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Project Level Analyses

Chapter 3. Application of VSP Profiles in MOVES Project Level Analyses Under Various Congestion Conditions

A. Using MOVES for Project Level Analyses

Three modeling "scales" or "levels" are available in MOVES: national, county, and project levels. The national scale is the default selection in MOVES; when selected, data collected on a nation-wide level is apportioned or allocated to states or counties. This data will differ from data collected for a specific state or county. For a finer level of detail about a particular area, the user can choose the county scale. With this scale choice, the user must replace national default allocations with local user-supplied data. The county scale is intended to be used when doing SIP or regional conformity analyses.

The project scale, which is the focus of this study, is the finest level of modeling in MOVES. It allows the user to model the emission effects from a group of specific roadway links and/or a single off-network location. The definition of a roadway link is a section of any road where a vehicle is moving for more than three seconds. An off-network location is an area of activity that is not a roadway, for example a parking lot, where vehicle starts and extended idling emissions are produced. The use of the project scale requires the user to define the project (i.e., specify all individual roadway links and/or the off-network area). All of the required project level data can be input through the MOVES Project Domain Manager. At the project level scale, the VSP profiles developed as discussed above can be used as one of the inputs to the MOVES Project Domain Manager.

The inputs that need to be provided for use in a MOVES project level run are listed below. For detailed information on these inputs, consult EPA's MOVES User's Guide5.

Link-level files:

Other data:

B. Applying the VSP Profiles from the Congested and Incident Microsimulation Traffic Modeling to a MOVES Simulation

1. Congested Scenarios Modeling

For all the congested scenarios, except for the ones dealing with incidents, the selection of the appropriate operating mode distribution profile to best model a user's specific project-level congestion situation is as follows:

This boils down to essentially finding the test links and scenarios that best match with the application being studied and then applying the corresponding operation mode distribution file in a MOVES simulation.

2. Incident Scenarios Modeling

Application of the incident scenarios requires more effort on the part of the analyst. The reason is that the simulations were run for very specific incident conditions, rather than for average recurring congestion conditions, so the results are only applicable to the incident characteristics for a given scenario. If the analyst is interested in the overall effect of incidents on a series of project links, independent estimates of the likelihood of incidents with a given lane blockage and duration must be made, and the results weighted. So, for a given peak period, the analyst must determine the probability of each duration by blockage combination occurring; Table III-1 shows these combinations, where the cell entries are the probability of occurrence. Ideally, the probability data for doing this should be developed from locally archived incident management logs. (Many traffic management centers keep track of incident characteristics.)  Consider a simplified example where all incidents that occur block 50 percent of the available lanes. The probabilities for these lane-blocking incidents are as follows:

MOVES analyses should be run for each of these conditions. The resulting emissions are multiplied by the probabilities, and summed to get total emissions on each link. A more detailed analysis would involve estimating the percent of VMT represented by each cell, but this requires that incident management and continuous traffic data be fused. That is, a modeler would have to determine the VMT exposed to each condition in the cells of the matrix.

Table III-1. Estimating the Probability of Incident Occurrence

Percent of Lanes Blocked by Incident6

Duration

0%

25%

50%

75%

30 minutes

(recurring congestion only)

45 minutes

60 minutes

90 minutes

To apply this method with MOVES, for a given V/C ratio for a freeway bottleneck area, all of the incident duration/blockage operating mode distributions are input to MOVES as well as the recurring only condition (i.e., either the on-ramp or freeway-to-freeway interchange conditions). The resulting emission estimates from MOVES are then prorated by the probabilities in Table III-1.

C. Developing the Remaining MOVES Link-Level Files

After selecting the appropriate operating mode distribution file to apply in the user's situation, as discussed above, the remaining link-level files must be developed for input to MOVES. This includes the Links, Link Source Types, and Off Network files. Additional information about these inputs can be found in MOVES User's Guide7.

The Links file contains information about each link in the network to be modeled including a link ID, a county ID, a zone ID, the MOVES road type, the link length, the hourly link volume, the average link speed, the link description, and the average grade of the link. The user must provide data in the Links file for each unique link ID in the operating mode distribution file being used. The link ID should match that used in the operating mode distribution file and the link description can be obtained from Table II-3. The county ID should represent the county of the project being model. The MOVES road type for a signalized arterial scenario would typically be coded as 5, representing an urban unrestricted access road type while the remaining congestion scenarios would be coded as 4 to represent an urban restricted access road type. The link length (in miles) should represent the actual length of the link to be modeled and the link volume should represent the actual hourly volume on the link for the hour being modeled. Even if an operating mode distribution is provided (thus taking calculational precedence over average speeds), the link average speed entered on the Links tab is used in MOVES to compute source hours of operation. It thus needs to be consistent with the information entered in the operating mode distribution tab.  The link average grade can be entered as 0.

The Link Source Type Hour file needs to contain a record for all source types driving on a given link, for all links in the network. The fraction of travel by all source types within the hour being modeled for each link needs to sum to 1.

The remaining required data files needed to perform MOVES runs for a project level analysis include meteorology, age distribution, fuel formulation and supply, and inspection/maintenance programs. These inputs are generally the same as the MOVES inputs that would be required for a county level run, such as for a SIP application, and are likely to have already been developed for the area being studied. However, users should verify each individual input as there may be exceptions (especially for age distribution and fuel formulation and supply). The user should refer to the MOVES users guide for further information on developing these inputs.

Updated: 07/26/2011
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