Step 3 Draw Streets, Zones, and Gates

The critical intersections, developments, and gateways are connected by a network of street links. Street links can be north, south, east, west, or diagonal. The top of the monitor is north. Diagonal links are assigned a direction corresponding to the side of the node (intersection, zone, or gate) to which they are connected. TRAFFIX uses the network data to display the network on the screen, to draw paths on the screen, and to verify the accuracy of the paths.

An intersection can have no more than four approaches, and no more than two of these approaches can be east-west or north-south. Although this may at first glance appear to be a constraint, most street networks in the United States can be easily represented by simply rotating the compass direction.

Step 3.1 Draw the Network

Drawing and editing a network is a very simple task. Click the network button to enter the Edit Network mode. (This is the default mode when the program starts.) A toolbar appears on the left of the network window, including the ten network drawing/editing tools shown in Figure 46. Some of these tools have options associated with them. To view or change these options simply place the cursor over the tool icon and Right Click. This will bring up a dialog box with the available options. For example, the three intersection tools (signalized four-way stop, and unsignalized) have the options to display the intersection index only, the index and the base LOS, or the index and the future LOS. They also have the option to select/unselect all intersections for analysis. All node tools also have the option to draw one-way or two-way links automatically as nodes are placed. The zone tool has options to select/unselect all zones for inclusion in the analysis.

To draw a network, simply click on the tool you wish to use, then click in the network window where you want to position the item selected. Also see TIPS FOR DRAWING NETWORKS on page 174. Intersections, zones, and gates are positioned by clicking once.

Links can be drawn automatically as the nodes are placed, by selecting this option for the node tools. Either one-way links or two-way links can be drawn (holding the Ctrl key while placing nodes will temporarily toggle from one-way to two-way, and vice versa). Nodes are selected (highlighted) as they are placed. Links are drawn from the last selected node to the newly placed node, or to an existing node if you click on one. To draw a link between two nodes already placed (but not the last one placed) first unselect all nodes (Ctrl-A), click on one of the existing nodes, and then click on the other existing node.

Links can also be drawn with the Link tool by clicking a node, moving the cursor to another node, and double clicking to turn the link tool off or single clicking to continue drawing links. Press Esc to cancel the link currently being drawn.

Text is positioned by clicking once to place an empty text field, then with the cursor over the field, Right Click to bring up the text dialog box for entering text and selecting fonts, font color, and font size. Text fields are useful for annotating the network for easy user orientation in screen displays or network printouts. The user can place street names, notes, or any text information desired in these fields. These fields are not tied to links or nodes and must be moved individually, if the user reshapes the network by repositioning nodes or links. There is an Undo feature that works during network drawing. This is on the Edit menu and can also be activated by the Ctrl-z keystroke or the Backspace key.

Approximate positioning is adequate for TRAFFIX analysis purposes. If precise positioning is desired, this is aided by the position coordinates, shown below in the lower right corner of the network window. These are the coordinates of the cursor position. The options provided under the A rrange pull-down menu are also useful for this purpose. There is also a Snap to Grid option which can be turned on or off from the F ile…Preferences menu selection. This causes nodes to be placed in a grid pattern with spacing in increments as specified by the user. This is especially useful for drawing orthogonal street networks. After the initial network is drawn, turn this feature off. If it is on, you will not be able to move network items to positions that are not on the grid pattern. Also, if it is on, you will have difficulty placing new nodes on existing links (between two existing nodes); you may not be able to place nodes exactly on the desired link and TRAFFIX will therefore not make the link connections you intend.

To delete an item, point to it and use Ctrl-Shift-Left Click . To confirm that you are selecting the item you want, watch the Item Selection Line below the lower left corner of the network window. You can also use the Right Click pop-up menu to delete nodes. Note that all attached links are deleted when a node is deleted.

The intersections, zones, and gates will be numbered automatically in the order that you insert them. These index numbers can be changed later if desired using the “Change Index Number” keystroke, Ctrl-Right Click , or from the node pop-up menu accessed with Right Click while pointing at the node.

Links can be drawn at any angle desired; however, no intersection (zone or gate) can have more than four legs (eight one-way links). When drawing links on an angle, pay careful attention to which side of the intersection (zone or gate) box the link is being attached (this can be seen more easily if you zoom in on the intersection, so that each individual one-way link is visible). Only one link in each direction is allowed to be attached to each side of these boxes.

Intersections, zones, gates, and text can be moved using Left Click-Drag . The attached links automatically move along with nodes.

To reorient or rotate text, choose the text tool, point to the last character in the text string until the curved-arrow rotation icon appears, then Left Click and drag the text base line to the orientation desired and release. The text will then appear in the new orientation. For greater precision, stretch the base line to a longer length before releasing the Left Click . To invert the text string (rotate 180 degrees), point to the first character in the text string until the curved-arrow rotation icon appears, then Left Click.

Links can be repositioned using Left Click-Drag with the cursor near the end of the link to be moved. Zoom in so that individual one-way links are visible. Select the Link tool and position the cursor on the link near its end. Look for the small square handle to appear then Left Click-Drag the end of the link to its new position (another node or another side of the current node).

At small scales (zoomed out), you can confirm that you are selecting the item you want by watching the item selection line below the lower left corner of the network window. The item selection line shows the item’s index number, connection points, name, and selection status.

To change an intersection’s type, first select the tool that corresponds to the new type (signalized, cross street, unsignalized, four-way stop, roundabout) and then click on the intersection to be changed. Note: this changes the intersection type for all scenarios.

The Cut, Copy, and Paste options under the E dit menu can be used to modify networks. The Cut option deletes selected (highlighted) items from the network, and also places a copy on the clipboard. The Copy option copies selected items to the clipboard. The Paste option inserts from the clipboard items previously placed there with the Cut or Copy options. The Duplicate option does the Copy and Paste options in one step. The Paste option can be used to move items from one network to a new network, and it can be used to copy items in one network to the same network. In the latter case, the new item is placed near the existing item and must be moved to its new location. The Delete key will also remove items from the network, but they are not placed on the clipboard and cannot be retrieved with the Paste command.

Note : The Cut, Copy and Delete keystrokes act on all items in the network that have been selected for editing (highlighted). It is easy to inadvertently select extraneous items in portions of the network that are not presently displayed on the screen. Therefore, it is good practice to unselect all items ( Ctrl-A ) before starting a Cut, Copy, or Delete operation. There are also Select All and Unselect All options on the Edit pull-down menu, which are useful when doing successive cut or copy operations.

These commands can be used to copy data from one node to another within the active database. The data at one node (for all scenarios simultaneously) can be copied to one or more existing node(s) as follows: select the first node, copy it with Ctrl-C , unselect all items ( Ctrl-A ), select the second node(s), and paste the data with Ctrl-V . For copying data from one database to another database, the Copy Database Data features on the Tools pull-down menu must be used.

The entire network can be printed using the File…Print menu option.

It is generally easier to code extra links (for future facilities) into the base network, than it is to add new links to an existing network data set.

It is highly recommended that zones and gates be connected to a network with at least two links. In this way, an additional zone or gate can be added later that has the same access to the network. The link connected to a zone or gate cannot be easily split with an intermediate node.

After links are created, nodes can be added between the two end points and the original link will automatically be divided. This feature is a convenience for making unanticipated changes to networks but should only be used when necessary. The insertion of nodes will not affect existing paths or routes in memory; however, an exception to the ability to split links involves links connected to either a gate or zone. TRAFFIX is unable to adjust the paths and routes if a node is inserted at such points, and the affected paths and routes will have to be redrawn. TRAFFIX is also unable to adjust the network if a node is deleted. New links will have to be created, and all paths using the links that were deleted will have to be redrawn.

Step 3.2 Arranging Network Items

The A rrange menu contains the following options for changing the layout and indexing of network items already drawn (Tip: It is a good habit to automatically “unselect all items”, Ctrl-A, before selecting the items to be arranged):

Align -Left - align selected objects on their left edge

Width Center - align selected objects on their width

Right - align selected objects on their right edge

Top - align selected objects on their top edge

Height Center - align selected objects on their height

Bottom - align selected objects on their bottom edge

(Align operations are performed relative to the last item selected.)

Spacing Height - equally space selected objects vertically

Width - equally space selected objects horizontally

Grid - permanently changes the network’s grid spacing

Sort - Renumber selected object indexes beginning with a starting index number supplied by the user.

Renumbering proceeds in order from left to right and then from top to bottom based on the position of the selected items. The first selected item (top leftmost) is given the starting index number, and each successive item is given the next index number in order.

Selection of items is done using the selection and unselection key strokes described in Chapter 2 under HOT KEYS AND OTHER HELPFUL TIDBITS. Note that this selection does not select items for inclusion in the forecast analysis. The colors used to highlight items selected for cutting or copying are different than the colors used for selection of intersections and zones to be used in the forecast analysis.

Step 3.3 Enter Intersection Data

For those intersections where level of service analysis or turning movement forecasts are desired, additional data must be coded. Volume, geometry, and traffic control data must be provided for these special analysis intersections.

Basic data for intersections, including base volumes, can be entered into the LOS Mitigate screen. There are also buttons on this screen to call up the Volume dialog screen and the Geometry dialog screen.

First move the cursor to the desired node.

RightClick to bring up the intersection dialog box.

LeftClick the Name option

Type in name (typically street names) that will be used on the reports (e.g. First & Main St). The name field is 48 characters in length. A name as short as possible (with St, Av, & Bl abbreviations) will guarantee that the name will appear in full on every report.

TRAFFIX does not have separate fields for north/south and east/west streets. It is recommended that the standard convention for entering street names be used, e.g. enter all north-south streets first, or use the “comment” field to enter notations about directional orientation (e.g., N/S: Main St E/W: First St).

The primary identification of locations in the program is the intersection name. This is the name that will appear on all reports. Street names and other annotations to the network can be added using the Text Tool, by placing text fields for street names at strategic places along the network and by adding other labels and notes. Annotations added using text fields will be displayed on the screen and on network printouts.

Access the Base Volume Screen (Right Click…Volume) and enter base hourly volumes for the intersection. If you want TRAFFIX to apply special adjustments to individual movements (in addition to the normal multi-lane and passenger car equivalent factors), enter these factors for each movement in the appropriate dialog boxes. These adjustments include growth factors, peak hour factors, volume adjustment factors, and volume reductions for base and future volumes. A description of these adjustments is provided in Chapter 13.

Figure 15 Volume Input Screen

Intersection-wide as well as individual turning movement adjustment factors can be applied for peak hour factors, volume adjustment factors, and growth factors.

Also, a universal volume adjustment factor and/or growth factor can be applied to all intersections. The fields for these factors can be accessed in the O ptions …Global …Parameters & Title menu.

The growth factor is applied to base volumes only and is used to simulate growth in background traffic from the present to a future year. The growth factor is not applied to volumes generated by zones. On the other hand, the Volume Adjustment Factors and the Peak Hour Factor are applied to both the base and future volumes. Output reports for turning movements and link volumes reflect the growth factors; all other input adjustment factors or internally computed factors are excluded from these two reports.

TRAFFIX determines the level of service for both signalized and unsignalized intersections. TRAFFIX allows different intersection controls at different intersections to be analyzed at one time. It is even possible to use different methods of signalized intersection analysis at different intersections. Data entry procedures are described below, and additional information is provided in Chapter 13.

First collect signal operation (phase sequence, right turn on red, cycle length, G/C ratios or green times, minimum green times), and geometry (lanes) information. Make field observations if possible to identify unusual intersection operational features (such as heavy pedestrian flows, uneven lane stacking, right-turns on red, permissive left-turns, etc.) that might affect intersection capacity. Review Chapter 20 for advice on how to achieve the best TRAFFIX results when coding this information.

With the cursor over the desired intersection, Right Click to bring up the intersection dialog box, and select the Geometry option to bring up the geometry dialog box.

The Controls screen provides for traffic control designations on the north/south and east/west approaches. These fields establish the appropriate methodologies that can be used to calculate the level of service. The user can select the desired approach control from the drop-down box on each approach.

For signalized intersections, five options are available: Protected left turn phasing, Permitted left turn phasing, split phasing (each approach moves separately), Protected + Permitted, and Permitted + Protected. The first three options are self-explanatory. With Protected + Permitted phasing, first left turns are protected and then permitted left turns can occur during the green time for through movements. The operation of Permitted + Protected phasing is the reverse of the Protected + Permitted phase. As implemented in TRAFFIX, the user must estimate the number of permitted left turns and enter them in the Reduced Volume screens for Base and Future conditions. Thus, green time will be allocated only on the basis of the left turns that occur during the protected phase. Phasing can be specified for each approach and the user is responsible for checking the validity of the phasing combinations used.

For unsignalized intersections, three options are available: stop sign control, yield control, and uncontrolled. When either “stop” or “yield” is specified for one set of approaches, uncontrolled must be specified for the other set of approaches for the Highway Capacity Manual unsignalized method to be applied. If “stop” or “yield” is selected for all approaches, TRAFFIX will apply the three-way and four-way stop sign control methodology described in TRC 373, or the HCM all-way stop methodology, based on the user’s choice.

When the intersection is signalized, the Geometry dialog box has screens for entry of various signalization parameters and adjustments. Alternatively, if the intersection is unsignalized, the Geometry dialog box has appropriate screens for entry of various unsignalized parameters and adjustments.

For Signalized Conditions

Click the Signal Timing tab, then enter for each movement, as appropriate, minimum green times in seconds.

Select right turn (RT) options (Include, Ignore, Overlap); default is Include.

Enter for each intersection, as appropriate, the maximum cycle length, the actual cycle length, signalized analysis method, and total intersection loss time. Maximum cycle length is a global parameter but can be modified either in the Options… Global…Parameters screen or in the signal screen for individual intersections. Actual cycle length can be entered, if known. If it is zero, the optimum cycle length as calculated by TRAFFIX will be inserted after the forecast is run. Thereafter, it can be modified by the user. A default analysis method is provided when the intersection is added to the network, but a different method can be selected in this screen if desired. Total loss time must be entered by the user for each intersection.

All of the data in the Signal Controls, Signal Timing, Base Volume screens can be entered while in the LOS Mitigate screen (accessed from the intersection dialog box - Right Click while the cursor is over the intersection). The other intersection data entry screens can then be accessed after the basic data have been entered (try the “Edit Geometry” button on the LOS Mitigate screen).

For signalized intersections being analyzed with the HCM Operations Methods, data may need to be entered into the HCM Saturation Calc Input screen. The other screens are for entering a Delay Adjustment factor and Green time (or G/C ratio) for base and future conditions. Data entry for these screens is described in detail in Chapter 13.

For Unsignalized Intersections

In the Geometry dialog box, click the PCE tab to enter data to establish passenger-car-equivalent values and the Critical Gap tab to establish critical gap adjustments. Note that the inputs of the unsignalized intersection methods are different for the various HCM methods.

Click the Lanes tab to enter the lane geometry. The box closest to the edge of the screen for each approach is for coding a shared left-thru-right lane. No warnings about conflicting lane codes (e.g. Two shared left-thru lanes) are shown on this screen; however, warnings are issued during the Forecast run and when using the LOS Mitigation screen.

Click OK to return to the network editing screen. You must use the normal TRAFFIX save functions, under the Files menu or the button, to save your entered data to disk.

With the cursor over the intersection, RightClick and choose Improvements to enter the description and cost (in millions of $) of any intersection improvement projects which should be included in the impact fee analysis (optional). Click OK to exit to the editing screen. If you want the output to give percents for each zone, enter 1.0 for cost. Note: Typically you will not know what improvements are needed until you use the LOS Mitigate screen.

Step 3.4 Select Intersections to Be Included in Forecast Analysis

The user has the option of quickly selecting/unselecting all intersections or selecting intersections individually. In the toolbar, RightClick on any one of the four intersection tool icons (signalized, 4-way stop, unsignalized, or roundabout) to bring up the options pop-up menu Choose the Select All For Evaluation or Unselect All For Evaluation options. The Select All For Evaluation choice is the easiest way to ensure that all intersections have been included in the analysis. Cross streets are not selected by this option; only signalized, four-way stop, unsignalized, and roundabout intersections are selected. If an intersection is selected, the square around the intersection icon will change color. To select/unselect intersections individually, place the mouse cursor over the desired intersection, then use the Ctrl-Shift-RightClick keystroke to toggle the selection on or off, or use the node pop-up menu (RightClick).

Note that this “Selected for Evaluation” selection is different than the selection of items that is done for the purpose of cutting or copying. Any selections made for cutting and copying do not affect the selections made for inclusion in the forecast analysis. The colors used to highlight selected items are different for each kind of selection.

Step 3.5 Printing the Network

To print a hard copy of the network, choose File…Print. The dialog box allows the user to specify the print scale, select “Scale to Fit Page”, or specify multiple print copies. To print only the portion of the network displayed in the editing window, choose File…Print Window.

TRAFFIX requires that printers or plotter drivers be set to print “EMF” graphic format rather than a “RAW” format. With the RAW format (common to many drafting specific software applications), the print job is completely processed into printer specific language which is then spooled or sent directly to printer. DOS apps only use RAW. In the EMF (enhanced metafile) format, the print job is only partially processed, whereupon GDI.exe does the rest of the processing, releasing control of your app faster than RAW. Windows uses the Windows graphic functions to print.

Step 4. Define Arterial Routes

Step 5. Enter Zone Data