Performing environmental impact assessments

To perform environmental impact assessments, you may need vehicle emission data. Using Vissim, you have the following options to calculate the exhaust emission of vehicles.

Note: For emission calculations you need add-on modules (Overview of add-on modules). You must have a license for an add-on module.

Calculate accurate emissions with Bosch Cloud Service

The add-on module Bosch allows you to have emissions of the vehicles in the Vissim network calculated by the service ESTM of the Bosch Cloud after the end of a complete simulation run. You can record the results in evaluations and visualize them on links.

The Quick start guide summarizes the most important steps you need to take to calculate emissions in Vissim (Quick start guide Calculating emissions based on emission classes).

The add-on module Emissions without the add-on module Bosch allows to open Vissim networks containing results of Bosch emission calculations and to display these results. In addition, the defined emission class distributions and the predefined emission classes can be displayed.

Emission classes categorize vehicles

Bosch provides emission data for various vehicle categories in a JSON file for Vissim. The JSON file is saved to the installation directory as part of the installation of Vissim. Vissim accesses this file. In the file, the emission data are broken down by emission class. These differ by the values of their elements Emission vehicle category, Emission vehicle class, Emission stage, Fuel type, Size class, Use class. Based on these six elements, many different emission classes result, which make it possible to distinguish vehicles in terms of their emissions.

The following applies for the following emission classes:

  • Commercial vehicles (HDV, LCV) with emission classes of emission stages EUIV or newer have a diesel particulate filter (DPF).
  • Passenger car diesel vehicles of the EU5 emission standard have a DPF.
  • For passenger cars (PC) with EU4, a distinction is made between vehicles with DPF (fuel type D_DPF) and vehicles without DPF (fuel type D). The emission class for passenger car diesel vehicles with EU4 and fuel type D_MW calculates emissions according to the weighted average based on vehicle registrations.
Setting share of emission classes for vehicle type

Since vehicles with different emission classes can belong to the same vehicle type in Vissim, you specify the relative share of each emission class within an emission class distribution (Defining emission class distributions). This allows you to define a suitable emission class distribution for each vehicle type for which emissions are to be calculated. You then assign the emission class distribution to the vehicle type (Configuring emission calculation for a vehicle type). When you start the simulation run and a vehicle of a vehicle type assigned an emission class distribution is inserted into the Vissim network, it will be assigned an emission class from the distribution.

Using predefined emission class distributions based on HBEFA

The Vissim network file HBEFA_EmissionClassDistributions.inpx with predefined emission class distributions for typical fleet compositions based on HBEFA can be found by default in your Vissim installation under Examples Training\Vehicle Fleet & Settings Defaults. The file contains 168 distributions: 28 for six European countries. The distributions are divided into Urban, Rural, Motorway and Average. From this network file you can additionally read the emission class distributions into your Vissim network (Reading a network additionally). The import of all distributions may take a long time. You then assign the appropriate emission class distribution to each vehicle type for which emissions are to be calculated in Vissim (Configuring emission calculation for a vehicle type).

If Vissim cannot clearly assign a vehicle type defined in HBEFA to a Bosch emission class in the emission class distribution, Vissim distributes the share of this vehicle type to the other emission classes in the distribution.

Calculating and evaluating emissions

Activate the Bosch emission calculation in the Evaluation Configuration window before starting the simulation run (Performing evaluations).

For each vehicle of the vehicle types for which emissions are to be calculated, Vissim generates a trajectory during the simulation run. Vissim sends these to ESTM after the end of the complete simulation run to calculate emissions.

The trajectory contains data for identification as well as the emission class of the vehicle, furthermore waypoints recorded per second with the speed (km/h) of the vehicle and the inclination (%). Reversing vehicles are not recorded.

Vehicles that do not produce emissions can be considered in the Emission free emission class. No trajectory is generated for these vehicles and thus no data is sent to ESTM.

You can deactivate or activate the Bosch emission calculation for each link and connector in the Vissim network (Attributes of links), (Attributes of connectors). The deactivation may reduce calculation speed. However, Vissim does not generate a trajectory for the vehicle on deactivated links or connectors. If the vehicle then again reaches a link or connector for which Bosch emission calculation is activated, Vissim generates a new trajectory from the start of this link or connector. When starting a trajectory, Bosch uses emission calculation data based on the operating temperature of the exhaust tract. This way, emission calculation results are not influenced by different operating temperatures of the exhaust tract when a vehicle travels through several Vissim network sections containing activated and deactivated links or connectors.

The calculation time depends on the amount of data and may take several minutes. The calculated emissions are transferred back to Vissim. An Internet connection is required to send and receive the data. The Windows proxy server settings are used for this purpose.

If due to a timeout data transfer is stopped before completed, Vissim shows the trajectory parts for which there is no emission data. The data transferred is available for evaluations in Vissim.

Calculation results are transferred for fuel consumption and for the following emissions: carbon monoxide, carbon dioxide, nitrogen oxides, burnt hydrocarbons, particulate matter. You can record these in the following evaluations:

In the network editor, you can visualize the results on links (Graphic parameters for display of link bars and lanes), (Assigning a color to links based on aggregated parameters). You can also display results in charts (Creating charts).

If emissions are not calculated and are not transferred back to Vissim, their value = 0.

Messages in Vissim for Bosch emission calculation can contain comma separated values of the attributes of the emission classes. These are displayed in the following order: Vehicle category, Emission vehicle class, Emission stage, Fuel type, Size class, Use class. If no value is set for an attribute, the message displays ", - ," at this point.

The emission calculation takes into account that, depending on the fuel type of the engine, the exhaust tract of a vehicle will not reach operating temperature until some time after the vehicle has entered the Vissim network. This also applies to vehicles that pull forward out of the parking lot after parking. The time period can be up to approximately two minutes. In addition, the emission calculation takes into account that the exhaust tract of public transport vehicles is warm when they are waiting at stops. If you want to ensure that the exhaust tract is already at operating temperature when the vehicle enters the area of the Vissim network where you want to have emissions calculated for these vehicles, extend the link on which the vehicle will be inserted upstream and position the vehicle input accordingly. This applies in the dynamic assignment accordingly for the origin parking lot.

Limitations of the emission calculation

Emissions are not calculated under the following conditions:

  • the vehicle is parked in the parking space of a parking lot
  • the vehicle is a platoon trailing vehicle
  • the vehicle reverses or backs out of a parking space
  • in mesoscopic simulation

Simplified emissions determination via node evaluation

Node evaluation also determines exhaust emissions (Evaluating nodes). The basis for these are formed by standard formulas for consumption values of vehicles from TRANSYT 7-F, a program for optimizing signal times, as well as data on emissions of the Oak Ridge National Laboratory of the U.S. Department of energy. The data refers to a typical North American vehicle fleet and does not differentiate between individual vehicle types. This allows you to use node evaluation for a more simple comparison of the emissions produced during different scenarios.

Precise method with EnViVer Pro or EnViVer Enterprise

EnViVer Pro is a program used to calculate exhaust emissions based on detailed vehicle record data from Vissim. Using this add-on module, you can determine the exhaust emissions for individual vehicle types.

The statistical emissions model in EnViVer Pro and EnViVer Enterprise calculates realistic values for CO2, NOx and PM10 emissions of different vehicle categories. The calculated emissions are based on speed-time profiles of vehicles. The emission models are updated annually and are kept for future calculations. With the update, new emission models are added and existing models, if available, are updated. EnViVer Pro and EnViVer Enterprise thus provide both current and previous emission models, which allow you to easily compare or recalculate values (Overview of add-on modules). For questions regarding the purchase of EnViVer Pro and EnViVer Enterprise for Vissim, please contact PTV GROUP under the following e-mail address: traffic.info@ptvgroup.com. For information on the products, please refer to the website of the provider TNO  (www.tno.nl).

The COM interface or API approach with EmissionModel.dll

This approach requires programming knowledge, as you must create the EmissionModel.dll file or write your own scripts for using the COM interface. It allows you to use your own calculation algorithms and simulation data as input.

EmissionModel.dll file

For the calculation of emissions, you can access the file EmissionModel.dll (Accessing EmissionModel.dll for the calculation of emissions). You must provide the EmissionModel.dll. It is not part of Vissim. The following data is transferred via the interface for all vehicles and each simulation time step:

  • Accelerations
  • Speeds
  • Weights
  • ID numbers
  • Vehicle types
  • Gradients
COM interface

To calculate emissions, you can create your own scripts and/or integrate your own applications into Vissim. Using the COM interface, for each time step, you can access all Vissim attributes, e.g. position, speed and acceleration of the vehicles (Using the COM Interface).

Noise calculation

Noise calculations are carried out using specialized external software, e.g. CADNA or SoundPLAN. Vissim can provide specific input data for these programs. Alternatively, you can use the COM port, write your own script or embed your own application into Vissim for noise emission calculation (Using the COM Interface).

Calculation of ambient pollution

Concentration values determine the impact of environmental interference factors affecting human health and the natural environment. Concentration values are not calculated in Vissim, but in external software programs that specialize in concentration value calculation. Vissim can provide specific input data for these programs.

Superordinate topic:

Performing evaluations