Freeway

Freeway

Main Input Screen The main input screen (see Figures below) is where the roadway geometry is specified. This is done by adding segments/links where you can set the length, initial angle, free-flow speed, grade, and so on. You can insert a basic segment, on-ramp segment, or off-ramp segment with the toolbar buttons above the segment table. Click ‘Delete Link’ to delete the currently selected segment. The segment characteristics assume an east-to-west or north-to-south direction of entry.





Segment Input Fields Most of the input fields for the freeway facility are the same as for the two-lane highway facility. The only differences are that the freeway has an input for the number of lanes for the segment and does not include inputs for a passing lane.

Detectors The detector input screen for the freeway facility only accommodates one direction. To set detectors on a segment click on ‘Set’ under ‘Set Detector(s)’ to open the Detectors dialogue box (see Figure below).

Entering Traffic Data For a freeway facility, traffic enters at the beginning of the mainline and from each on-ramp. The traffic data entry dialog (similar to the one for two-lane highways, but for just one direction) can be accessed for each facility entry point by pressing the ‘Set’ button under the ‘Traffic Data’ column. This button will be highlighted in yellow for the segments for which entering traffic data can be specified.

Exiting Traffic Data For off-ramp segments, the exiting percentage of traffic needs to be specified. This entry is accessed in the same way as for the entering traffic data.

To save your created network and traffic data to disk, see Section File Management. To run the simulation, see Section Running the Simulation. Following successful completion of the simulation, you can view the results in the animation window (see Section Animation).

Signalized Intersection (Template)

Main Input Screen The main input screen (see Figure below) is where the roadway and traffic data are specified.

Roadway Data
 * Geometric Template: one of two intersection configurations can be selected by clicking on the dropdown box under ‘Geometric Template’. Template 1 consists of two thru lanes only per approach. Template 2 consists of two thru lanes a left-turn bay per approach. It should be noted that while a signal phasing pattern other than “split phasing” can be simulated with template 1, the results will obviously not be sensible and may even cause the program to crash during the simulation.
 * The posted speed limit for the E/W and N/S approaches are also specified in this section. These values are used to set the mean vehicle desired speed. The minimum value is 20 mi/h and the maximum value is 45 mi/h.

Traffic Data Enter the traffic demand, in units of veh/h, for each of the movements in this section.
 * The vehicle type distribution is also specified in this section. The signal module of SwashSim is currently limited to passenger cars/trucks. However, it does consider an equal percentage of 11 different passenger vehicles:
 * 2006 Honda Civic Si
 * 2005 Mazda 6
 * 2008 Chevrolet Impala LS
 * 2004 Pontiac Grand Am GT
 * 2001 Volvo S40
 * 2009 Honda Civic
 * 1998 Buick Century
 * 2002 Chevrolet Silverado
 * 2011 Ford F150
 * 1998 Chevrolet S10
 * 2004 Chevrolet Tahoe

Signal Phasing and Timing Inputs Pressing the ‘Set Phasing & Timing’ button on the main inputs screen will load the ‘Signal Phasing and Timing Inputs' screen (see Figure below). To add a timing stage, press the “Add Timing Stage” button. This will highlight the next available Timing Stage box in yellow. To edit a Timing Stage, click the desired stage so that it is highlighted in yellow. Timing stages are used to specify the phases (1-8) that will move (i.e., receive green) simultaneously. To add a traffic movement to the timing stage, click on the desired movement arrow(s) in the ring/barrier diagram. To remove a movement, click on the corresponding arrow in the ring/barrier diagram. If movement is selected that conflicts with another movement in that timing stage, an error message will appear and the movement arrow will not be added to the timing stage. For each timing stage, the green, yellow, and all-red times need to be specified. To edit a timing interval, click on the appropriate table cell to highlight it in blue and type in the desired number. Press the ‘Tab’ or ‘Enter’ key to save edits. Note that the number in the left-most column corresponds to the timing stage number. The figure below shows an example timing stage plan. When the timing stage movements and corresponding interval times have been specified, the last step is to select ‘Create Signal Controller Phasing/Timing Plan’. This will generate a timing plan that is used by the dual-ring signal controller (see Figure below). If revisions are made to the timing stages and/or interval times, press the ‘Create Signal Controller Phasing/Timing Plan’ again to create a new signal controller timing plan. The last timing plan that is generated is the one that is stored in memory. The simulation program will continue to store this timing plan in memory for the duration of the current session. If you want to save the timing plan to disk, press the “Save To File” button. With this, the timing plan can be reopened in a different program session. After exiting the ‘Signal Phasing and Timing Inputs’ screen and successfully creating a timing plan, the main inputs screen will show ‘Loaded’ for the ‘Timing Plan Status’ (see Figure below).