[Step 3] Adding Signal Heads
Signal heads, like stop signs, are placed in a lane and force a vehicle to decelerate to standstill condition while showing red. However, unlike a stop sign, a signal head, while showing red, will not allow vehicles to cross. Once the signal head shows green, vehicles may accelerate back to their desired speed.
In Vissim, a signal head works as both a signal head and stop bar in the field; therefore, it is important to place signal heads at the stop bar location. Follow the steps below to place a signal head in Vissim:
1) Turn on “Background maps” by clicking on the globe icon () in the network editor window and change the network display to wireframe mode (). This way, you can see the background map along with the skeleton of your network.
2) Click “Signal Heads” in the network objects window as shown in the figure to be in signal head insert mode.
3) Zoom in to the location where the new signal head will be placed.
4) Left click to select link or connector where signal head will be placed.
5) Press <CTRL> + Right click to place the signal head and Signal Head window will open as shown below.
6) Define the following data for this signal head:
SC and SG that this signal head will need to be connected to.
Display of the signal head during a simulation run including circular, left arrow, right arrow, and invisible.
Or Signal group – SC
Signal group: secondary SG connected to this signal head. If this option is selected, this signal head will display green when either primary or secondary SGs are showing green or it will show yellow when either (or both) of them are showing yellow. Unlike “overlap SG”, it will not display green automatically when it is transitioning in between primary and secondary SGs and show yellow when needed.
Vehicle classes that will obey the signal display at this signal head. If there will be any vehicle classes that will ignore this signal head, you should unselect “All vehicle types” and select desired vehicle classes.
Exercise (Download Example Files)
1) Open “Step_3_Add_Signal_Head” folder and load “Stringfellow_Rd_Step_3.inpx” file.
2) Go to “Signal Controllers” window and select “SC 4: Stringfellow Rd @ Fair Lakes Pkwy”.
3) Right click on row selected above and select “Zoom” in the context menu to zoom into the study intersection.
4) Update network display as needed. It is beneficial to switch to “Wireframe mode” (<CTRL> + A) and turn on labels for the signal head object and select signal group attribute to show SG numbers on the network editor as shown in the example file.
5) In addition to a few signal heads which are already placed, complete signal head settings along Stringfellow Road (N-S corridor) for the following movements:
- NBL: SG 1
- NBT & NBR: SG 6
- SBL: SG5
- SBT & SBR: SG2
- Crosswalk across EB approach: SG102
- Crosswalk across WB approach: SG106
6) Click “Save” icon and “Run” simulation and observe.