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United States-Mexico Land Ports of Entry Emissions and Border Wait-Time White Paper and Analysis Template

3.0 Analysis Template Approach

This section provides guidance on how to conduct an emissions analysis for U.S.-Mexico land ports of entry, using an analysis template developed within the context of the El Paso/Juarez border crossing, but for application along the entirety of the U.S.-Mexico border. A flowchart for the approach is provided as Figure 3.1. The process involves developing representative emission rates and then combining those rates with vehicle activity data for all of the scenarios being analyzed. Differences between scenarios can then be quantified by contrasting the results from the emissions analysis. The following sections provide a general description of how emissions are characterized at the El Paso/Juarez ports of entry, the development of emissions factors, identifying and quantifying vehicle activity at the border, and how to combine these data to quantify emissions. The same set of procedures can be adapted for analysis of other ports of entry.

3.1 Development of Emission Factors

This section encapsulates three related steps needed for estimating emissions at a border crossing: defining the types of vehicle behavior or activity that occur at ports of entry, developing emission rates corresponding to those types of activity, and finally compositing of those emission rates into a form that can be applied directly to the border activity.

Defining Vehicle Behavior at Ports of Entry

A detailed analysis of vehicle behavior was conducted through the use of a VISSIM microsimulation model for both Bridge of the Americas and Ysleta-Zaragoza ports of entry. The analysis identified the difference between different types of approach lanes both in terms of the classes of vehicles that use the lane, and the Customs and Border Protection programs serviced by the lanes. Differentiation also was made between northbound and southbound vehicle movements.

Three types of vehicle behavior were selected for detailed analysis. These were defined as:

Figure 3.1 Analysis Template Approach

Figure 3.1 presents a flow chart for how to conduct an emissions analysis of border crossings. Click image for text description.

Source: Cambridge Systematics, Inc.

Table 3.1, Table 3.2, and Table 3.3 summarize the passenger vehicle-specific power (VSP) and commercial vehicle scales tractive power (STP) profiles for use with the MOVES model, and average speeds for use with EMFAC and MOBILE6 Mexico. The VSP profiles consist of the fraction of vehicle activity occurring in the various vehicle modes of operation, for stop-and-go queues, creeping queues, and uncongested movements for use with the U.S. EPA MOVES model (note that each column sums to 1.0). The MOVES operating modes used in this analysis include vehicle deceleration, idling, and cruise/acceleration; with cruise/acceleration broken into low (less than 25 mph), medium (25-50 mph), and high (greater than 50 mph) speeds at varying VSP levels indicative of the engine load. Seven types of lanes are represented in the vehicle activity characterizations: 1) Northbound FAST (Free And Secure Trade (FAST) program where drivers, vehicles, and cargo are pre cleared for entry into the U.S.) trucks, 2) Northbound unladen trucks, 3) Northbound laden trucks, 4) Southbound trucks (all types), 5) Northbound autos, 6) Northbound SENTRI (Secured Electronic Network for Travelers Rapid Inspection (SENTRI) program is a transponder based program providing expedited inspection and clearance through primary inspection via dedicated commuter lanes.) autos, and 7) Southbound autos (all types). Note that data for SENTRI lanes are assumed to represent Ready (Ready lanes provide a dedicated lane for privately owned vehicles entering the U.S. for vehicles whose occupants have WHTI-compliant, RFID-enabled cards approved by the Department of Homeland Security.) lanes as well. In addition the tables provide representative vehicle speeds for use with models such as MOBILE6 Mexico and EMFAC.

There are additional types of vehicle behavior that need to be quantified as the analysis is conducted. These consist of what is referred to as "off-network" vehicle activity within the framework of the MOVES model. Off-network area data include information about vehicles which are not driving on the links or roadways, but still contribute to port-of-entry vehicle emissions while idling, extended idling (Extended idle is used to power accessory loads such as air conditioning when a vehicle is parked.) or starting. In the case of most U.S.-Mexico border crossings, trucks stopping and restarting for inspections are accounted for in the off-network area. As was the case for running emissions, off-network emissions estimates were developed as emission rates (start emissions in gram/start and extended idling in grams per hour) and were generated by soak time (i.e., a specific start emission rate was developed for each specific soak). The soak times available in MOVES include:

More information on the how these activity profiles were developed is provided in the Task 3 technical reports (attached).

Table 3.1 Stop-and-Go Queues
Fraction of Activity by Operating Mode For Use with MOVES, and Average Speed For Use With EMFAC and MOBILE6 Mexico
Empty cell. VSP STP MOVES OpModeID NB FAST Trucks NB Unladen Trucks NB Laden Trucks SB Trucks (All) NB Autos NB SENTRI Autos SB Autos (All)
Deceleration Empty cell. 0 0.229 0.330 0.212 0.266 0.267 0.244 0.203
Idle Empty cell. 1 0.627 0.549 0.659 0.590 0.629 0.597 0.610
Cruise/Acceleration
1 to 25 Miles Per Hour
< 0 11 0.044 0.044 0.042 0.047 0.038 0.055 0.001
Cruise/Acceleration
1 to 25 Miles Per Hour
0-3 12 0.091 0.071 0.075 0.089 0.065 0.095 0.184
Cruise/Acceleration
1 to 25 Miles Per Hour
3-6 13 0.004 0.002 0.003 0.003 0.001 0.002 0.001
Cruise/Acceleration
1 to 25 Miles Per Hour
6-9 14 0.001 0.001 0.002 0.001 0.000 0.002 0.000
Cruise/Acceleration
1 to 25 Miles Per Hour
9-12 15 0.001 0.000 0.001 0.001 0.000 0.001 0.000
Cruise/Acceleration
1 to 25 Miles Per Hour
12+ 16 0.003 0.003 0.005 0.002 0.001 0.003 0.000
Cruise/Acceleration
25 to 50 Miles Per Hour
< 0 21 N/A N/A N/A N/A 0.000 N/A N/A
Cruise/Acceleration
25 to 50 Miles Per Hour
0-3 22 N/A N/A N/A N/A 0.000 N/A 0.000
Cruise/Acceleration
25 to 50 Miles Per Hour
3-6 23 N/A N/A N/A 0.000 0.000 N/A 0.000
Cruise/Acceleration
25 to 50 Miles Per Hour
6-9 24 N/A N/A N/A N/A 0.000 N/A 0.000
Cruise/Acceleration
25 to 50 Miles Per Hour
9-12 25 N/A N/A N/A N/A N/A N/A N/A
Cruise/Acceleration
25 to 50 Miles Per Hour
12-18 27 N/A N/A N/A 0.000 N/A N/A N/A
Cruise/Acceleration
25 to 50 Miles Per Hour
18-24 28 N/A N/A 0.000 N/A 0.000 N/A N/A
Cruise/Acceleration
25 to 50 Miles Per Hour
24-30 29 N/A N/A N/A N/A 0.000 0.000 0.000
Cruise/Acceleration
25 to 50 Miles Per Hour
30+ 30 N/A N/A 0.000 0.000 0.000 0.000 0.000
Cruise/Acceleration
50+ Miles Per Hour
< 6 33 N/A N/A N/A N/A N/A N/A N/A
Cruise/Acceleration
50+ Miles Per Hour
6-12 35 N/A N/A N/A N/A N/A N/A N/A
Cruise/Acceleration
50+ Miles Per Hour
12-18 37 N/A N/A N/A N/A N/A N/A N/A
Cruise/Acceleration
50+ Miles Per Hour
18-24 38 N/A N/A N/A N/A N/A N/A N/A
Cruise/Acceleration
50+ Miles Per Hour
24-30 39 N/A N/A N/A N/A N/A N/A N/A
Cruise/Acceleration
50+ Miles Per Hour
30+ 40 N/A N/A N/A N/A N/A N/A N/A
Average Speed (mph) Empty cell. Empty cell. 1 1 1 1 1 1 1
Table 3.2 Creeping Queues
Fraction of Activity by Operating Mode For Use with MOVES, and Average Speed For Use With EMFAC and MOBILE6 Mexico
Empty cell. VSP STP MOVES OpModeID NB FAST Trucks NB Unladen Trucks NB Laden Trucks SB Trucks (All) NB Autos NB SENTRI Autos SB Autos (All)
Deceleration Empty cell. 0 0.295 0.364 0.294 0.286 0.276 0.259 0.259
Idle Empty cell. 1 0.504 0.439 0.495 0.521 0.525 0.505 0.507
Cruise/Acceleration
1 to 25 Miles Per Hour
< 0 11 0.060 0.071 0.073 0.065 0.073 0.081 0.002
Cruise/Acceleration
1 to 25 Miles Per Hour
0-3 12 0.132 0.118 0.128 0.119 0.119 0.140 0.232
Cruise/Acceleration
1 to 25 Miles Per Hour
3-6 13 0.004 0.004 0.006 0.005 0.004 0.004 0.000
Cruise/Acceleration
1 to 25 Miles Per Hour
6-9 14 0.002 0.002 0.001 0.001 0.002 0.001 0.000
Cruise/Acceleration
1 to 25 Miles Per Hour
9-12 15 0.001 0.001 0.001 0.001 0.001 0.001 0.000
Cruise/Acceleration
1 to 25 Miles Per Hour
12+ 16 0.001 0.001 0.001 0.001 0.001 0.002 0.000
Cruise/Acceleration
25 to 50 Miles Per Hour
< 0 21 0.000 0.000 0.000 0.000 0.000 0.000 N/A
Cruise/Acceleration
25 to 50 Miles Per Hour
0-3 22 N/A 0.000 N/A N/A 0.000 0.001 0.000
Cruise/Acceleration
25 to 50 Miles Per Hour
3-6 23 0.000 0.000 0.000 0.000 0.000 0.001 0.000
Cruise/Acceleration
25 to 50 Miles Per Hour
6-9 24 0.000 0.000 0.000 0.000 0.000 0.001 0.000
Cruise/Acceleration
25 to 50 Miles Per Hour
9-12 25 0.000 0.000 0.000 0.000 0.000 0.000 N/A
Cruise/Acceleration
25 to 50 Miles Per Hour
12-18 27 0.000 0.000 0.000 0.000 0.000 0.000 N/A
Cruise/Acceleration
25 to 50 Miles Per Hour
18-24 28 N/A 0.000 0.000 0.000 0.000 0.000 N/A
Cruise/Acceleration
25 to 50 Miles Per Hour
24-30 29 0.000 N/A 0.000 0.000 0.000 0.001 N/A
Cruise/Acceleration
25 to 50 Miles Per Hour
30+ 30 0.000 0.000 0.000 0.000 0.000 0.000 N/A
Cruise/Acceleration
50+ Miles Per Hour
< 6 33 N/A N/A N/A N/A N/A N/A N/A
Cruise/Acceleration
50+ Miles Per Hour
6-12 35 N/A N/A N/A N/A N/A N/A N/A
Cruise/Acceleration
50+ Miles Per Hour
12-18 37 N/A N/A N/A N/A N/A N/A N/A
Cruise/Acceleration
50+ Miles Per Hour
18-24 38 N/A N/A N/A N/A N/A N/A N/A
Cruise/Acceleration
50+ Miles Per Hour
24-30 39 N/A N/A N/A N/A N/A N/A N/A
Cruise/Acceleration
50+ Miles Per Hour
30+ 40 N/A N/A N/A N/A N/A N/A N/A
Average Speed (mph) Empty cell. Empty cell. 5 5 5 5 5 5 5
Table 3. 3 Uncongested Movement
Fraction of Activity by Operating Mode For Use with MOVES, and Average Speed For Use With EMFAC and MOBILE6 Mexico
Empty cell. VSP STP MOVES OpModeID NB FAST Trucks NB Unladen Trucks NB Laden Trucks SB Trucks (All) NB Autos NB SENTRI Autos SB Autos (All)
Deceleration Empty cell. 0 0.248 0.187 0.206 0.195 0.265 0.153 0.215
Idle Empty cell. 1 0.123 0.111 0.174 0.268 0.297 0.118 0.362
Cruise/Acceleration
1 to 25 Miles Per Hour
< 0 11 0.024 0.027 0.026 0.029 0.040 0.021 0.001
Cruise/Acceleration
1 to 25 Miles Per Hour
0-3 12 0.034 0.028 0.036 0.041 0.053 0.025 0.118
Cruise/Acceleration
1 to 25 Miles Per Hour
3-6 13 0.007 0.008 0.008 0.007 0.010 0.007 0.003
Cruise/Acceleration
1 to 25 Miles Per Hour
6-9 14 0.004 0.006 0.004 0.004 0.005 0.004 0.000
Cruise/Acceleration
1 to 25 Miles Per Hour
9-12 15 0.005 0.005 0.004 0.004 0.002 0.003 0.000
Cruise/Acceleration
1 to 25 Miles Per Hour
12+ 16 0.008 0.010 0.009 0.012 0.005 0.018 0.000
Cruise/Acceleration
25 to 50 Miles Per Hour
< 0 21 0.014 0.016 0.016 0.014 0.012 0.027 0.000
Cruise/Acceleration
25 to 50 Miles Per Hour
0-3 22 0.266 0.327 0.290 0.214 0.037 0.074 0.058
Cruise/Acceleration
25 to 50 Miles Per Hour
3-6 23 0.222 0.226 0.189 0.180 0.213 0.393 0.239
Cruise/Acceleration
25 to 50 Miles Per Hour
6-9 24 0.006 0.010 0.006 0.007 0.051 0.120 0.003
Cruise/Acceleration
25 to 50 Miles Per Hour
9-12 25 0.017 0.016 0.013 0.008 0.005 0.013 0.000
Cruise/Acceleration
25 to 50 Miles Per Hour
12-18 27 0.016 0.019 0.014 0.013 0.001 0.004 0.000
Cruise/Acceleration
25 to 50 Miles Per Hour
18-24 28 0.002 0.002 0.002 0.002 0.001 0.005 0.000
Cruise/Acceleration
25 to 50 Miles Per Hour
24-30 29 0.001 0.001 0.000 0.000 0.001 0.008 0.000
Cruise/Acceleration
25 to 50 Miles Per Hour
30+ 30 0.001 0.001 0.001 0.001 0.001 0.009 0.000
Cruise/Acceleration
50+ Miles Per Hour
< 6 33 N/A N/A N/A N/A N/A N/A N/A
Cruise/Acceleration
50+ Miles Per Hour
6-12 35 N/A N/A N/A N/A N/A N/A N/A
Cruise/Acceleration
50+ Miles Per Hour
12-18 37 N/A N/A N/A N/A N/A N/A N/A
Cruise/Acceleration
50+ Miles Per Hour
18-24 38 N/A N/A N/A N/A N/A N/A N/A
Cruise/Acceleration
50+ Miles Per Hour
24-30 39 N/A N/A N/A N/A N/A N/A N/A
Cruise/Acceleration
50+ Miles Per Hour
30+ 40 N/A N/A N/A N/A N/A N/A N/A
Average Speed (mph) Empty cell. Empty cell. 30 30 30 25 35 35 35

Emission Factors by Vehicle Activity

Emission rates for use with this analysis template can come from various models, including MOVES, EMFAC, or MOBILE6 Mexico, or from rates tabulated as part of this project. Emission rates representing the El Paso/Juarez port of entry are provided in the Task 3 technical support material (attached). Both approaches are discussed below. These approaches produce detailed emission rate information that will subsequently be combined into composite emission rates, through weighted averages. A discussion of the development of composite emission rates is in Section 4.0, which follows this section.

Using MOVES or Related Models to Develop Local Emission Rates

This section presents a discussion of background information and key underlying concepts for project-level emissions analysis using MOVES. The concepts and approaches are also applicable to MOBILE6 Mexico and EMFAC unless noted otherwise. Complete run specification and supporting files for the application of MOVES2010a to the El Paso/Juarez port of entry are provided as part of the electronic archive of supporting material for this white paper and analysis protocol.

The MOVES model represents a significant improvement compared to the MOBILE platform (EPA's previous highway vehicle emission factor model) by giving users the ability to account for variations in vehicle speed and acceleration as well as the vehicle operating mode (e.g., cruise, acceleration, braking, idling) when estimating highway vehicle emissions. Along with these enhanced capabilities comes the need for more detailed inputs, and thus for more underlying data to be collected. Unlike the MOBILE model, MOVES can be run at the project-level scale, which is the focus of this border crossing study. This level of analysis allows users to accurately model areas where travel activity does not follow typical driving patterns. This is the case for border crossings where vehicles typically idle for significant periods of time and also stop and start more frequently than in average traffic conditions.

Base emission rates within MOVES are defined by source bins which are organized by fuel type, regulatory class, age group, and operating mode. The regulatory class is used to define groups of model years that are all subject to the same emission standards and thus, use similar technologies to control emissions. The age groups are used to account for the effects of aging and deterioration of components of the emission control system over time. The MOVES model years associated with each regulatory class are based on U.S. Federal emission standards. However, Mexican emission standards are different from U.S. standards (they are based on a combination of U.S. and European standards). Therefore, using MOVES to estimate emission rates of Mexican vehicles emissions, it is essential to adjust the distribution of vehicles by model year group to account for the difference in U.S. and Mexican emissions standards.

In selecting border crossing data, attention was placed on the parameters that have the greatest influence on vehicle emissions in queuing and congested operating situations. Some of these key variables in MOVES are summarized below.

Vehicle Type

MOVES categorizes vehicles into 13 source types, which are subsets of 6 Highway Performance Monitoring System (HPMS) vehicle classes. Therefore, the characterization of border crossing vehicle data according to FHWA's HPMS classes was a critical step. To best represent the specific vehicle emission rates occurring at these crossings, local information on vehicle volumes by source type or HPMS class is needed. These data also are important in MOBILE6 Mexico and EMFAC.

Vehicle Age and Country of Registration

Vehicle age distributions by vehicle type are important when modeling emissions as these age groups are used to define the emission standards the vehicle was initially certified to meet as well as to account for the effects of deterioration of the emission control components over time. In addition, since vehicles operating in the U.S. and Mexico are subject to different emission standards, the country of registration is important. More detail is provided below on vehicle age and registration data when representing a mix of U.S. and Mexican domiciled vehicles in MOVES.

Within this border crossing analysis, a specific age distribution was developed for the following MOVES source types:

Truck age distribution data were collected in detail for the El Paso/Juarez case study ports of entry, based on Texas Department of Safety (DPS) data (Personal communication between TranSystems and Captain Villarreal; data provided by e-mail, received on 03/21/2012.) (applicability of this age distribution to other regions is available separately). These data included truck make, model year, VIN number, license plate, state or country of registration, and total border crossing count for 2010. These data were provided for the Bridge of the Americas (BOTA) and the Ysleta-Zaragoza Bridge. Although the vast majority of commercial vehicle border crossings are made by trucks registered in Mexico (98.6 percent), separate age distributions were initially developed for U.S. and Mexican trucks. Since the MOVES model incorporates U.S. emissions standards and uses vehicle age to determine which emission standard vehicles were certified to meet, it was important to distinguish trucks complying with different emission standards. Age also is used by the model to estimate deterioration effects. Mexican truck age distributions need to be modified to account for the difference in emission standards between the U.S. and Mexican domiciled vehicles of the same model year. Mexican diesel engine emission standards were aligned with the U.S. EPA standards for the 1994 to 2003 model years. However, Mexico has not revised its emission standards to reflect recent U.S. standards, which require a significant reduction in NOx for 2004-2007 engines and a further decrease in NOx and particulate matter (PM) for 2007+ model-year engines. Essentially, pre-1994 and post-2004 Mexican trucks have higher emissions than American trucks with the same model year due to less stringent standards. For these age groups, the age distribution of Mexican trucks were shifted to make trucks "artificially older" and account for their higher emissions.

For case-study passenger vehicles, a combined age distribution was developed (that includes both Mexican and U.S. vehicles) by using a mix of 50 percent of U.S.-registered and 50 percent of Mexico-registered passenger vehicles (Personal communication between TranSystems and Said Larbi-Cherif, director of El Paso's International Bridge Division (03/19/2012); these numbers are also confirmed by a 1995 study of the El Paso Border Crossing by the El Paso MPO, which estimated that 47.3 percent of cars crossing the border were registered in the U.S. and 52.7 percent were registered in Mexico.). Since no border crossing data were readily available, the El Paso County vehicle type age distribution developed by the Texas Council for Environmental Quality (TCEQ) for their On-Road Mobile Source MOVES Emissions Inventory was used. For passenger vehicles registered in Mexico, an age distribution was developed from model year data provided for the Mexico City passenger vehicle fleet, which was available from a 2004 International Sustainable Systems Research Center (ISSRC) study (International Sustainable Systems Research Center (2004); Mexico City Vehicle Activity Study.). As described for trucks, since Mexican passenger car emission standards are different from U.S. emission standards, it was important to adjust the ISSRC (Mexican passenger vehicle) age distribution to account for the differences in emission standards. The first emission standards for light-duty vehicles became effective in model year 1993 and were later strengthened, effective 2001. A mix of U.S. Tier 1/2 and Euro 3/4 standards is required since 2004. As was the case with heavy-duty vehicles, Mexico has not revised its light-duty emission standards to reflect Tier 2 U.S. standards which require a significant reduction in NOx and PM. Therefore, the age distribution of Mexican cars for those age groups (pre-1993 and post-2007) was shifted to make them "artificially older" and account for higher emissions.

Operating Mode

MOVES includes operating mode bins that categorize vehicle operations by three key operating characteristics: 1) Mode (braking, idle, cruise, acceleration, and coasting), 2) Vehicle-Specific Power (VSP), and 3) Speed. Operating mode distributions, such as those tabulated in the preceding section, coupled with MOVES are the most accurate way of describing vehicle activity. Average speed can be used as a surrogate where alternate models such as MOBILE6 Mexico and EMFAC are being used.

Fuel Formulation and Supply

Fuel formulation defaults for all U.S. counties are available in the MOVES database but new formulations can be calculated with different fuel properties. A comparison of the El Paso fuel formulations and Mexican fuel standards indicated that sulfur contents in both gasoline and diesel are similar since 2007 (the El Paso defaults are again based on the TCEQ on-road MOVES Emissions Inventory). Additionally, the on-road diesel Material Safety Data Sheet provided by PEMEX (Petróleos Mexicanos) also indicated that diesel sold in Mexico is ultralow-sulfur with a maximum sulfur content of 15 parts per million (ppm). Therefore, the MOVES fuel inputs developed to model the El Paso border crossing did not include any differences in the sulfur content of U.S. and Mexican fuel. However, it is important to note that despite these Mexican standards and Safety Data Sheets, ultra-low-sulfur diesel (15 ppm sulfur) is still unavailable throughout most of Mexico. It is supposed to be available in the border region – a border wide swath of about 100 km on either side of the border – and in the three major cities: Mexico City, Monterrey and Guadalajara, but it is not clear that it is in fact available throughout the entire border region. The delays in providing ultra-low-sulfur diesel nationally may have a number of negative consequences including: impeding Mexico's opportunities for significant emissions reductions from diesel vehicles (since new emissions control systems such as DPFs require ultra-low-sulfur diesel to properly function); preventing improved public health; and reducing growth in the manufacture and sale of new clean vehicles within Mexico. Maximum savings through improved fuel efficiency may not be achieved and emissions standards comparable to those in place in the U.S., which would contribute to a smooth transition to long-haul cross-border trade, might not be implemented. Furthermore, U.S. 2007 model year and later trucks traveling into Mexico would be unable to be properly fueled, other than in the border region, Mexico City, Monterrey and Guadalajara, thus posing an additional obstacle to trade.

A comparison of the gasoline Reid vapor pressure (RVP) for U.S. and Mexican fuels showed a significant difference during summer months (aromatic content and benzene are also different). This RVP difference is important as a higher RVP in the Mexican fuel will lead to higher VOC emissions in the summer. Thus, a specific fuel formulation was created for Mexico in the MOVES emission factor modeling.

To properly model emissions, it is important to know how much U.S. and Mexican fuel is used; especially important for summer months, since fuel RVP is different in the two countries. For trucks, it was assumed that 78.1 percent of the fuel is purchased in Mexico. This number was based on a 2008 study from the Institute of Transportation Studies at the University of California, Davis (Nicholas Lutsey (2008) Assessment of Out-Of-State Heavy-Duty Truck Activity Trends in California, Institute of Transportation Studies, University of California, Davis, UCD ITS RR 08 16.). This report provides information regarding the last fueling location of trucks registered in Mexico, which are the vast majority at the El Paso border crossings. Given that this information was not available for passenger vehicles, it was assumed that passenger vehicle owners purchase fuel in their respective country of registration. These are reasonable assumptions to apply for screening level analysis at most locations; however if location-specific data can be obtained it should be used.

As for the distribution of fuel technology (i.e., gasoline versus diesel vehicles), the 2005 Texas Transportation Institute (TTI) study (Texas Transportation Institute (2005); Mexican Truck Idling Emissions at the El Paso-Ciudad Juarez Border Location (SWUTC/05/473700-00033-1).) provided fuel information used to create a MOVES Alternative Vehicle Fuels and Technologies (AVFT) input for truck fuel fractions (an AVFT input can be developed to modify the MOVES default fuel fractions for the vehicles in the project area). According to the ISSRC study (2004 data collected in Mexico City), 0.6 percent of passenger vehicles were diesel. Based on the 0.6 percent value and the El Paso County light-duty diesel fraction, a MOVES AVFT input for passenger vehicle fuel fractions was created. This input can be replicated as a default across other POEs, but location-specific data is preferred.

Inspection and Maintenance (I/M) Program

The presence or absence of an I/M program significantly effects fleet-average emissions for vehicles subject to the program. In Texas, all gasoline-fueled vehicles between 2 and 24 years of age are required by law to be inspected annually if they are registered or operate primarily in participating counties. These include gasoline passenger vehicles, light-commercial trucks, and single-unit short-haul trucks.

In 2007, El Paso County implemented a two-speed idle (TSI) test and an on-board diagnostic (OBD) test. To develop the I/M program MOVES inputs, the El Paso County input which was developed by the TCEQ for their emissions inventory was used. The municipality of Juarez, Mexico also implemented an Inspection and Maintenance program starting in 1994. However, the compliance rate has been noticeably low with a historical average of about 20 percent and a 2010 compliance rate of 44.81 percent (Ciudad Juárez (2011), Dirección General De Ecología Y Protección Civil, Programa de verificación vehicular de emisiones para el Municipio de Juárez 2011-2013.).

Vehicles in Juarez also are required by law to be inspected annually to verify that they meet the maximum emission levels stipulated in the Mexican norm NOM-041-SEMARNAT-2006. The inspection consists of a series of three tests:

For model years 1996+, an OBD test is performed.

A "combined" I/M program was developed for passenger vehicles, which reflects both the U.S. and Mexican programs. To do so, inspection procedures and model-year applicability were compared. To create a combined I/M program input, the El Paso County input developed by the TCEQ and adjusted compliance ratios to account for a smaller participation of Mexican vehicles were used. For future years, the estimated compliance ratio for Mexican vehicles was adjusted since the Juarez Inspection and Maintenance program plan has a goal of reaching a 90 percent compliance rate by 2012. This exercise can be applied utilizing the MOVES or EMFAC models as needed for other POEs along the U.S./Mexican border.

Using Emission Rates Provided in Spreadsheet Tabulations

Spreadsheets containing detailed MOVES2010a emission rates for each of eight pollutants modeled for this analysis template specific to the El Paso/Juarez port of entry are provided with the supplementary electronic data accompanying this report. A separate spreadsheet was developed for each of the eight pollutants analyzed. These include:

Each of these spreadsheets includes emission rates for six different modes of travel activity, each of which is modeled on a separate tab. The six travel activity modes are defined as follows:

The emission rates on each spreadsheet tab are further identified by fuel type (either gasoline or diesel powered vehicles), season (summer or winter operating conditions), and daily time period (a.m., midday, p.m., and overnight).

For privately-owned vehicles, separate emission rates are provided for northbound and southbound movements. SENTRI lanes are listed separately from general purpose POV lanes. For commercial vehicles, separate emission rates are provided for northbound laden trucks, northbound unladen trucks, northbound trucks using FAST program lanes, and southbound movements.

Note that the emission rate tables report zero emission rates where vehicle activity for a given situation is assumed not to exist. For example, buses are assumed to be diesel powered, so emission rates for gasoline powered buses report zero emissions.

Composite Emission Rates

Composite emission rates can be generated by taking weighted averages with respect to time of day, fuel type, and vehicle class.

Case-specific time-of-day activity profiles for vehicles crossing the Ysleta-Zaragoza port of entry are provided in Table 3.4. The day is broken up into morning and afternoon peak-periods, midday, and overnight. The bridge currently is open 24 hours per day for private vehicles and from 6 a.m. to midnight (Monday-Friday) for commercial vehicles. POE hours of operation are location specific and these data need to be estimated for application at other locations. The percentage of vehicle activity in each portion of the day is provided for the seven crossing types that are considered in this analysis template. Each column of data sums to 100 percent. Application of these weighting factors allows the study to focus on daily activity rather than period-specific activity. Some sensitivity regarding the length and delay is lost when using daily statistics rather than peak-period statistics for queue length and delay; therefore aggregating across the entire day needs to be considered on a case-by-case basis.

Diesel fractions for each vehicle class are provided in Table 3.5. These represent an equal weighting of U.S. and Mexican domiciled passenger vehicles and predominantly Mexican trucks (98.6 percent). Each row of data in the table sums to 100 percent. Intercity buses are assumed to be 100 percent diesel. Application of these weighting factors simplifies the analysis by allowing the study to focus on vehicle classes as a whole.

Table 3.4 Case-Specific Distribution of Activity by Time of Day for Calculating Composite Emission Rates
Empty cell. Northbound FAST Trucks Northbound Unladen Trucks Northbound Laden Trucks Southbound Trucks (all) Northbound Passenger Vehicles Northbound SENTRI Vehicles Northbound Passenger Vehicles
6-9 a.m. 8% 20% 3% 8% 11% 11% 11%
9 a.m.-4 p.m. 44% 49% 42% 44% 38% 38% 38%
4-7 p.m. 23% 16% 26% 23% 16% 16% 16%
7 p.m.-6 a.m. 25% 16% 29% 25% 35% 35% 35%

Source: Supporting data collected from Customs and Border Protection (CBP), City of El Paso toll bridges, and traffic counts that were used to develop the Cambridge Systematics El Paso Regional Ports of Entry Operations Plan for the Texas Department of Transportation (2011).

Table 3.5 Case-Specific Diesel Fractions to Use for Calculating Composite Emission Rates
Vehicle Type Gasoline Fraction Diesel Fraction
Passenger Car (Passenger car and passenger truck diesel fractions were calculated based on 50 percent of U.S. diesel fraction (default MOVES data) and 50 percent of Mexican diesel fraction (0.6 percent) (International Sustainable Systems Research Center. Mexico City Vehicle Activity Study (2004)).) 99.51% 0.49%
Passenger Truck (Passenger car and passenger truck diesel fractions were calculated based on 50 percent of U.S. diesel fraction (default MOVES data) and 50 percent of Mexican diesel fraction (0.6 percent) (International Sustainable Systems Research Center. Mexico City Vehicle Activity Study (2004)).) 98.54% 1.46%
Light Commercial Truck (Light commercial trucks default MOVES diesel fractions were used.) 89.47% 10.53%
Intercity Bus (All buses are assumed to be diesel, which is the MOVES default and is consistent with Mexican trends.) 100.00% 0.00%
Single Unit Short-Haul Truck (Single and combination unit truck diesel fractions were derived by fuel type data collected by a Texas Transportation Institute study (TTI) (Extended idle is used to power accessory loads such as air conditioning when a vehicle is parked.) and the ratio of single to combination unit trucks assumed by MOVES. All of the gasoline trucks from the TTI study were assumed to be single unit trucks. (All buses are assumed to be diesel, which is the MOVES default and is consistent with Mexican trends.) 9.38% 90.63%
Combination Short-Haul Truck (Single and combination unit truck diesel fractions were derived by fuel type data collected by a Texas Transportation Institute study (TTI) (Extended idle is used to power accessory loads such as air conditioning when a vehicle is parked.) and the ratio of single to combination unit trucks assumed by MOVES. All of the gasoline trucks from the TTI study were assumed to be single unit trucks. (All buses are assumed to be diesel, which is the MOVES default and is consistent with Mexican trends.) 0.00% 100.00%

Vehicle type distributions for privately owned vehicles and commercial vehicles are provided in Table 3.6. Application of these factors allows the analysis to focus on the type of lane/activity being analyzed, rather than replicating the calculations for individual vehicle classes. The values in Table 3.6 sum to 100 percent for privately owned vehicles, and sum to 100 percent for commercial vehicles.

Table 3.6 Case-Specific Vehicle Type Distribution for Calculating Composite Emission Rates
Crossing Type Vehicle Type Fraction
Privately Owned Vehicles (Derived from Texas Commission on Environmental Quality Data (Texas Commission on Environmental Quality. Development and Production of Statewide, Nonlink-Based, On-Road Mobile Source MOVES Emissions Inventories. Prepared by the Texas Transportation Institute (2011).) and National Institute of Ecology in Mexico data (National Institute of Ecology in Mexico. Mobile Source Emission Estimates Using Remote Sensing Data from Mexican Cities(2009).).) Passenger Cars 79.6%
Privately Owned Vehicles (Derived from Texas Commission on Environmental Quality Data (Texas Commission on Environmental Quality. Development and Production of Statewide, Nonlink-Based, On-Road Mobile Source MOVES Emissions Inventories. Prepared by the Texas Transportation Institute (2011).) and National Institute of Ecology in Mexico data (National Institute of Ecology in Mexico. Mobile Source Emission Estimates Using Remote Sensing Data from Mexican Cities(2009).).) Passenger Trucks 20.4%
Commercial Vehicles Derived from data collected by a Texas Transportation Institute study (TTI) (Texas Transportation Institute Mexican Truck Idling Emissions at the El Paso-Ciudad Juarez Border Location. SWUTC/05/473700-00033-1 (2005).) Light Commercial Truck 11.0%
Commercial Vehicles Derived from data collected by a Texas Transportation Institute study (TTI) (Texas Transportation Institute Mexican Truck Idling Emissions at the El Paso-Ciudad Juarez Border Location. SWUTC/05/473700-00033-1 (2005).) Single Unit Truck 30.3%
Commercial Vehicles Derived from data collected by a Texas Transportation Institute study (TTI) (Texas Transportation Institute Mexican Truck Idling Emissions at the El Paso-Ciudad Juarez Border Location. SWUTC/05/473700-00033-1 (2005).) Combination Unit Trucks 58.7%

The case studies will walk through application of these weighting factors to produce composite emission rates.

3.2 Identify and Quantify Vehicle Activity

Ports of entry can be subdivided into four different types of activity: private vehicles (northbound, southbound), and commercial vehicles (northbound, southbound). At larger ports of entry these four activities may be at physically different locations, whereas lower volume facilities may combine aspects of the private and commercial vehicle crossings; where that's the case the process laid out below can be simplified somewhat.

Northbound Commercial Vehicle Activity

A key for organizing northbound commercial truck activity can be found in Table 3.7. There are three distinct jurisdictions that control different parts of the border crossing: the Mexican government to the south; the U.S. government to the north; and a Texas Department of public safety inspection area the commercial vehicles need to pass through before they are released into the United States. Each jurisdiction operates a variety of processes that the commercial vehicles must pass through (i.e., entrance gates, cargo inspection, and exiting gates). Each of those processes include a mix of vehicle activity (i.e., creeping queues, stop-and-go queues, idle, engine restarts, etc.) associated with it.

Table 3.7 provides a matrix of these vehicle activities that can be associated with each process for the given jurisdictions, broken out by laden, unladen, and FAST trucks. Generally the matrix does not differ by truck type, but there are important differences in some cases. For example unladen trucks are typically not directed into the cargo inspection area operated by U.S. Customs and Border Protection; whereas laden trucks, that are not part of the FAST program, are all routed through cargo inspection.

When classifying activity associated with each process, consideration of both the physical layout and key relationships between different processes needs to be considered. Building on the example from the last paragraph, at the U.S. secondary inspection area laden trucks will experience creeping queues as they move within the facility, idle time as they wait for their designated cargo scan, and park/restart process to accommodate the scan itself. In contrast unladen and FAST trucks will simply creep to the exit booth (where the FMCSA safety inspection takes place.)

Northbound Private Vehicle Activity

Table 3.8 is the matrix of vehicle activity by process of jurisdiction for northbound privately owned vehicles. Activity needs to be quantified for each type of lane that will be included in the emissions analysis. For example SENTRI lanes need to be broken out from general purpose lanes. Buses tend to have a unique operating pattern; they approach the U.S. primary inspection point, passengers disembark and are cleared independently of the bus, and then board buses on the U.S. side of the border (often not the same bus). Once the bus crosses the border it picks up passengers who have been cleared for entry into the U.S., often these passengers would have arrived at the border on one of the preceding buses.

Table 3.7 Identifying Northbound Commercial Truck Activity
Empty cell. Laden Unladen FAST
Mexican
Toll Collection (If no toll collection queues extend to next step in the border crossing process.) Uncongested movement
Creeping queue
Stop-and-go queue
Idle
Uncongested movement
Creeping queue
Stop-and-go queue
Idle
Uncongested movement
Creeping queue
Stop-and-go queue
Idle
Mexican Export Customs Entrance Creeping queue
Idle
Creeping queue Idle Creeping queue Idle
Mexican Export Inspection (Typically less than 10 percent of fleet, assume one hour park to physically inspect cargo.) Creeping queue
Park for one hour (if inspected)
Creeping queue
Park for more than six minutes (if inspected)
Creeping queue
Mexican Customs Exit Inspection Idle Idle Idle
U.S.
U.S. Customs Primary Inspection Uncongested movement
Creeping queue
Stop-and-go queue
Idle
Uncongested movement
Creeping queue
Stop-and-go queue
Idle
Uncongested movement
Creeping queue
Stop-and-go queue
Idle
U.S. Secondary Inspection (Unladen trucks are scanned as they exit the primary booth; FAST trucks assumed not to go to secondary; Laden trucks sent to secondary where the driver exits the vehicle: average park of less than 6 minutes for VACIS/Eagle Inspections (analogous to an x-ray) and 6-30 minutes for the Gantry scanner (analogous to a CAT scan).) Creeping queue
Idle
Distance of park time and restart
Creeping queue Creeping queue
U.S. Customs Exit Inspection Idle Idle Idle
State of Texas
Texas DOT Safety Inspection Creeping queue
Idle
Creeping queue
Idle
Creeping queue
Idle
Exit POE Uncongested movement Uncongested movement Uncongested movement
Table 3.8 Identifying Northbound POV Activity
Empty cell. General Purpose SENTRI Bus
Mexican
Toll Collection Uncongested movement
Creeping queue
Stop-and-go queue
Idle
Uncongested movement
Creeping queue
Stop-and-go queue
Idle
Uncongested movement
Creeping queue
Stop-and-go queue
Idle
U.S.
U.S. Customs Primary Inspection Uncongested movement
Creeping queue
Stop-and-go queue
Idle
Uncongested movement
Creeping queue
Stop-and-go queue
Idle
Uncongested movement
Creeping queue
Stop-and-go queue
Idle
U.S. Secondary Inspection Park if inspected N/A N/A

Southbound Vehicle Activity

Table 3.9 provides a matrix of vehicle activity by process and jurisdiction for southbound commercial vehicles, and Table 3.10 is a matrix for southbound privately owned vehicles. Southbound commercial and private vehicle traffic may be combined until just prior to crossing the border, or all the way up to inbound cargo inspection for Mexico.

Table 3.9 Identifying Southbound Truck Activity
Empty cell. All Trucks
U.S.
Toll Collection Uncongested movement
Creeping queue
Stop-and-go queue
Idle
U.S. Customs Outbound Inspection Uncongested movement
Creeping queue
Stop-and-go queue
Idle
Mexican
Mexican Customs Primary Inspection Uncongested movement
Creeping queue
Stop-and-go queue
Idle
Mexican Customs Secondary Inspection Park if inspected
Mexican Customs Exit Inspection Creeping queue
Idle
Table 3.10 Identifying Southbound POV Activity
Empty cell. General Purpose Bus
U.S.
U.S. Customs Outbound Inspection Uncongested movement
Creeping queue
Stop-and-go queue
Idle
Uncongested movement
Creeping queue
Stop-and-go queue
Idle
Toll Collection (If no toll collection queues extend to next step in the border crossing process.) Stop-and-go queue
Idle
Stop-and-go queue
Idle
Mexican
Mexican Customs Primary Inspection Uncongested movement
Creeping queue
Stop-and-go queue
Idle
Uncongested movement
Creeping queue
Stop-and-go queue
Idle
Mexican Customs Secondary Inspection Park if inspected
Idle
N/A

3.3 Combine Data to Quantify Emissions

After the matrices of vehicle activity data and the composite emission factors are available it is a simple matter to multiply through all combinations of vehicle activity with the corresponding emission rates to produce the emissions inventory. Typically several emission inventories need to be developed, one for no-action scenario (or a baseline), and one for each of the management/policy/investment strategies to be analyzed. Once emission inventories are available they can be compared and contrasted to identify the emission impacts of the strategies being considered.

Results are often presented in a bar graph which allows the audience to visualize the differences and see relationships between strategies over time where multiple years are being analyzed.

Updated: 12/03/2012
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