is a situation faced by a left-turn movement when the display of “yellow” occurs to both the left-turn phase and the adjacent through phase, but the opposing through is not terminating. (1) (2) (3) (4) (5)

CEE 764 – Fall 2010 Dallas phasing has louver that through vehicles cannot see

CEE 764 – Fall 2010 Left-turn phase about to end

CEE 764 – Fall 2010 Through movements move both directions. Left-turn yield to opposing through.

CEE 764 – Fall 2010 Yellow trap occurs when the leading left-turn sees yellow and thinks the opposing through phase will also end

CEE 764 – Fall 2010 Dallas phasing does not display yellow, and left-turn sees green ball and is supposed to still yield.

CEE 764 – Fall 2010 When left-turn sees yellow, the opposing phase also about to end

CEE 764 – Fall 2010 Main street phases end, side street phases begin

CEE 764 – Fall 2010 Yellow Trap Only the leading left-turn has the “yellow trap” with protected/permitted phasing Dallas Phasing solves the "yellow-trap" problem by holding a solid green indication. Louvers are used to shield the left-turn display so that the green display in the left-turn signal cannot be easily seen by thru drivers. When can a “yellow trap” occur with standard PPLT with left- turns leading or lagging?

CEE 764 – Fall 2010 Summary  What is “Yellow Trap” and when it occurs?  What is the main purpose of using “Lead-Lag” phasing? Can “Lead-Lag” phasing increase an intersection capacity?  What is the exception that a different cycle length can be used at an intersection while still maintaining coordination?  Offset  Bandwidth  Time-Space Diagram

CEE 764 – Fall 2010 Lab Exercise 1. Use the Synchro offset optimization (keep cycle length and splits unchanged) and answer the following questions: What are the phasing sequences at each intersection?What are the phasing sequences at each intersection? How are the offsets referenced and what are the offsets?How are the offsets referenced and what are the offsets? Examine the timing solution and indicate where stops may occur if driving on the main street both directions.Examine the timing solution and indicate where stops may occur if driving on the main street both directions. 2. Can you further improve the bandwidth by changing the phasing sequences from Synchro? Answer the same questions above. 3. Which intersection is controlling the bandwidth?  Use the Kietzke system (3 signals) to perform the following exercise.

CEE 764 – Fall 2010 Lab Exercise 1. Understand the existing timing sheets and compare with Synchro coding. 2. Use the Synchro offset optimization (keep cycle length and splits unchanged) and compare Synchro timing solution with the existing (bandwidth) 3. How was the phasing sequence changed at each signal? Can you further improve the bandwidth by changing the phasing sequences from Synchro? 4. Which intersection is controlling the bandwidth? 5. Try only with two intersections (Harmon and Tropicana) and see how the solution changes.  Use the Boulder Highway system (3 signals) to perform the following exercise.

CEE 764 – Fall 2010 Signal Timing Sheets (NextPhase) Boulder Hwy/Tropicana Intersection – Schedule of timing plans x – Information of a timing plan: cycle, split, offset, sequence x – Phasing sequence x – Phase data (min green, yellow, all-red etc.) Phase designation (direction/movement) and ring structure

CEE 764 – Fall 2010 WB = 36 sec EB = 16 sec Lead/Lag Phasing

CEE 764 – Fall 2010 WB = 45 sec EB = 16 sec