Parameters & Title

These options allow the user to specify the key global parameters to be used in the analysis, and enter the titles to appear on the output reports for the current scenario. See the dialog box on the next page. These are two of the most important data entry screens in preparing a TRAFFIX database. The data on these screens are used globally throughout the database.

Up to three lines of titles for each scenario’s reports can be entered on the Title’s screen. The comment lines will not appear in any report but can be used to provide comments on the analysis that will be helpful to the user at a future date. The default heading for the passerby trips row on the LOS Computation output reports is PasserByVol.

Some users prefer to use the passerby volume field for purposes other than accounting for pass-by trips (such as for Approved trips). The user has the option to rename the pass-by heading using the field provided on the Titles dialog box. This will apply at all intersections for the current scenario, unless the user enters a different value for an individual intersection in the Volume…PasserBy Volume dialog screen. All scenarios that share the same Command data set will have the same label for this item.

The following options are on the Parameters Screen:

Volume Adj/Growth Factor/Delay Adj – These are global adjustment factors.

Delay Parameters [t, a, b, n, m] – These are delay parameters used in the delay calculations for non-HCM signalized methods.

Maximum Cycle – This is the maximum cycle time.

Population – This is the default population.

Signalized LOS Method/Unsignalized LOS Method/4-Way Stop LOS Method/Roundabout LOS Method – These are the default LOS methods used when an intersection is created. When you exit the Parameters Screen and you’ve changed these values, you will be asked if you’d like to apply the new default method to all the existing intersections. You have the option to accept or decline. If you accept, all existing intersections will have their method changed to the new default method.

Arterial LOS Method – This is the arterial method used for the arterial calculation.

Calc HCM Sat Adj? – This global flag is used to turn the HCM saturation adjustment calculation on and off.

Use HCM MLF Sat Adj? – This global flag is used to switch between using the HCM MLF saturation adjustment calculation (on) and the Traffix MLF saturation adjustment calculation (off). For pre-1997 HCM methods, the HCM had no MLF saturation adjustment calculation so this flag is ignored for pre-1997 HCM methods and the Traffix MLF saturation adjustment calculation is always used for pre-1997 HCM methods.

Metric Units? – This global flag is used to turn on and off the use of metric units.

Lock Network? – This global flag is used to lock the network i.e. intersection positions cannot be changed. To avoid accidental changes to the network layout after it is created, the user may “lock” the network with this feature. This parameter is in effect for all scenarios, regardless of the scenario in which it is set.

Report Only Selected Intersections? – If this global flag is ‘on’, then only intersections selected for evaluation will be evaluated and reported. If this global flag is ‘off’, then all intersections will be evaluated and reported.

Report G/C or Green Time? – This global flag is used to choose whether G/C ratios or Green times are to be used in the output reports and on the LOS Mitigate screen

Average Vehicle Length – The average vehicle length used in queue calculation.

Report LOS Grade Modifier? – This global flag is used to choose whether or not LOS grade modifiers (+ and -) are to be used with the LOS letters in reports and on screen for signalized intersections (see the tabulation on the next page for definition of the modifier ranges).

Calc Queue Method [HCM2000 Queue Method] – This option is used to select the queue method to use in the evaluation. The user has four options for calculation of queue length.

One option is referred to as the Australian method. It calculates the mean back of queue after start of green, and must be multiplied by a peaking factor to arrive at a design queue length. This method includes a term that calculates the number of vehicles remaining after the end of green, and experience indicates that the resulting queues over-estimate the actual mean queues.

The second method is a Design Queue Length calculation, which computes the mean maximum queue length at start of green, and then computes the mean maximum back of queue some time after the start of green, and then estimates the 95^th percentile design queue by multiplying this mean by a factor of 2.

The third method is known as the back of queue methodology and it provides a greater variance in the expected queue lengths due an analysis that expands beyond the 95^th percentile queue. This model for predicting queue lengths is described in Appendix G of the HCM 2000.

The fourth method is an Average Queue Length calculation, which is the Design Queue Length divided by 2.

All four methods provide a queue length in terms of total vehicles by lane group. If the user wants stacking distance per lane, these queues need to be multiplied by an average vehicle length in feet (or meters) and divided by the number of lanes in the lane group.

Users select the desired method from the Options…Global Data… Parameters dialog box. Note that there is a field provided here for the average vehicle length to be used. This is needed for the Design Queue calculation method, but the queue lengths are still reported in terms of vehicles (not distance).

Real World Coordinate System – This option is used to turn on and off the use of the real world coordinate system and set how the real world coordinate system maps to the Traffix internal coordinate system. When the real world coordinate system is on, the coordinates in the lower right of the screen will be reported in the real world coordinate system. The mapping values are also used by the Link Data Screen to calculate the length of links. The mapping values can be changed without turning on the real world coordinate system.

Figure 35 Titles Dialog Box

Figure 36 Parameters (Global) Dialog Box

Table 8 Signalized LOS Grade Modifier Scale