Volumes

One of PTV Vistro’s most powerful features is its trip accounting capability. With PTV Vistro there are multiple layers of volumes and adjustments that can be entered to result in the desired analysis volume. When performing a traffic impact analysis (TIA) in PTV Vistro, trips associated with a development are automatically calculated for each turn movement in the network once the trip generation, distribution, and assignment have been performed. Additionally, PTV Vistro provides place holders to make volume adjustments, such as in-process trips from an already approved, but not yet built development that needs to be included in the analysis.

In the case of a non-TIA project, all of the TIA-related parameters are grouped together and can be collapsed in the volume setup table by using the arrow button to the left of the TIA Demand header. Parameters that appear italicized in the volume setup table are calculated values. The Volumes workflow task table is shown below in the figure of the Volumes Table.

All parameters in the volume setup table are described in the table Volumes Parameters below the figure.

Figure 9: Volumes Table

Table 5: Volumes Parameters

Parameter

Description

Units

Basic Volume Inputs

Number

Unique number of the intersection. Intersections are numbered consecutively. However the preset number may be overwritten by another number that does not already exist in the network.

Intersection

Name of Intersection

Approach

Direction of approach as defined under the intersection setup table.

Lane Configuration

Shows lane configuration as defined in intersection setup table.

Turning Movement

Identifies the movement (Left, Thru, Right, U-Turn)

Base Volume Input

Summary of Base Volume Input, description below.

veh/h

Total Analysis Volume

Summary of Total Analysis Volume, description below

veh/h

Base Volume Input

Base traffic volume input by user.

veh/h

Base Volume Adjustment factor

User definable adjustment factor to apply if desired to base volume input. An example application would be a seasonal adjustment factor.

Default = 1.0000. Range = 0 - 99.9000

Final Base Volume

Base volume representing the base condition.

= Base Volume Input * Base Volume Adjustment Factor

veh/h

Heavy Vehicles Percentage

Percent of heavy vehicles for each turn movement.

Default = 2. Range = 0 – 100

Proportion of CAVs [%]

Proportion of CAVs (connected and automated vehicles) in traffic stream, Range is [0.00;100.00], (HCM 7th edition)

Proportion of EVs [%]

Proportion of EVs (electric vehicles) in traffic stream, Range is [0.00;100.00], (HCM 7th edition)

Growth Rate

Growth rate to be applied as multiplicative factor to adjust volume to future year analysis.

Default = 1.000;

TIA Demand

In-Process Volume

User definable volume input typically used to account for trips already approved by a nearby development that is not yet in place.

veh/h

Future Background Volume

Future volumes before any trips are added for the new development.

= Final Base Volume * Growth Rate + In-Process Volume

veh/h

Site-Generated Trips

Trips calculated from the new development(s) based on the trip generation, distribution, and assignment paths. Making changes to any component of the trip generation process will result in a change to this value.

veh/h

Diverted Trips

Trips attracted from the traffic on roadways within the vicinity of the development site but require a diversion from that roadway to another roadway to gain access to the site. Diverted trips add traffic to the roadways adjacent to a site. Value may be negative or positive.

veh/h

Pass-by Trips

Trips made as intermediate stops to the development on the way from an origin to a primary trip destination. This field is used in tandem with the Trip Generation for a zone. Primary trips (non-pass-by) can be generated and assigned to the study network, while pass-by adjustments at project driveways can be entered in these fields. Value may be negative or positive.

veh/h

Existing Site Adjustment Volume

User defined volume adjustment to account for trips either added or removed due to changes in the land use to accommodate the new development. For example, an existing apartment complex is removed to allow construction of a new retail shop. In this case, trips from the apartment complex have been accounted for in the base volume and now need to be removed. This parameter may be positive or negative.

veh/h

Net New Trips

Total new trips added to the system after accounting for all adjustments.

= Site Generated + Diverted + Pass-by + Existing Site Adjustment Volume

veh/h

Additional Volume Adjustments and Calculations

Other Volume

User definable volume not accounted for by other volume parameters

veh/h

Future Total Volume

Total future volume after all site generated trips and volume adjustments have been made.

= Future Background Volume + Net New Trips + other volume

veh/h

Right-Turn on Red Volume

Volume adjustment to account for vehicles per hour that turn right on a red signal. Value is positive.

If the Right Turn on Red Method is set to Absolute, a right-turn on red volume value can be entered

If the Right Turn on Red Method is set to Percentage, a right-turn on red percentage value can entered. This value will calculate right turn on red volume based on a percentage of the movement's Future Total Volume. Global Settings or Multi Change can be used to set a default Right Turn on Red Percentage.

veh/h

Total Hourly Volume

Total hourly future volume after accounting for right-turn on red

veh/h

Peak Hour Factor

PHF based on the Highway Capacity Manual used to adjust the hourly volume to reflect the 15-minute peak flow rate.

Default = 1.0000. Range = = 0.25 – 1.0000

Other Adjustment Factor

User defined adjustment factor to account for factors not accounted for by any other parameter.

Default = 1.0000. Range = 1 – 99.9000

Total 15-Minute Volume

Estimated total vehicles during the highest 15-minute period of the peak hour.

= (Total Hourly Volume * 0.25 / PHF) * Other Adjustment Factor

vehicles

Total Analysis Volume

Calculated total analysis volume, including all volume adjustments and factors defined.

= Total 15-Minute Volume * 4

veh/h

Presence of On-Street Parking

Checkbox to indicate on-street parking is present and a factor in the analysis

On-Street Parking Maneuver Rate

Number of on-street parking maneuvers per hour that occur on the approach adjacent to the movement indicated

#/h

Local Bus Stopping Rate

Number of bus stop maneuvers per hour that occur on the approach

#/h

Pedestrian Volume

Pedestrian volume on crosswalk of selected approach. This volume is utilized in the HCM (2010 and 2000) calculation and to generate pedestrian input for crosswalks when exporting to Vissim.