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Suggested Citation:"F Transportation System Management." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
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Appendix F
Transportation System Management

The basis for the calculation of cost-effectiveness for one possible parking management program is presented here. The program considered would address the CO2 emissions of some of the 48 million people in U.S. metropolitan areas who drive to work alone (Pisarski, 1987). Currently, three-quarters of them, or 36 million, are provided with free parking by their employers (Pucher, 1988). Under this parking management program, 25 percent, or 9 million, of these spaces would be physically eliminated by the year 1995. Parking fees or surcharges would be imposed on the remaining 75 percent, or 27 million spaces, set at a level designed to reduce the proportion of persons driving alone by 15 percent, from 65 percent (Pisarski, 1987) to 50 percent by 1995.

As calculated below, this proposal would produce an annual CO2 reduction of 49 megatons (Mt) at a cost of between -$4.75 and $2.59 billion.1 Cost-effectiveness thus ranges from -$97/t CO2 to $53/t CO2, for an average value of -$22/t CO2.

Calculation of CO2 Emission Reductions

The first step is to calculate the annual CO2 emissions attributable to different commuter transportation modes (see Table F.1). Calculations are performed for a 10-mile commuting trip, which is the national average (Pisarski, 1987).

The second step is to calculate the way in which solo commuters will redistribute themselves among alternative transportation modes in response to parking restrictions. This analysis assumes that the percentage of those who use bus, rail, carpool, or vanpool will be proportional to the current "mode split" (excluding pedestrians and those who work at home). Where

Suggested Citation:"F Transportation System Management." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
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TABLE F.1 Carbon Dioxide Emissions by Commuting Mode (tons/year)

Mode

Btu per Passenger Milea

Yearly Energy (MBtu)b

Equivalent Gallons Gasolinec

Amount of Yearly CO2 Emissionsd

Difference from Solo Driving

Solo driving

8,333

41.66

333.3

2.98

Bus

2,121

14.77

118.2

1.06

1.92

Rail

1,935

13.84

110.7

0.99

1.99

Carpool

3,788

18.94

151.5

1.36

1.62

Vanpool

882

8.58

68.6

0.61

2.37

aFor solo drivers, the figure is per vehicle-mile for automobile commuting.

bEnergy use = (Btu per passenger-mile) × (10 miles per commuting trip) × (2 trips per day) × (250 commuting days per year). In addition, for bus, rail, and vanpool modes, it is assumed that commuters drive alone 1 mile (at 8333 Btu/mi) each way per day to get to the transfer point. For rail, energy use for commuter rail is used (rather than the lower energy use for transit rail).

cAssumes that 1 gallon of gasoline = 125,000 Btu (Davis et al., 1989).

d(Gasoline usage) × (19.7 lbs CO2/gal gasoline)/(2200 lb/t).

parking spaces are eliminated, it is assumed that none of the 9 million displaced solo commuters continue to drive alone, and all are divided among the four remaining modes. Where parking spaces are priced to reduce the solo driver mode share to 50 percent, the shares for the remaining modes are proportional to those calculated for elimination of parking spaces. (To account for the remaining solo drivers, the other mode shares add up to 50 percent, rather than 100 percent, of all commuters.) The mode splits for displaced drivers are presented in Table F.2.

These mode splits are then applied to the 9 million solo drivers affected by the parking elimination component and the 27 million solo drivers affected by the parking management component. As shown in Table F.3, the combination of these two measures would produce annual emission reductions of 49 Mt of CO2.

Calculation of Cost-Effectiveness

A parking demand management program of the type described in this appendix would involve several types of costs and savings:

• employees' out-of-pocket costs or savings from the use of alternative transportation modes (a figure that includes fuel savings);

• employers' out-of-pocket operational costs or savings from parking management and provision of transportation alternatives;

Suggested Citation:"F Transportation System Management." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
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TABLE F.2 Calculation of Mode Shares for Multiple Occupancy Vehicle Modes When Parking Spaces Are Eliminated or Restricted

   

Current Mode Share (%)

Elimination—Adjusted Mode Share (%)a

Surcharge—Adjusted Mode Share (%)b

Solo driving

64.4

0.0

50.0

Public transit

     
 

Bus

5.2

19.3

9.6

 

Rail

2.8

10.4

5.2

Group ridec

     
 

Carpool

16.8

62.2

31.1

 

Vanpool

2.2

8.1

4.1

aAssumes no solo driving; share of each mode when considering only the 20.09 million metropolitan commuters currently commuting by bus, rail, and group (carpool and vanpool) ride (Pisarski, 1987).

bAssumes 50 percent solo driving; share of other modes calculated by halving adjusted mode shares calculated (in column 2) when all solo driving is eliminated.

cPisarski (1987) gives the "group ride" mode share as 19 percent but does not give separate mode shares for carpooling and vanpooling. The assumed mode shares are based on the proportion of carpooling to vanpooling in Table 3-17 of Pisarski (1987) (20.1 percent carpooling versus 2.6 percent vanpooling) and the census estimate that 1.6 million people used vanpools in 1980.

TABLE F.3 Carbon Dioxide Emission Reductions from Parking Management Program

Mode

New Passenger Trips—Parking Elimination (million trips/yr)a

New Passenger Trips—Parking Surcharge (million trips/yr)b

Total New Passenger Trips (million trips/yr)c

CO2 Emission Reduction (Mt/yr)

Bus

1.74

2.59

4.33

8.31

Rail

0.94

1.40

2.34

4.66

Carpool

5.59

8.40

13.99

33.16

Vanpool

0.73

1.11

1.84

2.98

 

TOTAL

9.0

13.5

22.5

49.05

aApplication of mode shares from table F.2 to 9 million solo drivers affected by elimination of parking spaces.

bApplication of mode shares from Table F.2 to 27 million solo drivers affected by surcharges on parking spaces, 13.5 million of them continue to solo commute.

cMultiply total new trips for each mode by CO2 emission reductions, compared to solo driving, from Table F.1.

Suggested Citation:"F Transportation System Management." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
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Page 762

• employers' capital savings from the avoided costs of constructing parking spaces; and

• monetized costs or savings from changes in the lengths of commuting trips.

The first category—employees' out-of-pocket costs—is calculated by considering costs such as variable automobile operating expenses, bus and train fares, and vanpool fees. The second category—employers' operational costs—involves increased costs for running carpool and vanpool programs, offset by savings from avoiding the annual operating and maintenance costs of providing parking spaces for bus, rail, and some ridesharing commuters. The third category—employers' capital savings—represents the avoided costs of constructing parking spaces at an average investment of $3000 per space. Finally, changes in the length of commuting trips cause productivity losses or gains that can be monetized.

TABLE F.4 Combined Employer/Employee Out-of-Pocket Costs/Savings of Alternative Commuting Modes per Daily Round Trip Commute (1987 dollars)

Mode

Worker Cost ($)

Employer Cost ($)

Total Cost ($)

Difference from Solo Driving ($)

Solo driving

1.44a

0.26b

1.70

Bus

1.24c

-0.26d

0.98

-0.72

Commuter rail

2.60e

-0.26d

2.34

0.64

Carpool

0.65f

-0.22g

0.87

-0.83

Vanpool

2.40h

0.04i

2.44

0.74

aBased on 7.31 cents per mile for 1987 variable operating costs of an automobile (Davis et al., 1989) for 20-mile round trip.

bBased on average employer cost of $64 per year to operate a parking space (Wegmann, 1989).

cRounded, based on 1987 average one-way transit trip cost of $0.62 (U.S. DOT, 1989).

dEmployer savings from not providing a parking space for bus rail riders.

eBased on 1987 average commuter rail fare equivalent to $0.13 per mile (U.S. DOT, 1989) for a 20-mile round trip.

fAssumes that an average of 2.2 persons (Pisarski, 1987) splits the cost of solo driving.

gBased on providing 1/2.2 (average carpool occupancy) of a parking space and administrative costs of $25 per employee for carpool matching program.

hBased on monthly fare of $50 per vanpool rider (Toruemke and Roseman, 1989).

iBased on providing 1/10.7 (average vanpool occupancy) of a parking space and employer administrative costs of $4.50 per employee per year for running vanpool program.

Suggested Citation:"F Transportation System Management." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
×

Page 763

TABLE F.5 Out-of-Pocket Employee and Employer Savings from Switching from Solo Driving to Other Commuting Modes

Mode

New Passenger Trips (million)a

Commuting Cost Differential ($ billion)b

Bus

4.33

-3.12

Rail

2.34

1.50

Carpool

13.99

-11.61

Vanpool

1.84

1.36

 

TOTAL

 

-11.87

NOTE: Not counting avoided cost of constructing parking spaces and productivity gains/losses.

aFrom Table F.3.

bNumber of new passenger trips multiplied by cost differential per trip from Table F.4.

The first two categories of costs are elaborated in Table F.4. Once the cost per commuter trip for each mode is calculated, the total out-of-pocket costs/savings of a parking management program are calculated by multiplying the number of former solo commuters using each alternative mode by the cost differential. The results are presented in Table F.5. Savings to both workers and employers exceed costs, resulting in an overall program savings of -$12 million.

In addition to these savings, employers save money by avoiding the capital costs of providing parking. Constructing a parking space costs between $1,000 and $15,000 (Institute of Transportation Engineers, 1989), with one survey finding an average cost for added spaces of $3,920 (Wegmann, 1988). Even if a space has already been constructed, employers can realize savings from eliminating the use of the space for employee parking and using the space for paid, commercial parking or other purposes. This parking management program would eliminate the need for 16.9 million parking spaces, 9 million directly eliminated and 7.9 million freed when solo commuters shift to less parking-intensive modes. If only 10 percent (or 1.69 million parking spaces) are spaces that would otherwise have been built at an average construction cost of $3000, the total employer capital cost savings is $5.1 billion.

Finally, the program will change the length of commuting trips in two ways. First, traffic congestion will be reduced because 22.5 million solo commuting cars will be replaced by 6.7 million buses, carpools, vanpools,

Suggested Citation:"F Transportation System Management." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
×

Page 764

TABLE F.6 Changes in Annual Commuting Time for Different Modes Relative to Base-Case Solo Commuting Without Parking Management

   

5 Percent Increase in Speedb

20 Percent Increase in Speedc

Mode

Base-Case Speeda (mph)

Speed (mph)

Delay/Savings (hours)d

Speed (mph)

Delay/Savings (hours)d

Solo driving

32

34

(8)

38

(25)

Bus

13

14

200

16

150

Rail

23

23

58

26

58

Carpool

32

34

(8)

38

(25)

Vanpool

29

30

(8)

35

(17)

aTravel speeds for solo driver, bus, and rail are from Table 3-23 in Pisarski (1987). Although Pisarski lists the speed for carpoolers at a faster 34 mph, this was adjusted to 32 mph to account for pickups/drop-offs. The speed for vanpooling was estimated at 10 percent slower than carpooling to account for additional pickups/drop-offs.

bThis case assumes that travel speeds for highway modes (solo driver, bus, carpool, and vanpool) increase 5 percent relative to the base case due to reduced traffic congestion.

cThis case assumes that travel speeds for highway modes (solo driver, bus, carpool, and vanpool) increase 20 percent relative to the base case due to reduced traffic congestion.

dTime delays/savings are compared to the base case for solo commuters. Annual travel time is based on 250 round-trip commutes annually, with an average trip length of 10 miles each way (Pisarski, 1987).

and solo commuters. With one-third fewer commuter vehicles on the road during peak hours (there are currently 48 million solo commuters in metropolitan areas of the United States), traffic congestion will be reduced and travel speeds increased for all highway modes (solo drivers, carpools, vanpools, buses). This analysis considers two scenarios, one in which travel speed is increased by 5 percent and one in which travel speed is increased by 20 percent.

Trip lengths will also change because shifting to modes such as buses and vanpools will increase commuting times relative to solo automobile travel. Data presented in Pisarski (1987) indicate that commuting by bus and rail is slower than commuting by automobile. Table F.6 calculates the relative changes in annual commuting time accounting for both of these factors. Table F.7 then converts these figures into total commuting time delays/gains and monetizes the resulting productivity changes at values ranging from $5 to $10 per hour. These figures are consistent with values of $5 to

Suggested Citation:"F Transportation System Management." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
×

Page 765

TABLE F.7 Monetized Value of Changes in Trip Lengths Due to Parking Management Program Relative to Base-Case Solo Commuting

     

5 Percent Increase in Speedb

20 Percent Increase in Speedc

Mode

Number of New Passenger Trips (million trips/year)a

Change in Travel Time (hours/persons/yr)d

Change in Value of Travel Time (G$/yr)e

Change in Travel Time (hours/persons/yr)d

Change in Value of Travel Time (G$/yr)f

Solo driving

13.50

(8)

(1.08)

(25)

(1.69)

Bus

4.33

200

8.66

150

3.25

Rail

2.34

58

1.36

58

0.68

Carpool

13.99

(8)

(1.12)

(25)

(1.75)

Vanpool

1.84

(8)

(0.15)

(17)

(0.16)

 

TOTAL

   

7.67

 

0.33

aFrom Table F.3.

bThis case assumes that travel speeds for highway modes (solo driver, bus, carpool, and vanpool) increase 5 percent relative to the base case due to reduced traffic congestion.

cThis case assumes that travel speeds for highway modes (solo driver, bus, carpool, and vanpool) increase 20 percent relative to the base case due to reduced traffic congestion.

dFrom Table F.6.

eEach hour of change in travel is valued at $10, as explained in the text. Total savings is (number of passenger trips) × (hours of delay or savings) × ($10 per hour).

fEach hour of change in travel is valued at $5, as explained in the text. Total savings is (number of passenger trips) × (hours of delay or savings) × ($5 per hour).

Suggested Citation:"F Transportation System Management." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
×

Page 766

$7 per hour used by the Federal Highway Administration and transportation researchers to value time spent in traffic delays (U.S. General Accounting Office, 1989; Wegmann, 1989). (Only the upper-bound and lower-bound cases are presented in Table F.7; the lower bound assumes a 20 percent increase in highway speed and values delays at $5 per hour, while the upper bound assumes a 5 percent increase in highway speed and values delays at $10 per hour.)

Thus the total cost of this parking management program is as follows:

Out-of-pocket costs (employers and employees)

($0.01 billion)

Avoided parking space construction

($5.07 billion)

Productivity gains/losses

$0.33 billion to $7.67 billion

The total cost thus ranges from -$4.75 billion to $2.59 billion.

Note

1. Throughout this report, tons (t) are metric; 1 Mt = 1 megaton = 1 million tons.

References

Davis, S. C., D. B. Shonka, G. J. Anderson-Batiste, and P. S. Hu. 1989. Transportation Energy Data Book: Edition 10. Report ORNL-6565 (Edition 10 of ORNL-5198). Prepared for the U.S. Department of Energy. Oak Ridge, Tenn.: Oak Ridge National Laboratory.

Institute of Transportation Engineers. 1989. A Toolbox for Alleviating Traffic Congestion. Washington. D.C.: Institute of Transportation Engineers.

Pisarski, A. 1987. Commuting in America: A National Report on Commuting Patterns and Trends. Westport, Connecticut: Eno Foundation for Transportation.

Pucher, J. 1988. Urban travel behavior as the outcome of public policy: The example of modal split in Western Europe and North America. The Journal of American Planners Association 54(4):509–520.

Toruemke, D., and D. Roseman. 1989. Vanpools: Pricing and market penetration. Transportation Research Record. 122:83–87.

U.S. Department of Transportation. 1989. National Transportation Statistics. Washington, D.C.: U.S. Department of Transportation.

U.S. General Accounting Office (GAO). 1989. Traffic Congestion: Trends, Measures and Effects. Washington, D.C.: U.S. General Accounting Office.

Wegmann, F. 1989. Cost-effectiveness of private employer ridesharing programs: An employer's assessment. Transportation Researh Record 1212:88–100.

Suggested Citation:"F Transportation System Management." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
×
Page 759
Suggested Citation:"F Transportation System Management." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
×
Page 760
Suggested Citation:"F Transportation System Management." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
×
Page 761
Suggested Citation:"F Transportation System Management." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
×
Page 762
Suggested Citation:"F Transportation System Management." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
×
Page 763
Suggested Citation:"F Transportation System Management." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
×
Page 764
Suggested Citation:"F Transportation System Management." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
×
Page 765
Suggested Citation:"F Transportation System Management." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
×
Page 766
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Global warming continues to gain importance on the international agenda and calls for action are heightening. Yet, there is still controversy over what must be done and what is needed to proceed.

Policy Implications of Greenhouse Warming describes the information necessary to make decisions about global warming resulting from atmospheric releases of radiatively active trace gases. The conclusions and recommendations include some unexpected results. The distinguished authoring committee provides specific advice for U.S. policy and addresses the need for an international response to potential greenhouse warming.

It offers a realistic view of gaps in the scientific understanding of greenhouse warming and how much effort and expense might be required to produce definitive answers.

The book presents methods for assessing options to reduce emissions of greenhouse gases into the atmosphere, offset emissions, and assist humans and unmanaged systems of plants and animals to adjust to the consequences of global warming.

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