Two Phase Signalized Intersection with High Volumes
In this case, we will be using the given volumes to find the optimal cycle length. If you have trouble with this case, use Case Study 1 as an example.
Movement |
NBLT |
NBTH |
NBRT |
SBLT |
SBTH |
SBRT |
Volume |
186 |
1275 |
66 |
31 |
374 |
50 |
Movement |
EBLT |
EBTH |
EBRT |
WBLT |
WBTH |
WBRT |
Volume |
152 |
649 |
80 |
75 |
133 |
131 |
| Desired v/c Ratio ((v/c)c) | 0.85 | Headway (h) | 2 sec |
| Peak Hour Factor | 0.90 | Lost Time per phase (tl) | 3 sec |
| Pedestrian Volumes | 200 per hour | Heavy Vehicles | 8% |
Worksheet:
For this case study, we have an Excel worksheet which you may use or print out. If you decide to use Excel, be sure to right-click the link and "save target as" or "save link as." If you are asked for a password, just press escape.
Step 1: Phasing Plan
Check for protected left turn phasing .
Step 2: Volume Adjustment
Conversion of all volumes to tcus. The equivalent factors may be found here.
Step 3: Critical Volume
Step 4: Cycle length
Step 5: Green Split
Check your green split values for Phase A and Phase B.
Step 6: Signal Timing Plan
Signal Timing Plan includes the phasing plan, cycle length, and green splits.
Step 7: NEMA Phasing
In order to input the timing plan into the controller, you must assign NEMA phase numbers to the phases (convert Phase A to NEMA Phase #, and so on). The link above should help with this.
Step 8: Controller Settings
Follow all of the instructions given, especially the CLEAR and RESTART to ensure that your settings are properly implemented. Use the default all-red and yellow values (2 and 3 respectively).
Step 9: CID Configuration
Download (if you haven't already) and open Case Study 2.trf
The turn types for this case study should all be set to "Perm".
Step 10: Traffic Simulation
Use TSIS to open "NIATT Signal Timing Project - Case Study 2 - Simulation.trf"
Step 11: Execute Trafvu
This program allows you to view an animation of your signal. Do not start the animation until the simulation has reached equilibrium - usually about three minutes.
Continue on to Case Study 3.