HERS-ST Highway Economic Requirements System - State Version: Technical Report
Appendix F Procedures for Estimating Air Pollution Costs
F.1 Overview
HERS calculates the monetary value of damages from air pollution generated by motor vehicles using a sample section under "baseline" conditions during each funding period, and with each candidate improvement to that sample section. Air pollution costs under baseline or improved travel conditions on a section depend upon three factors: (1) HERS' estimates of average daily traffic volume on the section during each funding period; (2) the mix of vehicle classes that typically use facilities of the type represented by the sample section; and (3) HERS' estimates of the average effective speed (AES) of travel on the section during each future funding period. Figure F-1 illustrates the process used to calculate air pollution costs for a sample section under each set of travel conditions.1
Differences in air pollution costs between baseline or unimproved travel conditions - including daily traffic volume and average effective speed - and conditions with an improvement in place are included in HERS' calculation of the net benefits from implementing that improvement. Reductions in air pollution costs increase the net benefits from an improvement; while an increase in the air pollution costs generated by the travel volume and speed estimated to result from an improvement reduce its net benefits. Changes in air pollution costs resulting from an improvement's effect on travel conditions on a sample section increase or reduce the benefits from making that improvement during all funding periods comprising its lifetime.
F.1.1 How Improvements Affect Air Pollution Costs
Differences between baseline travel conditions and conditions with an improvement in place can cause total air pollutant emissions from vehicles traveling on a section to change for two reasons. First, the per-mile rates at which motor vehicles emit some pollutants vary with travel speed, and can rise or decline in response to the increase in average speed on a sample section that results from an improvement. Second, average daily traffic and thus total vehicle-miles of travel on a section increases from its baseline level under improved conditions due to the response of travel demand to the increase in average travel speed on the section.
By increasing the volume of travel on a section, a candidate improvement increases air pollutant emissions and their resulting costs, since these costs are assumed to depend directly on total emissions. At the same time, the increase in average travel speed on the segment can reduce emissions per vehicle-mile of some pollutants, thus offsetting some or all of the effect of higher travel volumes on total air pollution costs. However, particularly large speed increases can actually cause per-mile emission rates of some pollutants to rise, thereby "magnifying" the increase in air pollution costs from higher travel volumes. Thus total air pollution costs resulting from travel on a HERS sample section can either rise or fall as the result of an improvement.
1. The broad outline for these procedures was developed by Apogee Research under contract to the Federal Highway Administration, and is documented in the report Procedures for Incorporating Air Pollution Effects in the HERS Model for National Highway Investment Analysis, September 1996.
Figure F-1. Overview of HERS Procedure for Estimating Air Pollution Costs
F.1.2 Critical Assumptions
Differences in air pollutant emissions generated by changes between baseline and improved travel conditions are assumed to contribute directly to changes in atmospheric concentrations of those pollutants. In turn, the total costs of damages to human health and property from air pollution are assumed to vary in response to changes in these atmospheric concentrations. Thus potential improvements to a HERS sample section are assumed to alter total air pollution damage costs in exact proportion to any change in pollutant emissions generated by vehicles traveling on the section that results from an improvement. HERS uses widely-accepted estimates of the dollar value of health and property damages caused per ton of each major pollutant to calculate air pollution costs from travel on sample sections under baseline and improved conditions.
Because the air pollution cost estimates used by HERS represent nationwide averages for dollar damages to human health and property caused by individual pollutants, they reflect the exposure of residents and property to air pollution that occurs at typical U.S. population and development densities. For pollutants that tend to remain concentrated near their original source, HERS scales these average per-ton damage costs upward to reflect the greater population and property exposure to emissions of those pollutants from vehicles using sample sections located in urban areas. Conversely, HERS scales these nationwide average damage costs downward to reflect the lower population and development densities that typically surround sample sections located outside urban areas. For pollutants that tend to disperse widely, HERS applies nationwide average damage costs per ton of emissions generated by travel on both urban and non-urban sample sections.
HERS estimates the changes in costs from air pollution damages that would result from all candidate improvements to a sample section during the current and each future funding period. Because the per-mile rates at which motor vehicles emit most air pollutants are expected to decline throughout the time horizon considered by HERS, air pollution costs on most sample sections are expected to fall throughout the foreseeable future under both baseline and improved travel conditions. As a result, differences in air pollution costs between baseline and improved conditions - and thus the changes in air pollution costs that HERS includes among the benefits or disbenefits resulting from candidate improvements - are expected to decline during each successive future funding period considered by the model.
F.2 Estimating Air Pollutant Emissions
F.2.1 Specific Pollutants Considered
Motor vehicles' contribution to air pollution consists partly of tailpipe emissions of four commonplace pollutants that can accumulate in unhealthful concentrations in the earth's atmosphere: carbon monoxide (usually abbreviated CO), sulfur oxides (SOx), nitrogen oxides (NOx), and particulate matter less than 2.5 microns in diameter (PM2.5). Under certain conditions, nitrogen oxides also combine in the atmosphere with other chemical compounds emitted by motor vehicles (among other sources) to form ground-level ozone.2 Atmospheric levels of airborne dust, another pollutant that can be harmful to human health and property when it reaches certain concentrations, are also increased as moving vehicles' tires contact road pavement surfaces.
2. These "volatile organic compounds" (VOC) are emitted from the tailpipes of gasoline-powered vehicles, as well as by the evaporation of gasoline during vehicle refueling, storage, and operation.
F.2.2 Emission Rates for HERS Vehicle Classes and Section Types
Different types of motor vehicles emit each of these six pollutants at varying rates per mile of travel. Vehicles' emission rates depend on the type of fuel used (gasoline or diesel), engine size, and vehicle weight, as well as on operating conditions such as ambient temperature, road grade, and altitude. Emission rates for some pollutants - principally carbon monoxide, volatile organic compounds, and nitrogen oxides - also vary with vehicles' average operating speeds, while others (sulfur oxides, particulate matter, and road dust) are approximately constant regardless of speed. In addition, emission rates for individual vehicle classes can vary among different roadway types even for travel at the same average speed, because the characteristic patterns of acceleration, braking, and cruising that produce a given average speed differ among major roadway classes, such as freeways, arterials, and collectors.
Each of the nine section types utilized by HERS, which are differentiated by location (urban vs. rural) and functional class (expressway, arterial, collector) tends to be used by a characteristic mix of vehicle types. Differing vehicle mixes reflect the varying combinations of travel purposes served by different road and highway facilities, together with the common use of specific types of vehicles to provide different types of transportation services. Table F-1 reports the characteristic distribution of total vehicle-miles traveled among the seven detailed vehicle classes employed by HERS for each of its nine different roadway section types.
Emission rates for each HERS vehicle class operating on different types of roadways were first estimated for the various pollutants using models developed by the U.S. Environmental Protection Agency (EPA). These rates measure average emissions per vehicle-mile of travel on freeway, arterial, and collector sections for each of the six air pollutants whose damage costs are considered by HERS. The MOBILE6 motor vehicle emission factor model was used to estimate average emissions per vehicle-mile of travel at different average speeds for carbon monoxide (CO), volatile organic compounds (VOCs), and oxides of nitrogen (NOx) as functions of average travel speed and roadway type.3 The EPA's vehicle emission factor model for particulate pollutants, PART5, was used to estimate average emissions per vehicle-mile of sulfur oxides (SOx), small particulate matter (PM-10), and road dust generated by individual vehicle classes operating on each HERS section type.4 Emissions of these pollutants are assumed by PART5 to be independent of vehicle operating speeds. Both emission models' "default" assumptions regarding the age distribution of the U.S. vehicle fleet and operating conditions such as typical fuel composition, ambient temperatures, and altitude were employed in developing these estimates.
Developing these emission rates required detailed "mapping" of the distribution of vehicle travel among the seven detailed vehicle classes employed by HERS into the different vehicle classification systems employed by MOBILE6 (which employs 16 separate vehicle types) and PART5 (12 vehicle types). This was accomplished using extremely detailed data on travel by vehicle type, weight, and roadway class derived from the HPMS system, which were provided by FHWA's Office of Highway Policy Information. These data were employed as an intermediate or "translating" stage between the vehicle classification systems used by HERS and each of the two emission factor models, in conjunction with detailed descriptions of the weight ranges and physical characteristics of vehicles used by HERS, MOBILE6, and PART5 to classify vehicles. Table F-2 and Table F-3 show the relationships between HERS' seven detailed vehicle classes and the vehicle classes employed by the MOBILE6 and PART5 emission factor models.
3. For a brief description of the structure of the MOBILE model, see The MOBILE Model and Transportation Planning, Report FHWA-PD-96-005, Federal Highway Administration, September 1995. Complete documentation of MOBILE is available at http://www.epa.gov/otaq/m6.htm
4. The PART5 model is described in An Overview of PM-10 Base Year Emission Inventories, Report FHWA-PD-98-002, Federal Highway Administration, November 1997.
| Section Type | Four Tire Vehicles | Single Unit Trucks | Combination Trucks | |||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Small Autos | Med/Lg Autos | Pickups & Vans | All Four Tire Vehicles | Six-Tire Trucks | 3 + Axle SUTs | All Single Unit Trucks | 3 - 4 Axles | 5 or More Axles | All Combination Trucks | |
| OPA indicates Other Principal Arterials. | ||||||||||
| Source: Estimated by Volpe Center from 1999 HPMS data on VMT by vehicle type and functional class supplied by FHWA Office of Highway Policy Information. | ||||||||||
| Rural Interstate | 28.4% | 34.2% | 37.3% | 100.0% | 83.9% | 16.1% | 100.0% | 7.4% | 92.6% | 100.0% |
| Rural OPA* | 26.9% | 32.4% | 40.8% | 100.0% | 79.6% | 20.4% | 100.0% | 9.4% | 90.6% | 100.0% |
| Rural Minor Arterial | 26.7% | 32.2% | 41.1% | 100.0% | 79.2% | 20.8% | 100.0% | 11.7% | 88.3% | 100.0% |
| Rural Major Collector | 25.7% | 31.0% | 43.3% | 100.0% | 77.5% | 22.5% | 100.0% | 12.3% | 87.7% | 100.0% |
| Urban Interstate | 30.4% | 36.9% | 32.7% | 100.0% | 81.5% | 18.5% | 100.0% | 9.2% | 90.8% | 100.0% |
| Urban Other Fwy/ Exwy | 31.4% | 38.1% | 30.5% | 100.0% | 82.1% | 17.9% | 100.0% | 12.4% | 87.6% | 100.0% |
| Urban OPA* | 29.5% | 35.7% | 34.7% | 100.0% | 80.8% | 19.2% | 100.0% | 16.6% | 83.4% | 100.0% |
| Urban Minor Arterial | 30.1% | 36.4% | 33.6% | 100.0% | 73.5% | 26.5% | 100.0% | 26.5% | 73.5% | 100.0% |
For the three speed-sensitive pollutants, emission rates for each of the seven detailed vehicle classes and nine section types employed by HERS were estimated at speeds ranging from 5 to 70 mph in 5-mph increments. The measure used by the MOBILE6 emissions factor model to adjust individual vehicle types' emission rates for speed variation represents the average operating speeds for several different "driving cycles" that combine different phases of vehicle operation (acceleration, cruising, braking, and idling) in varying proportions.5 The specific driving cycles used to test variation in different vehicle classes' emission rates are intended to represent typical trips that specific types of vehicles are commonly used to make, and that result in different overall average speeds. This measure of travel speed is broadly consistent with the average effective speed (AES) measure employed by HERS, which is intended to represent the average speed of travel on a section associated with its predicted daily travel volume, assuming a characteristic mix of vehicle classes and distribution of travel between peak and off-peak periods for that section type.
5. Emissions for a sample of vehicles are measured on each of these driving cycles, and expressed relative to those measured for the test cycle used to certify their compliance with prevailing federal emission standards. The resulting "speed correction factors" are used to estimate vehicles' emissions when driven at speeds other than the approximately 20 mph average of the certification test cycle.
| MOBILE6 Vehicle Class | Proportion of MOBILE6 Vehicle Class Included in HERS Vehicle Class: | ||||||
|---|---|---|---|---|---|---|---|
| Small Autos | Medium/Large Autos | Pickups & Vans | Six-Tire Trucks | 3+ Axle SUTs | 3-4 Axle Combos | 5+ Axle Combos | |
| All Classes | 1.0000 | 1.0000 | 1.0000 | 1.0000 | 1.0000 | 1.0000 | 1.0000 |
| Source: Estimated by Volpe Center from 1999 HPMS data on VMT by vehicle type and functional class supplied by FHWA Office of Highway Policy Information. | |||||||
| LDGV | 0.9991 | 0.9179 | |||||
| LDDV | 0.0009 | 0.0008 | |||||
| LDGT1 | 0.0813 | ||||||
| LDGT2 | 0.6835 | ||||||
| LDGT3 | 0.2142 | ||||||
| LDGT4 | 0.0984 | ||||||
| LDDT34 | 0.0040 | ||||||
| HDGV2B | 0.8002 | ||||||
| HDDV2B | 0.1998 | ||||||
| HDGV3 | 0.1778 | ||||||
| HDDV3 | 0.3733 | ||||||
| HDGV4 | 0.0284 | ||||||
| HDDV4 | 0.1756 | ||||||
| HDGV5 | 0.1311 | ||||||
| HDDV5 | 0.1138 | ||||||
| HDGV6 | 0.1689 | ||||||
| HDDV6 | 0.2876 | ||||||
| HDGV7 | 0.0781 | ||||||
| HDDV7 | 0.4654 | ||||||
| HDGV8A | 0.0001 | ||||||
| HDDV8A | 0.1606 | ||||||
| HDGV8B | 0.0000 | ||||||
| HDDV8B | 0.8393 | ||||||
| PART5 Vehicle Class | Proportion of PART5 Vehicle Class Included in HERS Vehicle Class: | ||||||
|---|---|---|---|---|---|---|---|
| Small Autos | Medium/Large Autos | Pickups & Vans | Six-Tire Trucks | 3+ Axle SUTs | 3-4 Axle Combos | 5+ Axle Combos | |
| All Classes | 1.0000 | 1.0000 | 1.0000 | 1.0000 | 1.0000 | 1.0000 | 1.0000 |
| LDGV | 0.9991 | 0.9991 | |||||
| LDGT1 | 0.7303 | ||||||
| LDGT2 | 0.2571 | ||||||
| HDGV | 0.8002 | 0.3373 | 0.2470 | 0.0001 | |||
| MC | |||||||
| LDDV | 0.0009 | 0.0009 | |||||
| LDDT | 0.0126 | ||||||
| 2BHDDV | 0.1998 | ||||||
| LHDDV | 0.6627 | ||||||
| MHDDV | 0.7530 | ||||||
| HHDDV | 0.9999 | ||||||
| BUSES | |||||||
F.2.3 Future Trends in Emission Rates
In response to the progressive tightening of federal regulations on new motor vehicles' emission rates, the vehicles added to the U.S. fleet each year are significantly less polluting than those they replace.6 The downward trend in average emission rates resulting from such "turnover" of the vehicle fleet is reflected in the estimates of future emission rates for individual vehicle classes produced by the MOBILE6 and PART5 models.7 Thus the average emissions rates by vehicle class and speed for each pollutant and section type calculated by HERS will reflect this projected downward trend in future emission rates.
As a consequence, estimated air pollution costs under baseline and improved travel conditions on each sample section are predicted to decline over successive future funding periods. HERS' estimates of differences in air pollution costs between baseline and improved travel conditions on each section - which the model includes in its estimates of the benefits from potential improvements to the section - are also expected to narrow during each successive future funding period considered by HERS. Thus the effect of considering air pollution costs on the likelihood that HERS will select candidate improvements to a sample section also diminishes during each successive future funding period.
F.2.4 Final Emission Rates
This process produced a set of tables showing emissions of a single pollutant per vehicle-mile of travel at different average speeds by each of HERS' seven detailed vehicle classes, for one of its nine roadway section types. Table F-4 provides one example: it shows average carbon monoxide emissions (in grams per vehicle-mile traveled) at speeds from 5 to 50 mph for each of HERS' seven detailed vehicle classes operating on Rural Major Arterials, one of HERS' nine roadway section types, for the year 2000. In order to ensure that the projected decline in future emission rates is accurately reflected in the estimates of future air pollution damage costs - and in HERS' estimates of benefits or disbenefits from improvements proposed during future years - emission rates for each pollutant, vehicle class, and section type were also estimated for the year 2015. This represents approximately the outer time horizon recommended for use with the MOBILE6 and PART5 emissions models.
Average emissions rates for each pollutant and HERS vehicle class differ among the nine section types even at the same average speed, partly because the representation of the 16 different MOBILE6 vehicle classes and the 12 PART5 vehicle classes in each HERS vehicle class differs very slightly among section types. In addition, the typical driving cycles and resulting emissions rates that are associated with the same average speed differ among roadway types. For three of the six pollutants - carbon monoxide, volatile organic compounds, and nitrogen oxides - average emissions rates by individual HERS vehicle classes on each section type vary in response to changes in the average effective speed of travel. Thus the emission rates calculated by HERS for these three pollutants will differ between baseline conditions and those with each candidate improvement in place. In contrast, average emission rates for the three remaining pollutants - sulfur oxides, particulate matter, and road dust - do not vary significantly with travel speed, and will thus be identical under baseline and improved conditions within a funding period. Finally, average emission rates for all six pollutants generated by all vehicle classes on all section types will decline across the entire range of travel speeds during future years.
6. The effect on average emissions of adding new, cleaner vehicles to the fleet has been partly offset by the tendency for aging vehicles - most of which met less stringent emission standards when new - to be kept in service for longer periods and to be used more intensively than has historically been the case. Shifts toward heavier vehicles that are subject to less stringent emission standard, particularly the increasing substitution of light trucks (pickups, vans, and sport/utility vehicles) for automobiles as passenger vehicles, have also offset some of the effect of new vehicles' progressively lower emission rates. On balance, however, individual vehicle classes' and fleet-wide average emission rates for most pollutants have declined significantly in recent years, and are expected to decline significantly over the foreseeable future.
7. Both models also assume continued increases in the number of light-duty trucks used as passenger vehicles and in the average weight of heavy-duty trucks over the future, which slightly slow the decline in fleet-wide average emissions rates resulting from a progressively "cleaner" fleet.
| Speed (mph) | HERS Vehicle Class: | ||||||
|---|---|---|---|---|---|---|---|
| Small Autos | Medium/Large Autos | Pickups & Vans | Six-Tire Trucks | 3+ Axle SUTs | 3-4 Axle Combos | 5+ Axle Combos | |
| Source: estimated by Volpe Center using Table 2 and EPA MOBILE6 motor vehicle emission factor model. | |||||||
| 5 | 41.82 | 41.70 | 56.11 | 71.74 | 71.89 | 59.90 | 20.94 |
| 10 | 29.02 | 28.77 | 38.87 | 47.79 | 47.90 | 40.01 | 14.44 |
| 15 | 25.62 | 25.33 | 34.35 | 33.60 | 33.71 | 28.21 | 10.42 |
| 20 | 23.93 | 23.62 | 32.08 | 24.96 | 25.05 | 20.99 | 7.87 |
| 25 | 23.02 | 22.70 | 30.87 | 19.58 | 19.66 | 16.48 | 6.22 |
| 30 | 22.62 | 22.29 | 30.29 | 16.24 | 16.30 | 13.66 | 5.14 |
| 35 | 22.73 | 22.40 | 30.37 | 14.22 | 14.27 | 11.95 | 4.45 |
| 40 | 23.57 | 23.25 | 31.36 | 13.16 | 13.19 | 11.03 | 4.03 |
| 45 | 24.42 | 24.11 | 32.35 | 12.86 | 12.88 | 10.75 | 3.83 |
| 50 | 25.27 | 24.97 | 33.34 | 13.28 | 13.29 | 11.06 | 3.80 |
| 55 | 26.11 | 25.82 | 34.32 | 14.48 | 14.47 | 12.01 | 3.94 |
| 60 | 26.96 | 26.68 | 35.31 | 16.70 | 16.66 | 13.75 | 4.29 |
| 65 | 27.80 | 27.52 | 36.30 | 20.33 | 20.24 | 16.66 | 4.88 |
F.3 Air Pollution Damage Costs
F.3.1 Damage Costs for Individual Air Pollutants
The estimated costs of human health and property damage per ton of each pollutant that are employed in HERS were derived from a widely cited recent study.8 These values are derived by dividing the study's estimate of total annual costs from health and property damages caused by highway vehicles' contribution to atmospheric levels of each individual pollutant by the total number of tons of that pollutant emitted annually by highway vehicles. Thus they represent estimates of nationwide average damage costs per ton of each pollutant, given the typical atmospheric levels of those pollutants that prevailed at the time the study was conducted (1995). These values are assumed to represent acceptable estimates of the changes in total health and property damage costs that would result if emissions of each pollutant changed by one ton. HERS provides the option of using either the midpoint or the upper limit of the range for costs per ton of each pollutant implied by the study's reported range of estimates for total annual economic costs attributable to each pollutant. These dollar-denominated damage costs per ton of each pollutant are assumed to remain constant over all future funding periods considered by HERS.
8. McCubbin, D. and M. Delucchi. Health Effects of Motor Vehicle Air Pollution. Institute for Transportation Studies, University of California, Davis, 1996.
F.3.2 Adjustments to Per-Ton Damage Costs
The cost per ton estimates derived from this study represent average damage costs from exposure to prevailing air pollution levels that occurs at typical U.S. population and development densities. For pollutants that remain concentrated near their original sources, these average costs should be scaled up or down to reflect local variation in damage costs resulting from differences in population and property exposure to air pollution caused by higher or lower population and development density surrounding those sources. Unfortunately, however, usable information on the location of each sample sections is limited to whether it is located within an urbanized area or not; in the absence of more detailed data, HERS uses each sample section's urban or nonurban location to adjust the nationwide average costs per ton of each individual pollutant generated by vehicles traveling on it.
Specifically, HERS scales costs for the three pollutants that tend to remain localized (carbon monoxide, particulate matter, and road dust) downward from their national average values for sections located outside urbanized areas to reflect the lower density of rural populations located adjacent to highways and thus exposed to these pollutants. Damage costs per ton of these three pollutants emitted by vehicles using sample sections located in urban areas are assumed to equal their nationwide average values. In contrast, average damage costs for the three more widely dispersed pollutants - ozone, nitrogen oxides, and sulfur oxides - are scaled upward from their national averages for sample sections within urbanized areas in order to reflect the larger populations exposed to them. The scaling factors used in this process were developed by examining county-level population and population density data for the 100 largest U.S. metropolitan areas and comparing them to corresponding figures for all non-urbanized counties in the nation. Table F-5 summarizes the moderate and high estimates of per-ton damage costs for each pollutant, as well as the factors used by HERS to make these locational adjustments.
| Pollutant | Damage Costs ($/ton) | Adjustment Factor: | |
|---|---|---|---|
| Urban | Rural | ||
| Sources: McCubbin and DeLucchi, 1995, and Volpe Center analysis of county population density data from U.S. Census Bureau, 2000 Census of the United States. | |||
| Carbon Monoxide | $100 | 1.0 | 0.5 |
| Volatile Organic Compounds | $2,750 | 1.5 | 1.0 |
| Nitrogen Oxides | $3,625 | 1.5 | 1.0 |
| Sulfur Dioxide | $8,400 | 1.5 | 1.0 |
| Fine Particulate Matter (PM2.5) | $4,825 | 1.0 | 0.5 |
| Road Dust | $4,825 | 1.0 | 0.5 |
F.3.3 Air Pollution Costs per Vehicle-Mile
These damage costs per ton of each pollutant were multiplied by the previously-developed estimates of emissions per mile by vehicle class and speed for each HERS section type during the year 2000, with the per-ton damage cost for each pollutant adjusted appropriately to reflect its urban or rural location. The resulting values for each of the six pollutants were then summed to determine total air pollution damage costs per vehicle-mile of travel for each roadway type and location, vehicle class, and average speed at 5-mph intervals. Damage costs for 1-mph increments were interpolated from the surrounding values for 5-mph increments.
Values for the seven detailed vehicle classes used by HERS were then consolidated to the three aggregate vehicle classes for which the HPMS data records for individual sample sections provide estimated shares of travel (Four-Tire Vehicles, Single-Unit Trucks, and Combination Trucks), using the distributions of the seven detailed vehicle classes within each of these three broader classes on individual roadway types (reported previously in Table F-1); Table F-6 provides an example of the resulting values. Finally, this entire process was repeated for the year 2015, and annual rates of decline in emissions damage costs were estimated from their 2000 and 2015 values for each combination of vehicle class and roadway type. The annual percentage rates at which emission costs decline were assumed to be constant throughout this period (and beyond).
F.3.4 Assessing the Effect of Proposed Improvements on Air Pollution Costs
HERS calculates the economic costs of air pollution generated by annual travel on a sample section by multiplying its estimates of total annual vehicle-miles traveled by each vehicle class (Four-Tire Vehicles, Single-Unit Trucks, and Combination Trucks) by the value of air pollution damage costs per vehicle-mile for the appropriate vehicle class, roadway section type, average travel speed, and calendar year. Air pollution costs per vehicle-mile for the calendar year in which a proposed improvement is being evaluated are calculated by applying the average annual rate of decline over the appropriate number of years to the year-2000 cost estimates.
By repeating this procedure under the baseline and hypothetically improved travel conditions, HERS calculates the change in total air pollution costs generated by travel on the section that would result from implementing each proposed improvement. The change or difference in total air pollution costs between baseline and improved conditions increases or reduces net benefits from the improvement under consideration, depending on whether the changes in average effective speed and annual travel volume by each vehicle class resulting from that improvement cause air pollution costs to rise or decline. This process is repeated to evaluate the effect on net benefits from the candidate improvement from including air pollution costs during each future year making up the expected lifetime of that improvement. HERS then applies the usual process of discounting the stream of future net benefits from each candidate improvement - including its effect on air pollution costs - to its present value in order to evaluate the desirability of selecting that improvement during the current funding period.
F.3.5 Likely Effects of Including Air Pollution Costs
As indicated previously, proposed improvements to a sample section tend to increase air pollution costs by making travel on it less costly and thus raising the level of travel on the section. Thus if air pollutant emissions per vehicle-mile were unaffected by the changes in travel conditions that occur when sample sections are improved, air pollution costs would normally rise, thereby reducing the net benefits from typical improvements. At the same time, however, increases in the average effective speed of travel that result from an improvement can reduce average emissions per vehicle-mile for certain pollutants. By doing so, an improvement can thus reduce average air pollution costs per vehicle-mile traveled on the section, thereby offsetting some or all of the effect of higher travel volumes on total air pollution costs.
As Tables F-6 through F-14 suggests, per-mile air pollution costs on most facility types fall significantly as speeds increase up to about 40 mph, so benefits from improvements that increase speeds over this range are likely to be reduced only modestly - and may actually be increased in some cases - by including air pollution costs. Because per-mile emission rates and thus air pollution costs for most vehicle classes and roadway types begin to rise gradually above about 40 mph, however, large speed increases resulting from an improvement can accentuate the increase in air pollution costs caused by higher travel volumes.
Thus where travel speeds on sample sections under baseline or unimproved conditions are already above about 40 mph, the increase in air pollution costs resulting from the higher travel volumes produced by most improvements will be reinforced by an increase in per-mile air pollution costs. This same effect may also occur where baseline travel speeds are below the 45 mph threshold, but where candidate improvements to a sample section produce very large increases in travel speeds. In these cases, including air pollution costs may significantly reduce the net benefits from many potential improvements considered by HERS, making them less likely to be selected.
Air pollution damage costs per vehicle-mile differ considerably among the various section types considered by HERS across the entire range of travel speeds. Air pollution costs imposed by travel on facilities located in urban areas are significantly higher than those for identical facility types in rural areas because of the increased exposure to air pollution experienced by residents and properties surrounding sample sections located in urbanized areas. Average costs per vehicle-mile are also higher for facilities that carry larger shares of heavy vehicle travel (Interstate highways and other major arterials), since the per-mile rates at which trucks and other heavy vehicles emit some pollutants are much higher than those for light-duty vehicles. Thus considering air pollution costs is more likely to result in significant reductions in net benefits from candidate improvements to higher-order facilities (Interstate highways and other major arterials) and sample sections in urbanized locations.
On balance, the increase in air pollution costs from higher travel volumes seems likely to outweigh the effect of any decline in per-mile pollution costs for most proposed improvements. Thus considering air pollution costs will make most improvements slightly less likely to meet the benefit-cost criterion used by HERS to select improvements for adoption. Across the very large number of sample sections analyzed by HERS, the result seems likely to be a reduction in the number and value of improvement projects that are selected by HERS when the economic efficiency criterion is employed. Where projects are selected on a different basis, including air pollution costs is likely to reduce the net benefits generated by any selected set of improvements.
| Speed | Emission Damage Cost (2000 $ per vehicle-mile) | ||
|---|---|---|---|
| Four-Tire Vehicles | Single-Unit Trucks | Combination Trucks | |
| a. Source: estimated by Volpe Center using procedure described in text. | |||
| b. Projected annual rate of decline after year 2000. | |||
| 5 | $0.03283 | $0.05347 | $0.14932 |
| 6 | $0.02902 | $0.04925 | $0.14350 |
| 7 | $0.02630 | $0.04623 | $0.13935 |
| 8 | $0.02426 | $0.04397 | $0.13623 |
| 9 | $0.02267 | $0.04221 | $0.13380 |
| 10 | $0.02140 | $0.04081 | $0.13186 |
| 11 | $0.02031 | $0.03930 | $0.12864 |
| 12 | $0.01940 | $0.03805 | $0.12595 |
| 13 | $0.01863 | $0.03699 | $0.12368 |
| 14 | $0.01797 | $0.03608 | $0.12173 |
| 15 | $0.01740 | $0.03529 | $0.12004 |
| 16 | $0.01708 | $0.03448 | $0.11805 |
| 17 | $0.01680 | $0.03376 | $0.11630 |
| 18 | $0.01655 | $0.03312 | $0.11474 |
| 19 | $0.01633 | $0.03255 | $0.11334 |
| 20 | $0.01613 | $0.03204 | $0.11209 |
| 21 | $0.01576 | $0.03162 | $0.11088 |
| 22 | $0.01543 | $0.03125 | $0.10978 |
| 23 | $0.01512 | $0.03091 | $0.10877 |
| 24 | $0.01484 | $0.03060 | $0.10785 |
| 25 | $0.01459 | $0.03031 | $0.10701 |
| 26 | $0.01477 | $0.03010 | $0.10636 |
| 27 | $0.01493 | $0.02991 | $0.10575 |
| 28 | $0.01509 | $0.02973 | $0.10520 |
| 29 | $0.01523 | $0.02956 | $0.10468 |
| 30 | $0.01537 | $0.02941 | $0.10419 |
| 31 | $0.01530 | $0.02933 | $0.10400 |
| 32 | $0.01523 | $0.02926 | $0.10381 |
| 33 | $0.01517 | $0.02919 | $0.10364 |
| 34 | $0.01511 | $0.02913 | $0.10348 |
| 35 | $0.01506 | $0.02907 | $0.10333 |
| 36 | $0.01506 | $0.02909 | $0.10355 |
| 37 | $0.01506 | $0.02910 | $0.10376 |
| 38 | $0.01505 | $0.02912 | $0.10395 |
| 39 | $0.01505 | $0.02914 | $0.10414 |
| 40 | $0.01505 | $0.02915 | $0.10432 |
| 41 | $0.01506 | $0.02925 | $0.10497 |
| 42 | $0.01506 | $0.02934 | $0.10559 |
| 43 | $0.01507 | $0.02943 | $0.10618 |
| 44 | $0.01507 | $0.02951 | $0.10674 |
| 45 | $0.01508 | $0.02959 | $0.10727 |
| 46 | $0.01509 | $0.02977 | $0.10842 |
| 47 | $0.01510 | $0.02994 | $0.10951 |
| 48 | $0.01511 | $0.03010 | $0.11056 |
| 49 | $0.01511 | $0.03026 | $0.11157 |
| 50 | $0.01512 | $0.03041 | $0.11254 |
| 51 | $0.01514 | $0.03068 | $0.11430 |
| 52 | $0.01515 | $0.03093 | $0.11600 |
| 53 | $0.01516 | $0.03117 | $0.11763 |
| 54 | $0.01518 | $0.03140 | $0.11920 |
| 55 | $0.01519 | $0.03163 | $0.12072 |
| 56 | $0.01521 | $0.03200 | $0.12332 |
| 57 | $0.01523 | $0.03236 | $0.12584 |
| 58 | $0.01525 | $0.03271 | $0.12826 |
| 59 | $0.01527 | $0.03304 | $0.13061 |
| 60 | $0.01529 | $0.03336 | $0.13287 |
| 61 | $0.01531 | $0.03389 | $0.13667 |
| 62 | $0.01533 | $0.03439 | $0.14034 |
| 63 | $0.01536 | $0.03488 | $0.14390 |
| 64 | $0.01538 | $0.03535 | $0.14734 |
| 65 | $0.01540 | $0.03581 | $0.15068 |
| 66 | $0.01542 | $0.03627 | $0.15410 |
| 67 | $0.01544 | $0.03675 | $0.15759 |
| 68 | $0.01546 | $0.03722 | $0.16116 |
| 69 | $0.01548 | $0.03771 | $0.16481 |
| 70 | $0.01550 | $0.03820 | $0.16855 |
| rb | 6.27% | 7.79% | 12.17% |
| Average Speed (mph) | Emission Damage Cost (2000 $ per vehicle-mile) | ||
|---|---|---|---|
| Four-Tire Vehicles | Single-Unit Trucks | Combination Trucks | |
| a. Source: estimated by Volpe Center using procedure described in text. | |||
| b. Projected annual rate of decline after year 2000. | |||
| 5 | $0.03584 | $0.05605 | $0.12750 |
| 6 | $0.03169 | $0.05145 | $0.12117 |
| 7 | $0.02872 | $0.04816 | $0.11665 |
| 8 | $0.02649 | $0.04570 | $0.11326 |
| 9 | $0.02476 | $0.04378 | $0.11062 |
| 10 | $0.02338 | $0.04224 | $0.10851 |
| 11 | $0.02228 | $0.04059 | $0.10504 |
| 12 | $0.02136 | $0.03921 | $0.10214 |
| 13 | $0.02059 | $0.03804 | $0.09969 |
| 14 | $0.01993 | $0.03704 | $0.09759 |
| 15 | $0.01935 | $0.03617 | $0.09577 |
| 16 | $0.01880 | $0.03527 | $0.09362 |
| 17 | $0.01831 | $0.03448 | $0.09172 |
| 18 | $0.01787 | $0.03377 | $0.09004 |
| 19 | $0.01748 | $0.03314 | $0.08853 |
| 20 | $0.01713 | $0.03257 | $0.08717 |
| 21 | $0.01687 | $0.03212 | $0.08587 |
| 22 | $0.01663 | $0.03170 | $0.08468 |
| 23 | $0.01641 | $0.03132 | $0.08360 |
| 24 | $0.01621 | $0.03098 | $0.08260 |
| 25 | $0.01602 | $0.03066 | $0.08169 |
| 26 | $0.01586 | $0.03042 | $0.08099 |
| 27 | $0.01571 | $0.03021 | $0.08034 |
| 28 | $0.01558 | $0.03000 | $0.07974 |
| 29 | $0.01545 | $0.02982 | $0.07917 |
| 30 | $0.01533 | $0.02964 | $0.07865 |
| 31 | $0.01523 | $0.02956 | $0.07844 |
| 32 | $0.01514 | $0.02948 | $0.07824 |
| 33 | $0.01506 | $0.02941 | $0.07805 |
| 34 | $0.01498 | $0.02934 | $0.07788 |
| 35 | $0.01490 | $0.02927 | $0.07771 |
| 36 | $0.01490 | $0.02929 | $0.07863 |
| 37 | $0.01490 | $0.02931 | $0.07949 |
| 38 | $0.01489 | $0.02933 | $0.08030 |
| 39 | $0.01489 | $0.02934 | $0.08108 |
| 40 | $0.01489 | $0.02936 | $0.08181 |
| 41 | $0.01489 | $0.02947 | $0.08185 |
| 42 | $0.01490 | $0.02957 | $0.08188 |
| 43 | $0.01491 | $0.02967 | $0.08191 |
| 44 | $0.01492 | $0.02977 | $0.08194 |
| 45 | $0.01492 | $0.02986 | $0.08196 |
| 46 | $0.01493 | $0.03006 | $0.08319 |
| 47 | $0.01494 | $0.03025 | $0.08437 |
| 48 | $0.01495 | $0.03043 | $0.08550 |
| 49 | $0.01496 | $0.03060 | $0.08658 |
| 50 | $0.01497 | $0.03077 | $0.08762 |
| 51 | $0.01499 | $0.03107 | $0.08952 |
| 52 | $0.01500 | $0.03136 | $0.09135 |
| 53 | $0.01502 | $0.03163 | $0.09311 |
| 54 | $0.01503 | $0.03190 | $0.09480 |
| 55 | $0.01505 | $0.03215 | $0.09643 |
| 56 | $0.01507 | $0.03258 | $0.09924 |
| 57 | $0.01509 | $0.03298 | $0.10194 |
| 58 | $0.01511 | $0.03338 | $0.10456 |
| 59 | $0.01513 | $0.03376 | $0.10708 |
| 60 | $0.01515 | $0.03413 | $0.10952 |
| 61 | $0.01516 | $0.03473 | $0.11360 |
| 62 | $0.01517 | $0.03530 | $0.11755 |
| 63 | $0.01518 | $0.03586 | $0.12138 |
| 64 | $0.01519 | $0.03640 | $0.12508 |
| 65 | $0.01520 | $0.03693 | $0.12868 |
| 66 | $0.01520 | $0.03746 | $0.13237 |
| 67 | $0.01521 | $0.03800 | $0.13617 |
| 68 | $0.01522 | $0.03855 | $0.14008 |
| 69 | $0.01523 | $0.03911 | $0.14411 |
| 70 | $0.01524 | $0.03967 | $0.14825 |
| rb | 6.06% | 7.79% | 11.30% |
| Speed (mph) | Emission Damage Cost (2000 $ per vehicle-mile) | ||
|---|---|---|---|
| Four-Tire Vehicles | Single-Unit Trucks | Combination Trucks | |
| a. Source: estimated by Volpe Center using procedure described in text. | |||
| b. Projected annual rate of decline after year 2000. | |||
| 5 | $0.03586 | $0.05609 | $0.12643 |
| 6 | $0.03170 | $0.05149 | $0.12011 |
| 7 | $0.02873 | $0.04820 | $0.11560 |
| 8 | $0.02651 | $0.04573 | $0.11221 |
| 9 | $0.02477 | $0.04381 | $0.10958 |
| 10 | $0.02339 | $0.04228 | $0.10747 |
| 11 | $0.02229 | $0.04062 | $0.10402 |
| 12 | $0.02138 | $0.03924 | $0.10114 |
| 13 | $0.02060 | $0.03807 | $0.09871 |
| 14 | $0.01994 | $0.03707 | $0.09662 |
| 15 | $0.01936 | $0.03620 | $0.09482 |
| 16 | $0.01881 | $0.03530 | $0.09268 |
| 17 | $0.01832 | $0.03450 | $0.09080 |
| 18 | $0.01788 | $0.03380 | $0.08913 |
| 19 | $0.01749 | $0.03317 | $0.08763 |
| 20 | $0.01714 | $0.03260 | $0.08628 |
| 21 | $0.01688 | $0.03214 | $0.08499 |
| 22 | $0.01664 | $0.03172 | $0.08381 |
| 23 | $0.01642 | $0.03134 | $0.08273 |
| 24 | $0.01622 | $0.03100 | $0.08175 |
| 25 | $0.01603 | $0.03068 | $0.08084 |
| 26 | $0.01587 | $0.03044 | $0.08014 |
| 27 | $0.01573 | $0.03022 | $0.07950 |
| 28 | $0.01559 | $0.03002 | $0.07890 |
| 29 | $0.01546 | $0.02984 | $0.07834 |
| 30 | $0.01534 | $0.02966 | $0.07782 |
| 31 | $0.01524 | $0.02958 | $0.07761 |
| 32 | $0.01515 | $0.02950 | $0.07741 |
| 33 | $0.01507 | $0.02942 | $0.07723 |
| 34 | $0.01499 | $0.02936 | $0.07705 |
| 35 | $0.01491 | $0.02929 | $0.07689 |
| 36 | $0.01491 | $0.02931 | $0.07778 |
| 37 | $0.01491 | $0.02933 | $0.07862 |
| 38 | $0.01490 | $0.02934 | $0.07942 |
| 39 | $0.01490 | $0.02936 | $0.08017 |
| 40 | $0.01490 | $0.02937 | $0.08089 |
| 41 | $0.01490 | $0.02948 | $0.08094 |
| 42 | $0.01491 | $0.02959 | $0.08097 |
| 43 | $0.01492 | $0.02969 | $0.08101 |
| 44 | $0.01493 | $0.02979 | $0.08105 |
| 45 | $0.01493 | $0.02988 | $0.08108 |
| 46 | $0.01494 | $0.03008 | $0.08230 |
| 47 | $0.01495 | $0.03027 | $0.08346 |
| 48 | $0.01496 | $0.03045 | $0.08458 |
| 49 | $0.01497 | $0.03063 | $0.08565 |
| 50 | $0.01498 | $0.03079 | $0.08667 |
| 51 | $0.01500 | $0.03109 | $0.08855 |
| 52 | $0.01501 | $0.03138 | $0.09036 |
| 53 | $0.01503 | $0.03165 | $0.09210 |
| 54 | $0.01504 | $0.03192 | $0.09377 |
| 55 | $0.01506 | $0.03218 | $0.09538 |
| 56 | $0.01508 | $0.03260 | $0.09815 |
| 57 | $0.01510 | $0.03301 | $0.10083 |
| 58 | $0.01512 | $0.03341 | $0.10341 |
| 59 | $0.01514 | $0.03379 | $0.10590 |
| 60 | $0.01516 | $0.03416 | $0.10831 |
| 61 | $0.01517 | $0.03476 | $0.11235 |
| 62 | $0.01518 | $0.03534 | $0.11625 |
| 63 | $0.01519 | $0.03590 | $0.12003 |
| 64 | $0.01520 | $0.03644 | $0.12369 |
| 65 | $0.01521 | $0.03697 | $0.12724 |
| 66 | $0.01521 | $0.03750 | $0.13090 |
| 67 | $0.01522 | $0.03805 | $0.13465 |
| 68 | $0.01523 | $0.03860 | $0.13852 |
| 69 | $0.01524 | $0.03916 | $0.14249 |
| 70 | $0.01525 | $0.03973 | $0.14658 |
| rb | 6.06% | 7.79% | 11.25% |
| Speed (mph) | Emission Damage Cost (2000 $ per vehicle-mile) | ||
|---|---|---|---|
| Four-Tire Vehicles | Single-Unit Trucks | Combination Trucks | |
| a. Source: estimated by Volpe Center using procedure described in text. | |||
| b. Projected annual rate of decline after year 2000. | |||
| 5 | $0.03599 | $0.05627 | $0.12618 |
| 6 | $0.03182 | $0.05166 | $0.11986 |
| 7 | $0.02885 | $0.04837 | $0.11535 |
| 8 | $0.02662 | $0.04590 | $0.11197 |
| 9 | $0.02488 | $0.04398 | $0.10934 |
| 10 | $0.02349 | $0.04244 | $0.10723 |
| 11 | $0.02239 | $0.04077 | $0.10379 |
| 12 | $0.02147 | $0.03938 | $0.10092 |
| 13 | $0.02070 | $0.03821 | $0.09849 |
| 14 | $0.02003 | $0.03720 | $0.09640 |
| 15 | $0.01946 | $0.03633 | $0.09460 |
| 16 | $0.01890 | $0.03542 | $0.09247 |
| 17 | $0.01841 | $0.03462 | $0.09059 |
| 18 | $0.01797 | $0.03391 | $0.08892 |
| 19 | $0.01758 | $0.03328 | $0.08742 |
| 20 | $0.01723 | $0.03271 | $0.08608 |
| 21 | $0.01697 | $0.03224 | $0.08478 |
| 22 | $0.01673 | $0.03182 | $0.08361 |
| 23 | $0.01651 | $0.03144 | $0.08253 |
| 24 | $0.01630 | $0.03109 | $0.08155 |
| 25 | $0.01612 | $0.03077 | $0.08064 |
| 26 | $0.01596 | $0.03053 | $0.07995 |
| 27 | $0.01581 | $0.03031 | $0.07930 |
| 28 | $0.01567 | $0.03011 | $0.07871 |
| 29 | $0.01554 | $0.02992 | $0.07815 |
| 30 | $0.01542 | $0.02974 | $0.07763 |
| 31 | $0.01533 | $0.02966 | $0.07742 |
| 32 | $0.01524 | $0.02958 | $0.07722 |
| 33 | $0.01515 | $0.02950 | $0.07704 |
| 34 | $0.01507 | $0.02943 | $0.07686 |
| 35 | $0.01500 | $0.02937 | $0.07670 |
| 36 | $0.01499 | $0.02938 | $0.07759 |
| 37 | $0.01499 | $0.02940 | $0.07842 |
| 38 | $0.01499 | $0.02942 | $0.07922 |
| 39 | $0.01498 | $0.02943 | $0.07997 |
| 40 | $0.01498 | $0.02945 | $0.08068 |
| 41 | $0.01499 | $0.02956 | $0.08073 |
| 42 | $0.01500 | $0.02967 | $0.08077 |
| 43 | $0.01501 | $0.02977 | $0.08081 |
| 44 | $0.01501 | $0.02987 | $0.08085 |
| 45 | $0.01502 | $0.02996 | $0.08088 |
| 46 | $0.01503 | $0.03016 | $0.08209 |
| 47 | $0.01504 | $0.03036 | $0.08325 |
| 48 | $0.01505 | $0.03054 | $0.08437 |
| 49 | $0.01506 | $0.03072 | $0.08543 |
| 50 | $0.01507 | $0.03089 | $0.08646 |
| 51 | $0.01509 | $0.03119 | $0.08833 |
| 52 | $0.01510 | $0.03148 | $0.09013 |
| 53 | $0.01512 | $0.03176 | $0.09186 |
| 54 | $0.01513 | $0.03203 | $0.09353 |
| 55 | $0.01515 | $0.03229 | $0.09514 |
| 56 | $0.01517 | $0.03273 | $0.09790 |
| 57 | $0.01519 | $0.03315 | $0.10057 |
| 58 | $0.01521 | $0.03355 | $0.10315 |
| 59 | $0.01523 | $0.03394 | $0.10563 |
| 60 | $0.01525 | $0.03432 | $0.10804 |
| 61 | $0.01526 | $0.03492 | $0.11206 |
| 62 | $0.01527 | $0.03551 | $0.11595 |
| 63 | $0.01527 | $0.03609 | $0.11972 |
| 64 | $0.01528 | $0.03664 | $0.12338 |
| 65 | $0.01529 | $0.03718 | $0.12692 |
| 66 | $0.01530 | $0.03772 | $0.13056 |
| 67 | $0.01530 | $0.03827 | $0.13430 |
| 68 | $0.01531 | $0.03884 | $0.13816 |
| 69 | $0.01532 | $0.03941 | $0.14212 |
| 70 | $0.01533 | $0.03999 | $0.14620 |
| rb | 6.05% | 7.80% | 11.24% |
| Speed (mph) | Emission Damage Cost (2000 $ per vehicle-mile) | ||
|---|---|---|---|
| Four-Tire Vehicles | Single-Unit Trucks | Combination Trucks | |
| a. Source: estimated by Volpe Center using procedure described in text. | |||
| b. Projected annual rate of decline after year 2000. | |||
| 5 | $0.02562 | $0.04511 | $0.14771 |
| 6 | $0.02256 | $0.04200 | $0.14188 |
| 7 | $0.02038 | $0.03978 | $0.13772 |
| 8 | $0.01875 | $0.03811 | $0.13460 |
| 9 | $0.01747 | $0.03681 | $0.13217 |
| 10 | $0.01646 | $0.03578 | $0.13023 |
| 11 | $0.01566 | $0.03454 | $0.12709 |
| 12 | $0.01499 | $0.03351 | $0.12447 |
| 13 | $0.01443 | $0.03264 | $0.12225 |
| 14 | $0.01395 | $0.03189 | $0.12035 |
| 15 | $0.01353 | $0.03124 | $0.11871 |
| 16 | $0.01338 | $0.03058 | $0.11674 |
| 17 | $0.01324 | $0.03000 | $0.11500 |
| 18 | $0.01312 | $0.02949 | $0.11345 |
| 19 | $0.01301 | $0.02902 | $0.11207 |
| 20 | $0.01291 | $0.02861 | $0.11083 |
| 21 | $0.01283 | $0.02826 | $0.10963 |
| 22 | $0.01275 | $0.02794 | $0.10854 |
| 23 | $0.01268 | $0.02765 | $0.10754 |
| 24 | $0.01262 | $0.02739 | $0.10663 |
| 25 | $0.01256 | $0.02714 | $0.10579 |
| 26 | $0.01250 | $0.02697 | $0.10515 |
| 27 | $0.01245 | $0.02682 | $0.10455 |
| 28 | $0.01240 | $0.02667 | $0.10400 |
| 29 | $0.01235 | $0.02654 | $0.10349 |
| 30 | $0.01231 | $0.02641 | $0.10301 |
| 31 | $0.01226 | $0.02636 | $0.10281 |
| 32 | $0.01221 | $0.02632 | $0.10263 |
| 33 | $0.01217 | $0.02627 | $0.10246 |
| 34 | $0.01213 | $0.02623 | $0.10230 |
| 35 | $0.01209 | $0.02619 | $0.10215 |
| 36 | $0.01209 | $0.02623 | $0.10237 |
| 37 | $0.01209 | $0.02627 | $0.10258 |
| 38 | $0.01209 | $0.02630 | $0.10277 |
| 39 | $0.01209 | $0.02634 | $0.10296 |
| 40 | $0.01209 | $0.02637 | $0.10314 |
| 41 | $0.01211 | $0.02648 | $0.10378 |
| 42 | $0.01212 | $0.02659 | $0.10439 |
| 43 | $0.01214 | $0.02670 | $0.10498 |
| 44 | $0.01215 | $0.02680 | $0.10553 |
| 45 | $0.01216 | $0.02689 | $0.10607 |
| 46 | $0.01217 | $0.02708 | $0.10720 |
| 47 | $0.01219 | $0.02726 | $0.10829 |
| 48 | $0.01220 | $0.02743 | $0.10933 |
| 49 | $0.01221 | $0.02759 | $0.11032 |
| 50 | $0.01222 | $0.02775 | $0.11128 |
| 51 | $0.01224 | $0.02802 | $0.11303 |
| 52 | $0.01225 | $0.02828 | $0.11471 |
| 53 | $0.01227 | $0.02853 | $0.11633 |
| 54 | $0.01228 | $0.02877 | $0.11789 |
| 55 | $0.01229 | $0.02901 | $0.11940 |
| 56 | $0.01231 | $0.02938 | $0.12198 |
| 57 | $0.01233 | $0.02975 | $0.12447 |
| 58 | $0.01235 | $0.03010 | $0.12687 |
| 59 | $0.01237 | $0.03044 | $0.12919 |
| 60 | $0.01239 | $0.03077 | $0.13144 |
| 61 | $0.01241 | $0.03129 | $0.13520 |
| 62 | $0.01243 | $0.03180 | $0.13883 |
| 63 | $0.01245 | $0.03229 | $0.14236 |
| 64 | $0.01247 | $0.03276 | $0.14577 |
| 65 | $0.01249 | $0.03322 | $0.14908 |
| 66 | $0.01251 | $0.03369 | $0.15246 |
| 67 | $0.01253 | $0.03416 | $0.15592 |
| 68 | $0.01255 | $0.03465 | $0.15945 |
| 69 | $0.01256 | $0.03514 | $0.16307 |
| 70 | $0.01258 | $0.03563 | $0.16677 |
| rb | 6.77% | 8.07% | 12.15% |
| Speed (mph) | Emission Damage Cost (2000 $ per vehicle-mile) | ||
|---|---|---|---|
| Four-Tire Vehicles | Single-Unit Trucks | Combination Trucks | |
| a. Source: estimated by Volpe Center using procedure described in text. | |||
| b. Projected annual rate of decline after year 2000. | |||
| 5 | $0.02550 | $0.04503 | $0.14537 |
| 6 | $0.02246 | $0.04192 | $0.13959 |
| 7 | $0.02028 | $0.03970 | $0.13546 |
| 8 | $0.01865 | $0.03804 | $0.13236 |
| 9 | $0.01739 | $0.03674 | $0.12995 |
| 10 | $0.01637 | $0.03571 | $0.12802 |
| 11 | $0.01558 | $0.03447 | $0.12491 |
| 12 | $0.01492 | $0.03344 | $0.12231 |
| 13 | $0.01436 | $0.03258 | $0.12011 |
| 14 | $0.01388 | $0.03183 | $0.11823 |
| 15 | $0.01346 | $0.03118 | $0.11660 |
| 16 | $0.01331 | $0.03053 | $0.11465 |
| 17 | $0.01317 | $0.02995 | $0.11293 |
| 18 | $0.01305 | $0.02943 | $0.11140 |
| 19 | $0.01294 | $0.02897 | $0.11003 |
| 20 | $0.01284 | $0.02856 | $0.10880 |
| 21 | $0.01276 | $0.02821 | $0.10762 |
| 22 | $0.01268 | $0.02790 | $0.10654 |
| 23 | $0.01261 | $0.02761 | $0.10556 |
| 24 | $0.01255 | $0.02734 | $0.10465 |
| 25 | $0.01249 | $0.02710 | $0.10383 |
| 26 | $0.01244 | $0.02693 | $0.10319 |
| 27 | $0.01238 | $0.02678 | $0.10260 |
| 28 | $0.01233 | $0.02663 | $0.10205 |
| 29 | $0.01229 | $0.02650 | $0.10154 |
| 30 | $0.01224 | $0.02637 | $0.10107 |
| 31 | $0.01219 | $0.02632 | $0.10088 |
| 32 | $0.01215 | $0.02628 | $0.10070 |
| 33 | $0.01210 | $0.02624 | $0.10053 |
| 34 | $0.01206 | $0.02619 | $0.10037 |
| 35 | $0.01202 | $0.02616 | $0.10022 |
| 36 | $0.01202 | $0.02620 | $0.10044 |
| 37 | $0.01202 | $0.02623 | $0.10064 |
| 38 | $0.01202 | $0.02627 | $0.10083 |
| 39 | $0.01202 | $0.02630 | $0.10102 |
| 40 | $0.01203 | $0.02633 | $0.10119 |
| 41 | $0.01204 | $0.02645 | $0.10182 |
| 42 | $0.01205 | $0.02655 | $0.10242 |
| 43 | $0.01207 | $0.02666 | $0.10300 |
| 44 | $0.01208 | $0.02676 | $0.10355 |
| 45 | $0.01209 | $0.02685 | $0.10407 |
| 46 | $0.01211 | $0.02704 | $0.10519 |
| 47 | $0.01212 | $0.02722 | $0.10626 |
| 48 | $0.01213 | $0.02739 | $0.10728 |
| 49 | $0.01214 | $0.02755 | $0.10826 |
| 50 | $0.01215 | $0.02771 | $0.10920 |
| 51 | $0.01217 | $0.02798 | $0.11093 |
| 52 | $0.01218 | $0.02824 | $0.11258 |
| 53 | $0.01220 | $0.02849 | $0.11417 |
| 54 | $0.01221 | $0.02873 | $0.11571 |
| 55 | $0.01223 | $0.02896 | $0.11719 |
| 56 | $0.01225 | $0.02933 | $0.11973 |
| 57 | $0.01227 | $0.02969 | $0.12218 |
| 58 | $0.01229 | $0.03004 | $0.12454 |
| 59 | $0.01230 | $0.03038 | $0.12683 |
| 60 | $0.01232 | $0.03071 | $0.12904 |
| 61 | $0.01234 | $0.03123 | $0.13273 |
| 62 | $0.01236 | $0.03173 | $0.13631 |
| 63 | $0.01238 | $0.03222 | $0.13978 |
| 64 | $0.01240 | $0.03269 | $0.14313 |
| 65 | $0.01242 | $0.03314 | $0.14639 |
| 66 | $0.01244 | $0.03361 | $0.14972 |
| 67 | $0.01246 | $0.03408 | $0.15312 |
| 68 | $0.01248 | $0.03456 | $0.15660 |
| 69 | $0.01250 | $0.03504 | $0.16016 |
| 70 | $0.01251 | $0.03553 | $0.16380 |
| rb | 6.77% | 8.07% | 12.15% |
| Speed (mph) | Emission Damage Cost (2000 $ per vehicle-mile) | ||
|---|---|---|---|
| Four-Tire Vehicles | Single-Unit Trucks | Combination Trucks | |
| a. Source: estimated by Volpe Center using procedure described in text. | |||
| b. Projected annual rate of decline after year 2000. | |||
| 5 | $0.02669 | $0.04726 | $0.12349 |
| 6 | $0.02369 | $0.04387 | $0.11733 |
| 7 | $0.02155 | $0.04145 | $0.11293 |
| 8 | $0.01994 | $0.03964 | $0.10963 |
| 9 | $0.01869 | $0.03823 | $0.10706 |
| 10 | $0.01769 | $0.03710 | $0.10501 |
| 11 | $0.01700 | $0.03575 | $0.10161 |
| 12 | $0.01643 | $0.03462 | $0.09877 |
| 13 | $0.01594 | $0.03367 | $0.09637 |
| 14 | $0.01553 | $0.03286 | $0.09432 |
| 15 | $0.01517 | $0.03215 | $0.09254 |
| 16 | $0.01479 | $0.03143 | $0.09045 |
| 17 | $0.01446 | $0.03080 | $0.08860 |
| 18 | $0.01416 | $0.03024 | $0.08697 |
| 19 | $0.01390 | $0.02973 | $0.08550 |
| 20 | $0.01366 | $0.02928 | $0.08418 |
| 21 | $0.01345 | $0.02890 | $0.08291 |
| 22 | $0.01327 | $0.02855 | $0.08176 |
| 23 | $0.01310 | $0.02824 | $0.08071 |
| 24 | $0.01294 | $0.02795 | $0.07974 |
| 25 | $0.01280 | $0.02768 | $0.07885 |
| 26 | $0.01267 | $0.02749 | $0.07817 |
| 27 | $0.01256 | $0.02732 | $0.07754 |
| 28 | $0.01245 | $0.02716 | $0.07695 |
| 29 | $0.01236 | $0.02702 | $0.07641 |
| 30 | $0.01226 | $0.02688 | $0.07590 |
| 31 | $0.01219 | $0.02682 | $0.07569 |
| 32 | $0.01212 | $0.02677 | $0.07550 |
| 33 | $0.01206 | $0.02673 | $0.07532 |
| 34 | $0.01199 | $0.02668 | $0.07515 |
| 35 | $0.01194 | $0.02664 | $0.07499 |
| 36 | $0.01194 | $0.02668 | $0.07522 |
| 37 | $0.01194 | $0.02672 | $0.07543 |
| 38 | $0.01195 | $0.02675 | $0.07564 |
| 39 | $0.01195 | $0.02678 | $0.07583 |
| 40 | $0.01195 | $0.02681 | $0.07601 |
| 41 | $0.01197 | $0.02694 | $0.07669 |
| 42 | $0.01198 | $0.02706 | $0.07733 |
| 43 | $0.01199 | $0.02718 | $0.07794 |
| 44 | $0.01200 | $0.02729 | $0.07853 |
| 45 | $0.01201 | $0.02740 | $0.07908 |
| 46 | $0.01202 | $0.02760 | $0.08027 |
| 47 | $0.01204 | $0.02780 | $0.08141 |
| 48 | $0.01205 | $0.02799 | $0.08249 |
| 49 | $0.01206 | $0.02817 | $0.08354 |
| 50 | $0.01207 | $0.02834 | $0.08454 |
| 51 | $0.01209 | $0.02864 | $0.08637 |
| 52 | $0.01211 | $0.02892 | $0.08813 |
| 53 | $0.01213 | $0.02920 | $0.08983 |
| 54 | $0.01214 | $0.02946 | $0.09146 |
| 55 | $0.01216 | $0.02972 | $0.09304 |
| 56 | $0.01218 | $0.03013 | $0.09574 |
| 57 | $0.01220 | $0.03053 | $0.09835 |
| 58 | $0.01222 | $0.03091 | $0.10086 |
| 59 | $0.01224 | $0.03128 | $0.10329 |
| 60 | $0.01226 | $0.03164 | $0.10565 |
| 61 | $0.01228 | $0.03222 | $0.10958 |
| 62 | $0.01231 | $0.03277 | $0.11339 |
| 63 | $0.01233 | $0.03331 | $0.11707 |
| 64 | $0.01235 | $0.03383 | $0.12064 |
| 65 | $0.01237 | $0.03434 | $0.12410 |
| 66 | $0.01239 | $0.03485 | $0.12766 |
| 67 | $0.01241 | $0.03537 | $0.13133 |
| 68 | $0.01243 | $0.03590 | $0.13509 |
| 69 | $0.01246 | $0.03644 | $0.13897 |
| 70 | $0.01248 | $0.03699 | $0.14296 |
| rb | 6.72% | 8.16% | 11.19% |
| Speed (mph) | Emission Damage Cost (2000 $ per vehicle-mile) | ||
|---|---|---|---|
| Four-Tire Vehicles | Single-Unit Trucks | Combination Trucks | |
| a. Source: estimated by Volpe Center using procedure described in text. | |||
| b. Projected annual rate of decline after year 2000. | |||
| 5 | $0.02662 | $0.04827 | $0.11858 |
| 6 | $0.02363 | $0.04482 | $0.11254 |
| 7 | $0.02150 | $0.04236 | $0.10823 |
| 8 | $0.01990 | $0.04052 | $0.10500 |
| 9 | $0.01865 | $0.03908 | $0.10249 |
| 10 | $0.01765 | $0.03793 | $0.10047 |
| 11 | $0.01696 | $0.03654 | $0.09717 |
| 12 | $0.01639 | $0.03538 | $0.09442 |
| 13 | $0.01590 | $0.03440 | $0.09210 |
| 14 | $0.01548 | $0.03356 | $0.09010 |
| 15 | $0.01512 | $0.03283 | $0.08837 |
| 16 | $0.01475 | $0.03209 | $0.08635 |
| 17 | $0.01441 | $0.03143 | $0.08457 |
| 18 | $0.01412 | $0.03084 | $0.08299 |
| 19 | $0.01386 | $0.03032 | $0.08157 |
| 20 | $0.01362 | $0.02984 | $0.08030 |
| 21 | $0.01341 | $0.02944 | $0.07907 |
| 22 | $0.01323 | $0.02908 | $0.07796 |
| 23 | $0.01306 | $0.02875 | $0.07694 |
| 24 | $0.01290 | $0.02845 | $0.07601 |
| 25 | $0.01276 | $0.02817 | $0.07516 |
| 26 | $0.01264 | $0.02797 | $0.07450 |
| 27 | $0.01252 | $0.02779 | $0.07389 |
| 28 | $0.01242 | $0.02762 | $0.07333 |
| 29 | $0.01232 | $0.02746 | $0.07280 |
| 30 | $0.01223 | $0.02731 | $0.07231 |
| 31 | $0.01215 | $0.02725 | $0.07211 |
| 32 | $0.01208 | $0.02720 | $0.07192 |
| 33 | $0.01202 | $0.02714 | $0.07175 |
| 34 | $0.01196 | $0.02710 | $0.07158 |
| 35 | $0.01190 | $0.02705 | $0.07142 |
| 36 | $0.01190 | $0.02709 | $0.07164 |
| 37 | $0.01191 | $0.02712 | $0.07184 |
| 38 | $0.01191 | $0.02715 | $0.07203 |
| 39 | $0.01191 | $0.02719 | $0.07221 |
| 40 | $0.01192 | $0.02722 | $0.07239 |
| 41 | $0.01193 | $0.02735 | $0.07303 |
| 42 | $0.01194 | $0.02748 | $0.07363 |
| 43 | $0.01195 | $0.02760 | $0.07421 |
| 44 | $0.01196 | $0.02772 | $0.07477 |
| 45 | $0.01197 | $0.02783 | $0.07530 |
| 46 | $0.01199 | $0.02805 | $0.07642 |
| 47 | $0.01200 | $0.02826 | $0.07750 |
| 48 | $0.01201 | $0.02846 | $0.07853 |
| 49 | $0.01202 | $0.02865 | $0.07953 |
| 50 | $0.01204 | $0.02883 | $0.08048 |
| 51 | $0.01205 | $0.02915 | $0.08222 |
| 52 | $0.01207 | $0.02945 | $0.08389 |
| 53 | $0.01209 | $0.02975 | $0.08550 |
| 54 | $0.01210 | $0.03003 | $0.08705 |
| 55 | $0.01212 | $0.03030 | $0.08854 |
| 56 | $0.01214 | $0.03075 | $0.09110 |
| 57 | $0.01216 | $0.03118 | $0.09358 |
| 58 | $0.01218 | $0.03159 | $0.09596 |
| 59 | $0.01220 | $0.03199 | $0.09827 |
| 60 | $0.01222 | $0.03238 | $0.10050 |
| 61 | $0.01225 | $0.03300 | $0.10423 |
| 62 | $0.01227 | $0.03360 | $0.10784 |
| 63 | $0.01229 | $0.03419 | $0.11134 |
| 64 | $0.01231 | $0.03475 | $0.11473 |
| 65 | $0.01233 | $0.03530 | $0.11801 |
| 66 | $0.01236 | $0.03586 | $0.12139 |
| 67 | $0.01238 | $0.03642 | $0.12486 |
| 68 | $0.01240 | $0.03700 | $0.12844 |
| 69 | $0.01242 | $0.03758 | $0.13211 |
| 70 | $0.01244 | $0.03818 | $0.13589 |
| rb | 6.73% | 8.17% | 11.01% |
| Speed (mph) | Emission Damage Cost (2000 $ per vehicle-mile) | ||
|---|---|---|---|
| Four-Tire Vehicles | Single-Unit Trucks | Combination Trucks | |
| a. Source: estimated by Volpe Center using procedure described in text. | |||
| b. Projected Annual Rate of Decline after year 2000. | |||
| 5 | $0.02662 | $0.04779 | $0.11686 |
| 6 | $0.02363 | $0.04437 | $0.11087 |
| 7 | $0.02150 | $0.04193 | $0.10659 |
| 8 | $0.01989 | $0.04010 | $0.10338 |
| 9 | $0.01865 | $0.03868 | $0.10088 |
| 10 | $0.01765 | $0.03754 | $0.09889 |
| 11 | $0.01696 | $0.03617 | $0.09562 |
| 12 | $0.01639 | $0.03502 | $0.09290 |
| 13 | $0.01590 | $0.03406 | $0.09060 |
| 14 | $0.01548 | $0.03323 | $0.08863 |
| 15 | $0.01512 | $0.03251 | $0.08692 |
| 16 | $0.01475 | $0.03178 | $0.08492 |
| 17 | $0.01441 | $0.03113 | $0.08316 |
| 18 | $0.01412 | $0.03055 | $0.08160 |
| 19 | $0.01385 | $0.03004 | $0.08020 |
| 20 | $0.01362 | $0.02958 | $0.07894 |
| 21 | $0.01341 | $0.02918 | $0.07773 |
| 22 | $0.01323 | $0.02883 | $0.07663 |
| 23 | $0.01306 | $0.02851 | $0.07563 |
| 24 | $0.01290 | $0.02821 | $0.07471 |
| 25 | $0.01276 | $0.02793 | $0.07386 |
| 26 | $0.01264 | $0.02774 | $0.07322 |
| 27 | $0.01252 | $0.02757 | $0.07261 |
| 28 | $0.01242 | $0.02740 | $0.07206 |
| 29 | $0.01232 | $0.02725 | $0.07154 |
| 30 | $0.01223 | $0.02711 | $0.07105 |
| 31 | $0.01215 | $0.02705 | $0.07086 |
| 32 | $0.01208 | $0.02700 | $0.07067 |
| 33 | $0.01202 | $0.02695 | $0.07050 |
| 34 | $0.01196 | $0.02690 | $0.07033 |
| 35 | $0.01190 | $0.02685 | $0.07018 |
| 36 | $0.01190 | $0.02689 | $0.07039 |
| 37 | $0.01191 | $0.02693 | $0.07058 |
| 38 | $0.01191 | $0.02696 | $0.07077 |
| 39 | $0.01191 | $0.02700 | $0.07095 |
| 40 | $0.01192 | $0.02703 | $0.07112 |
| 41 | $0.01193 | $0.02716 | $0.07174 |
| 42 | $0.01194 | $0.02728 | $0.07234 |
| 43 | $0.01195 | $0.02740 | $0.07291 |
| 44 | $0.01196 | $0.02752 | $0.07345 |
| 45 | $0.01197 | $0.02763 | $0.07397 |
| 46 | $0.01199 | $0.02784 | $0.07508 |
| 47 | $0.01200 | $0.02804 | $0.07614 |
| 48 | $0.01201 | $0.02823 | $0.07715 |
| 49 | $0.01202 | $0.02842 | $0.07812 |
| 50 | $0.01204 | $0.02860 | $0.07905 |
| 51 | $0.01205 | $0.02891 | $0.08076 |
| 52 | $0.01207 | $0.02920 | $0.08240 |
| 53 | $0.01209 | $0.02949 | $0.08398 |
| 54 | $0.01210 | $0.02976 | $0.08550 |
| 55 | $0.01212 | $0.03002 | $0.08697 |
| 56 | $0.01214 | $0.03045 | $0.08948 |
| 57 | $0.01216 | $0.03087 | $0.09191 |
| 58 | $0.01218 | $0.03127 | $0.09425 |
| 59 | $0.01220 | $0.03166 | $0.09651 |
| 60 | $0.01222 | $0.03203 | $0.09870 |
| 61 | $0.01225 | $0.03263 | $0.10236 |
| 62 | $0.01227 | $0.03321 | $0.10591 |
| 63 | $0.01229 | $0.03377 | $0.10934 |
| 64 | $0.01231 | $0.03431 | $0.11266 |
| 65 | $0.01233 | $0.03484 | $0.11588 |
| 66 | $0.01235 | $0.03538 | $0.11919 |
| 67 | $0.01238 | $0.03592 | $0.12260 |
| 68 | $0.01240 | $0.03648 | $0.12610 |
| 69 | $0.01242 | $0.03704 | $0.12971 |
| 70 | $0.01244 | $0.03761 | $0.13342 |
| rb | 6.73% | 8.17% | 10.95% |