This selection also provides several options that bring up the Geometry dialog box with its various data entry screens. Select a screen by clicking its tab at the top of the box. The various data entry screens of the Geometry dialog box are described below, with particular emphasis on signalized intersections.
Input the number of lanes and movements that may occur from each. Note that for a single lane from which all movements can be made, the through lane should be selected.
The following traffic controls may be selected:
Protected
Prot+Permit – left turn is protected first followed by permitted phase
Permit+Prot – left turn is permitted first followed by protected phase
Yield Sign
Uncontrolled
For an explanation of the types of intersection control, please see Chapter 20, Section 20.2.
With a shared lane, the LOS for HCM Ops protected plus permitted phasing is calculated directly, but for an exclusive lane, the calculation is iterative. For this case (Case 3, Left Turns in HCM Ops) the user must remember to insert the permitted left turns for both base and future conditions in the appropriate volume reduction screens. It is suggested that the user first make a run with all left turns being made in the protected phase and, if this cannot occur, then assign “sneakers” at the end of the permitted phase (2 x the number of cycles per hour) as permitted turns. This procedure is similar to what is described in Example 3 in Chapter 9 of the HCM.
Figure 43 Geometry Signal Timing Dialog Box
Data required for signalized intersection analysis are entered on this screen. It is important to set minimum green times to reflect real life conditions (e.g., driver startup and pedestrian crossing requirements). The minimum green times constrain TRAFFIX in its selection of optimal green times and g/c ratios for the intersection. The Minimum times apply by movement. Normally only the minimum green time for through movements need to be entered. Treatments of right turning movements are input along with minimum and maximum cycle lengths, loss time per cycle, yellow + all red per phase, and selection of analysis methodology. If min green is entered for a non-existent movement (no volumes), the entry is ignored and the timing calculations are performed without consideration of this movement.
Available right turn treatments include:
Include: 100% of right turn volumes move only on approach green.
Ignore: Right turn volumes set to zero for analysis
Overlap: Right turn auxiliary arrow turns green at same time cross street left turn gets green arrow. If cross street has only permitted lefts then right turn overlap is same as “include”.
Right turn on red volumes are coded in the Base Volume Reduction and Future Reduction screens in the edit volumes window.
Minimum and Maximum Cycle lengths (in seconds) are coded if it is desired for TRAFFIX to find the optimal cycle length.
The actual cycle (in seconds) to be used in the analysis is coded in this field. If an optimization is performed, this field will be overwritten.
Total loss time per cycle in seconds. This is normally three to four seconds per phase, times the number of phases.
This yellow + all red time per phase (in seconds) is required for HCM operations analysis. It is normally four seconds.
The user may input saturation adjustment factors to be applied to specific movements for the individual intersection. These factors are applied to the default saturation flow rates for the methodology chosen, in addition to any other flow rate adjustments that are appropriate for the particular intersection characteristics (parking, multiple lanes, grades, heavy vehicles, etc.).
On this dialog screen, users may also enter movement-specific saturation flow rates at the individual intersection level without using adjustment factors. These flow rates over-ride the saturation flow rate calculations of the methodology chosen and are used as the Final Saturation Flow Rates for the respective movement. If the value zero is entered for a movement, TRAFFIX will calculate the saturation for that movement normally.
A single screen contains all of the data required for TRAFFIX to calculate the volume adjustment factors used in the HCM Ops Method (with the exception of 1985 HCM Ops which requires that the permitted traffic be specified on the Volume…Base/Future Volume Deduction dialog screens). See Figure 44. Calculations are done by lane group, although the results are shown by movement. Data are entered for the entire intersection (top of screen), individual movements (lane width), or approaches (all other fields).
Indicates the area type where the intersection is located. Toggle choices are “CBD” or “Other”. Default is “Other”.
Indicates the type of signal control. Toggle choices are Fixed Time, Actuated, and Semi-Actuated. Default is Actuated.
Indicates whether or not the intersection is part of a coordinated system. Default is “No”.
Indicates the width of individual lanes by movement. For shared lanes, the program uses the lane width for the through movement. The range for this field is 8 to 15 feet; default is 12 feet.
Percent of heavy vehicles in the traffic flow on each approach. The range for this field is 0 -30 percent. Default, as specified in the HCM, is 0 percent.
Figure 44 Signalized Intersection #4 “Hwy 1 & Carmel Valley Rd.” (Geometry)
The percent of grade for each approach. Plus grades are ascending and minus grades are descending. Values available are from 6% to –6% in two percent increments.
Parking movements per hour on each approach. Range is 0-40 movements; defaults are no parking (NO) and 20 movements per hour where parking exists. This is a combination toggle/data entry field. To make an entry, first toggle the entry from NO to data and then make a numerical entry. The numerical entry is retained for future use when the entry is toggled from data to no parking.
Number of bus stops per hour on each approach. Data entry is similar to the parking field. Range is 0 -40 movements; default is no bus stop stops (NO) and 0 stops per hour when field is turned on. This is a combination toggle/data entry field. To make an entry, first toggle the entry from NO to data and then make a numerical entry. The numerical entry is retained for future use when the entry is toggled from data to no bus stops.
Number of conflicting pedestrians per hour for right turns from each approach. This field is used in the calculation of the right turn adjustment factor. Default is zero, which means in effect that all right turns are protected.
When using the 1985 HCM method, toggle to select between including and excluding any volume in an exclusive right-turn lane when calculating the left-turn adjustment factor for permitted phasing. Specifically, when calculating the V M factor on page 9-16 in HCM 1985, if this setting is “Exclude” then the right-turn volumes in an exclusive right-turn lane are not used.
Percent of right turns that move without pedestrian conflicts. Default is 0 percent.
Specify the main and side street.
The quality of procession in approximate manner. (Five arrival types in 1985 HCM, six in 1994, 1997 and 2000 HCM)
Toggle to select between On and Off. If “Off” is selected, the HCM adjustment factors will not be used for calculating saturation flow.
Use the MLF (multi-lane factor) to calculate saturation flow rates in the 1997 and 2000 HCM Methodologies (has no effect for other methods). If the intersection’s critical V/C is high, the use of MLF should be turned off to more accurately represent likely peak hour operations. Note: For the 1997 and 2000 HCM methodologies, the MLF is applied during the saturation flow calculation, and it is turned on/off in this dialog screen, and the MLF selection in the Volume…Volume Adjustment dialog screen has no effect.
This optional, user-specified factor is applied to the calculated delay (i.e., calculated delay is multiplied by this factor). This screen also includes input fields for the analysis time period and unit extension, which are new parameters used by the 1997 and 2000 HCM methods.
This is another optional user-specified input of Green time or G/C ratio for base conditions. The user should enter values for all movements or check the box to allow TRAFFIX to calculate the values for the unentered movements. This screen is useful for reflecting actual signal timing for the intersection.
The user should enter the actual green time or g/c for each movement.
Special instructions for coding left turn green or g/c times:
If the left turn is protected, code the actual green time that it is protected
If the left turn is permitted, code the actual green time that it is permitted
If the left turn is protected and permitted or permitted and protected, code only the “protected” portion of the green time.
On the Geometry…Green Per Cycle dialog boxes, the user may enter only some G/C ratios or Green times, and TRAFFIX will calculate green times for all other movements. Thus, if the G/C ratio and Green time is zero for a movement, TRAFFIX will calculate the G/C for that movement. This option can also be selected using the check box near the bottom of the LOS Mitigate Screen.
This is another optional user-specified input of Green time or G/C ratio for future conditions. Again, the user should enter values for all movements or check the box to allow TRAFFIX to calculate the values for the unentered movements.
Special instructions for coding left turn green or g/c times:
If the left turn is protected, code the actual green time that it is protected
If the left turn is permitted, code the actual green time that it is permitted
If the left turn is protected and permitted or permitted and protected code only the “protected” portion of the green time.
On the Geometry…Green Per Cycle dialog boxes, the user may enter only some G/C ratios or Green times, and TRAFFIX will calculate green times for all other movements. Thus, if the G/C ratio and Green time is zero for a movement, TRAFFIX will calculate the G/C for that movement. This option can also be selected using the check box near the bottom of the LOS Mitigate Screen.
This option allows the user to enter a description of mitigation improvements and the cost of those improvements. This data is used in the impact fee calculation reports.
This is a very powerful tool for developing improvement strategies to mitigate traffic impacts of the proposed developments. This screen is described in detail in the next chapter.
This selection allows the user to change the index number of the node. This can also be done using the Ctrl-RightClick keystroke combination.
This selection deletes the intersection from the network, along with any links attached to it.
This toggles the selection of the intersection for analysis and inclusion in the results of the evaluation/forecast run.
In the Edit Routes mode this allows the user to select the kind of route marker to be associated with the intersection. If a route marker is already associated with it, there will be a check mark next to that marker type. The marker types are: Start Node, End Node, Segment Separator, Section Separator. This option is available at all intersection nodes. At cross-street nodes, use Ctrl-Shift-RightClick to step through the four marker types; each click moves to the next marker type. You can confirm that you are specifying the correct item by watching the item selection line below the lower left corner of the network window. The intersection icon will also change color with each click. No color means the intersection has not been identified with any of the four items.