Two-Lane Highway

Main Page > Technical Documentation > Network Setup > 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.

The orientation angle and grade inputs are described here.

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.

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).