Two-Lane Highway

Two-Lane Highway

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. Click ‘Add New Link’ to add a new roadway segment, click ‘Insert New Link’ to add a new roadway segment above the current segment you have selected, click ‘Delete Link’ to delete the currently selected segment.

Segment Input Fields Links and their corresponding characteristics are specified for the west-to-east or north-to-south travel direction (considered ‘Direction 1’) and the inputs for the opposing travel direction (considered ‘Direction 2’) are automatically created by the program.

Upstream/Downstream Node ID Each two-lane highway segment has a beginning and ending node. The upstream and downstream node Id identifies the segments before and after the currently selected segment. The node Id values are automatically created. Note that link Id values are created by concatenating the upstream and downstream node values. For example, Link Id ‘12’ corresponds to the link that has upstream node Id ‘1’ and downstream node Id ‘2’. Link Id ‘21’ corresponds to the link that has upstream node Id ‘2’ and downstream node Id ‘1’. For the two-lane highway module, link 21 would be created automatically by the program, as the opposing direction to link 12.

X Coord Start/X Coord End and Y Coord Start/Y Coord End The starting and end coordinates for each segment. These values are automatically created, based on the length and orientation angle, and horizontal curve inputs.

Length For tangent segments, the link length is entered in this cell. For curved links, the link length will be based on the curve radius and central angle. Consequently, the length cell for a curved link will be colored gray, indicating that it cannot be edited directly. User input of length is restricted to integer values; however, the program may replace entered values with decimal values as a consequence of curved links and/or coordinate point adjustments.

Orientation Angle This input corresponds to a compass angle based on the direction of travel (see Figure below). For example, the segment angle would be set as follows for the given travel directions: After specifying the angle for the first segment, the other segment angles will be calculated by the program.
 * 0o for perfectly horizontal east-to-west travel
 * 180o for perfectly horizontal west-to-east travel
 * 90o for perfectly vertical south-to- north travel
 * 270o for perfectly vertical north-to-south travel.

Horizontal Curve Specific Inputs If the segment corresponds to a horizontal curve, select ‘Yes’ for “Is a Curve?”. If this is done, additional segment inputs will be enabled, specifically: superelevation, curve radius, central angle, and curve direction (this latter input corresponding to the general turning direction of the curve). Filling in the central angle and radius of the curve will automatically adjust the segment length and control points accordingly.

Free-Flow Speed Method For tangent links, the free-flow speed must be entered directly. For curved links, the free-flow speed can be entered directly or it can be estimated. In the latter case, the free-flow speed is estimated according to the model discussed in Appendix X.

Grade The percent incline or decline of the segment. This is measured as the elevation change over the length of the segment divided by the segment length, multiplied by 100.

Passing in Oncoming Lane The options for passing in the oncoming lane are:
 * Allowed ‘Direction 1’
 * Allowed ‘Direction 2’
 * Allowed Both Directions
 * Not Allowed

Passing/Climbing Lane Direction The options for passing/climbing lane direction are:
 * None
 * Direction 1
 * Direction 2
 * Both Directions

Passing/Climbing Lane Rule If a passing/climbing lane has been specified, one of the following driving rules can be specified:
 * Slow Vehicles Move Over
 * Fast Vehicles Move Over

2 + 1 Section Not currently functional. The intent for this future feature is to be able to display a 2+1 section as a 3-lane section, with the passing lanes in the middle of the section. A 2+1 section can still be simulated by combining passing lane segments and non-passing lane segments. In this case, however, the passing lanes will be to the right of the regular lanes. You will also need to specify “fast vehicles move over” for the passing lane rule.

Control Point X/Control Point Y These points are specific to horizontal curves. Horizontal curves in the animation are represented as 3-point (quadratic) Bezier curves. The control point is the middle point. These values are set to provide as close a match as possible to the animation representation and the physical representation per the circular curve inputs of radius and central angle.

Detectors Detectors allow one to set points along the segment to measure specific items, such as speed, volume, etc. To set detectors on a segment click on ‘Set’ under ‘Set Detector(s)’ to open the Detectors dialogue box (see Figure below). A detector’s location along the segment is specified by a percentage of the length of the segment. For example, with a 5280-ft segment, a detector set at 25% would be located at 1320 ft in the travel direction. Click ‘OK’ when done.

Entering Traffic Data Press the ‘Traffic Data’ button in the toolbar near the top of the screen to access the ‘Entry Link Inputs’ form (see Figures below). In this screen, the overall entry flow rate per direction and the percentage split for each vehicle type can be specified. After setting values for ‘Direction 1’, press the ‘Save Changes’ button before selecting ‘Direction 2’. After setting values for ‘Direction 2’, press the ‘Save Changes’ button again before closing the form.

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).

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).