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TABLE OF CONTENTS

LIST OF TABLES ...................................................................................................................... vii

LIST OF FIGURES ..................................................................................................................... xi

INTRODUCTION ........................................................................................................................ 1

PROFILE OF THE 1995 NPTS ................................................................................................... 2

IMPROVEMENTS IN THE 1995 NPTS SURVEY METHOD ................................................. 3

REPORT ORGANIZATION ....................................................................................................... 4

TRAVEL AND DEMOGRAPHIC SUMMARY ........................................................................ 7

HOUSEHOLD TRAVEL ........................................................................................................... 12

PERSON TRAVEL .................................................................................................................... 17

PRIVATE VEHICLE TRAVEL ................................................................................................ 26

VEHICLE AVAILABILITY AND UTILIZATION ................................................................. 28

COMMUTE TRAVEL PATTERNS ......................................................................................... 39

TEMPORAL DISTRIBUTION .................................................................................................. 46

TRAVEL BEHAVIOR OF SUB-POPULATIONS .................................................................. 49

REFERENCES ........................................................................................................................... 54

TRAVEL CONCEPTS AND GLOSSARY OF TERMS ...................................................... G-1

APPENDIX 1. CHANGES IN THE 1995 NPTS SURVEY METHODOLOGY

 AND THEIR PROBABLE IMPACTS ............................................................................ A1-1

APPENDIX 2. ADJUSTMENT OF 1990 TRAVEL DATA ............................................... A2-1

	


 
!

APPENDIX 3. DIFFERENCES IN WORKERS AND COMMUTE TRIPS

 BETWEEN 1990 AND 1995 NPTS ................................................................................. A3-1

APPENDIX 4. DIFFERENCES IN METROPOLITAN AREA DEFINITIONS

 BETWEEN 1983 AND 1990 NPTS ................................................................................. A4-1

APPENDIX 5. STANDARD ERROR TABLES ................................................................. A5-1

APPENDIX 6. SEGMENTED TRIPS IN NPTS .................................................................. A6-1

APPENDIX 7. REVISED AVERAGE ANNUAL MILES DRIVEN PER DRIVER ........ A7-1

 	



!

LIST OF TABLES

Travel and Demographic Summary

Table 1. Summary Statistics on Demographic Characteristics and Total Travel,

1969, 1977, 1983, 1990, and 1995 NPTS ................................................................. 7

Table 2. Summary Demographic and Travel Trends, 1969, 1977, 1983, 1990,

and 1995 NPTS ......................................................................................................... 9

Table 3. Comparison of Survey Variables with Other Sources .............................................. 11

Household Travel

Table 4. Average Annual PMT, Person Trips and Trip Length by Trip Purpose,

1983, 1990, and 1995 NPTS ................................................................................... 12

Table 5. Average Annual VMT, Vehicle Trips and Trip Length by Selected Trip

Purposes, 1969, 1977, 1983, 1990, and 1995 NPTS ............................................... 13

Table 6. Average Annual Person Trips per Household by Mode of Transportation

and MSA Size, 1977, 1983, 1990, and 1995 NPTS ................................................ 14

Table 7. Person Trips per Household by Household Income, 1983, 1990,

and 1995 NPTS ....................................................................................................... 16

Person Travel

Table 8. Total Person Trips by Mode of Transportation and Trip Purpose,

Adjusted 1990 and 1995 NPTS ............................................................................... 17

Table 9. Person Trips per Person by Trip Purpose and Gender,

Adjusted 1990 and 1995 NPTS ............................................................................... 18

	


 
!

Table 10. Daily Trip Rates per Person by Trip Purpose, 1977, 1983, 1990,

and 1995 NPTS ....................................................................................................... 20

Table 11. Distribution of Daily Person Miles of Travel per Person by Mode of

Transportation and Trip Purpose, Adjusted 1990 and 1995 NPTS .......................... 21

Table 12. Average Daily Person Trips per Person by Age and Gender,1983, 1990,

and 1995 NPTS ....................................................................................................... 22

Table 13. Average Daily Person Miles of Travel per Person by Age and Gender,

1983, 1990, and 1995 NPTS ................................................................................... 24

Private Vehicle Travel

Table 14. Average Time Spent Driving a Private Vehicle in a Typical Day by MSA Size,

Adjusted 1990 and 1995 NPTS ............................................................................... 26

Table 15. Average Vehicle Occupancy for Selected Trip Purposes,

1977, 1983, 1990, and 1995 NPTS ......................................................................... 27

Vehicle Availability and Utilization

Table 16. Availability of Household Vehicles, 1969, 1977, 1983, 1990,

and 1995 NPTS ....................................................................................................... 28

Table 17. Distribution of Households by Household Vehicle Availability and

Population Density, 1990 and 1995 NPTS .............................................................. 30

Table 18. Percent of Households Without a Vehicle Within MSA Size Group,

1977, 1983, 1990 and 1995 NPTS .......................................................................... 32

Table 19. Vehicle Distribution and Average Vehicle Age by Vehicle Type,

1977, 1983, 1990, and 1995 NPTS ......................................................................... 33

 	



/

Table 20. Distribution of Vehicles by Vehicle Age and Vehicle Type,

1969, 1977, 1983, 1990, and 1995 NPTS ............................................................... 34

Table 21. Average Annual Miles per Vehicle by Vehicle Age,1969, 1977, 1983,

1990, and 1995 NPTS ............................................................................................. 36

Table 22. Average Annual Miles per Licensed Driver by Driver Age and Gender,

1969, 1977, 1983, 1990, and 1995 NPTS ............................................................... 38

Commute Travel Patterns

Table 23. Commute VMT and Total VMT By Year, 1969, 1977,

1983, 1990, and 1995 NPTS ................................................................................... 39

Table 24. Distribution of Workers by Usual Mode, 1969, 1977, 1983, 1990,

and 1995 NPTS ....................................................................................................... 41

Table 25. General Commute Patterns by Mode of Transportation, 1983, 1990,

and 1995 NPTS ....................................................................................................... 42

Table 26. Average Commute Speed by MSA Size, 1983, 1990, and 1995 NPTS .................. 44

Temporal Distribution

Table 27. Distribution of Person Trips by Start Time of Trip, 1983, 1990,

and 1995 NPTS ....................................................................................................... 46

Table 28. Daily Travel Statistics by Weekday vs Weekend, Adjusted 1990

and 1995 NPTS ....................................................................................................... 48

Travel Behavior of Sub-Populations

Table 29. Daily Travel Statistics of People 65 and Older, 1983, 1990, and 1995 NPTS ......... 49

	


 
/

Table 30. Daily Person Trips of Adult Women by Household Composition,

1983, 1990, and 1995 NPTS ................................................................................... 50

Table 31. Daily Person Trips per Person for Low Income Households by Trip Purpose,

1983, 1990, and 1995 NPTS ................................................................................... 51

Table 32. Daily Person Trips per Person by Vehicle Ownership Status and MSA Size,

Adjusted 1990 and 1995 NPTS ............................................................................... 52

 	



/

LIST OF FIGURES

Travel and Demographic Summary

Figure 1. Changes in Summary Demographics, 1969, 1977, 1983, 1990, and 1995 NPTS .......8

Household Travel

Figure 2. Percent Trips by Public Transportation per Household by MSA Size,

Adjusted 1990 and 1995 NPTS .................................................................................15

Person Travel

Figure 3. Distribution of Person Trips per Person by Gender and Trip Purpose,

Adjusted 1990 and 1995 NPTS .................................................................................19

Figure 4. Percent Change per Person in Personal Travel by Age and Gender

From Adjusted 1990 to 1995 .....................................................................................23

Figure 5. Average Daily Person Miles of Travel per Person by Gender,

Adjusted 1990 and 1995 ............................................................................................25

Vehicle Availability and Utilization

Figure 6. Household Distribution by Household Income and Vehicle to Driver Ratio,

1995 NPTS ................................................................................................................29

Figure 7. Vehicle Ownership and Demographic Statistics by Population Density,

1995 NPTS ................................................................................................................31

Figure 8. Distribution of Vehicles by Vehicle Age, 1969, 1977, 1983, 1990

and 1995 NPTS .........................................................................................................35

	


 	
/

Figure 9. Annual Miles Driven Per Vehicle, Indexed to the Annual Average,

1969, 1977, 1983, 1990 and 1995 NPTS ................................................................... 37

Commute Travel Patterns

Figure 10. Distribution of Workers by Usual Mode, 1995 NPTS ................................................ 40

Figure 11. Average Travel Time for Commuting by Selected Travel Mode and MSA Size,

1995 NPTS ................................................................................................................. 43

Figure 12. Average Commute Speed for Selected Time of Day by MSA Size,

1995 NPTS ................................................................................................................. 45

Temporal Distribution

Figure 13. Distribution of Person Trips by Trip Purpose and Start Time of Trip,

1995 NPTS ................................................................................................................. 47

Travel Behavior of Sub-Populations

Figure 14. Mode Distribution of Person Trips Taken by Zero-Vehicle Households,

1995 NPTS ................................................................................................................. 53

	 	



SUMMARY OF TRAVEL TRENDS

1995 NATIONWIDE PERSONAL TRANSPORTATION SURVEY
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Summary of Travel Trends

1995 Nationwide Personal Transportation Survey

INTRODUCTION

“The national objectives of general welfare, economic growth and stability, and

security of the United States require the development of transportation policies and

programs that contribute to providing fast, safe, efficient, and convenient

transportation at the lowest cost consistent with those and other national objectives,

including the efficient use and conservation of the resources of the United States.”

- U.S. DOT Strategic Plan for Fiscal Years 1997-2002

To reach these objectives, five specific performance goals are identified: safety, mobility, economic

growth and trade, human and natural environment, and national security. To develop transportation

policies and programs that reach these goals, it is imperative to fully understand how travel behavior

changes over time.

To further our understanding of travel behavior, the U.S. Department of Transportation (US DOT)

conducts the Nationwide Personal Transportation Survey (NPTS) to obtain information on personal

travel of U.S. households with respect to why, how, when, where from, where to, how frequently, how

long, and with whom. The NPTS also provides information by subgroups of the population, e.g., by

age, gender, race, zero-vehicle households, which allows important policy analyses of how

transportation serves these groups. The NPTS has been conducted in 1969, 1977, 1983, 1990, and

1995.

	


 	
PROFILE OF THE 1995 NPTS

Coverage. The NPTS is a survey of travel by the civilian, non-institutionalized population of the

United States age five and older. As such, it does not include: (1) military personnel

living on base or overseas, and (2) residents of group quarters, such as nursing homes

or assisted-living facilities, college dormitories, long-term medical institutions, and

prisons. However, military personnel are included if they live in civilian housing.

College students are included if they live in apartments or other off-campus housing, or

if they are contacted when home for the summer.

Sample Size. The sample size for the 1995 NPTS was 42,033 households comprised of:

- a national sample of 21,020 completed households, and

- 21,013 additional households collected for the use of and funded by five

add-on areas:

New York State,

Commonwealth of Massachusetts,

Oklahoma City, Oklahoma,

Tulsa, Oklahoma, and

Seattle, Washington.

The 42,033 households in the NPTS sample contained 103,466 persons eligible for

the survey, of which 95,360 were interviewed.

Contents. The NPTS serves as the nation’s inventory of daily personal travel. It collects data

on the daily trips including, but not limited to:

- purpose of the trip (work, shopping, etc.)

- means of transportation used (car, bus, subway, walk, etc.)

- how long the trip took , i.e., travel time

- time of day the trip took place

	 	





- day of week the trip took place

- number of people in the vehicle , i.e., vehicle occupancy

- driver characteristics (age, gender, worker status, education level, etc.)

- vehicle attributes (make, model, model year, amount of miles driven in a year).

These data are collected for:

- all personal trips

- all modes

- all purposes

- all trip lengths

- all areas of the country, urban and rural

- all days of the week

- all months of the year.

For more information on the 1995 survey methodology and procedures, please consult: “User’s

Guide for the Public Use Data Files 1995 Nationwide Personal Transportation Survey” available

at:

www-cta.ornl.gov/npts/

In addition to being an information resource, this web site allows you to conduct ad hoc analysis. Note

that new users are required to complete a simple registration before using the analysis tools.

IMPROVEMENTS IN THE 1995 NPTS SURVEY METHOD

The US DOT continues to research and embrace improved methodologies to collect more accurate and

more complete travel data, and to increase response rates. Among the changes in the NPTS, two are

especially significant. First, a written diary was used to help respondents to better remember their travel

on their designated travel day. Second, a household roster of trips was used to assist respondents to

	


 	


recall trips made with other household members. A comparison between the 1990 and 1995 survey

methods is summarized in Appendix 1.

While improvements to the survey process are encouraged, changes in the 1995 survey method brought

about significant data compatibility issues. To address these issues, the 1990 survey data were adjusted

to allow comparison to the 1995 survey (see Implications and Adjustment box). Since the survey

improvements helped the reporting of trips that might have been forgotten, the adjustment only applies

to trip frequency and not to trip attributes (e.g., trip length) nor to household, driver and vehicle

characteristics. In this report, both the original 1990 data and the adjusted 1990 data are reported to

facilitate trends analysis. The reader is advised to compare the 1969-1983 survey results to the

unadjusted 1990 data, and the 1995 survey results to the adjusted 1990 data.

REPORT ORGANIZATION

This report highlights important travel trends in tabular and graphic format. Statistics are categorized

by topic. The report begins with a summary of travel and demographic changes. Next, travel changes

are examined from an individual household perspective, then from an individual person perspective.

This report concludes with trip-making statistics of sub-populations such as women, households

without vehicles, low-income households, and the elderly. No attempt is made in this report to present

all of the data or to analyze and discuss the data in any depth. Standard error estimates for key statistics

are presented in Appendix 5.

	 	





	


 	

Implications of Improved Survey Method and Adjustments of 1990 Data

As depicted in Appendix 1, there were a number of changes in the 1995 survey. Changes that

presumably caused the greatest impacts on trip reporting were the use of a written travel diary and

household rosters of trips. The 1990 survey data have been adjusted, to the extent possible, to

account for the potential impacts on travel trends due to these changes.

Three assumptions were used to adjust the 1990 survey data shown in this report. First, it was

assumed that had the improved survey method been used in the 1990 survey, more discretionary

trips would have been reported. Second, it was assumed that the improved survey method would

not have helped the reporting of non-discretionary trips (e.g., work and school trips). Finally, it was

assumed that the adjustment procedure only affects the statistics on the number of trips but not on

the attributes of individual trips (e.g., trip length). For example, it was estimated that an additional

forty-one percent of trips taken for family and personal business, other than shopping, would have

been recorded in the 1990 survey if the improved method had been used.

Based on the adjusted 1990 data, the NPTS survey suggests that Americans increased their travel

by 4.5 percent between 1990 and 1995. This 4.5 percent estimate could be over-estimated because

the impacts of survey changes other than travel diary and trip rostering have not been accounted

for. This implies that almost all of the travel changes observed between the 1990 (even after

adjustment) and 1995 surveys could be slightly over-estimated.


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Table 1

Summary Statistics on Demographic Characteristics and Total Travel

1969, 1977, 1983, 1990, and 1995 NPTS

	




 






 
 
 

 

  	
 	


 

  
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1969 1977 1983 1990 1995

(Indexed to 1969 (1969=1))

Vehicles

Drivers

Workers

Households

Population


	


 	




During the past two decades, the number of vehicles increased at a steeper rate than any other

demographic indicators. In fact, the number of vehicles has increased at an annual rate of almost

one and one-half times that of the total population.

Figure 1

Changes in Summary Demographics

1969, 1977, 1983, 1990, and 1995 NPTS

Note:

• The 1969 NPTS survey did not include trucks as household vehicles. For comparability across surveys, the

number of household vehicles in 1969 was estimated based on statistics reported in Highway Statistics. It was

assumed that fifty percent of all 2-axle 4-tire vehicles in 1969 were used for personal purposes, resulting in a

total estimate 95,876,000 household vehicles [=89,173,502 + 50% × 13,405,772].



	


 
	




On an individual household basis, vehicle ownership seems to have reached a saturation point. By

1990, household vehicle ownership had reached one vehicle for every licensed driver. In terms of

travel, Americans continue to make more vehicle trips and drive more miles.

Table 2

Summary Demographic and Travel Trends

1969, 1977, 1983, 1990, and 1995 NPTS

 1990

1969 1977 1983 1990 Adjusted 1995

Persons per household 3.16 2.83 2.69 2.56 - 2.63

Vehicles per household 1.16 1.59 1.68 1.77 - 1.78

Licensed drivers per household 1.65 1.69 1.72 1.75 - 1.78

Vehicles per licensed driver 0.70 0.94 0.98 1.01 - 1.00

Workers per household 1.21 1.23 1.21 1.27 - 1.33

Vehicles per worker 0.96 1.29 1.39 1.40 - 1.34

Daily vehicle trips per household 3.83 3.95 4.07 4.66 5.69 6.36

Daily VMT per driver 20.64 19.49 18.68 23.69 28.49 32.14

Average vehicle trip length (miles) 8.89 8.34 7.90 8.98 8.85 9.06

Note:

• Average vehicle trip length for 1990 and 1995 is calculated using only those records with trip mileage

information present.

• The 1969 survey does not include pickups and other light trucks as household vehicles.

• Note that only the 1990 data have been adjusted to make them more comparable with the 1995 data. Thus,

there are limits on the conclusions that can be drawn in comparing travel with earlier survey years. The

adjustments to 1990 data affect only person trips, vehicle trips, person miles of travel (PMT) and vehicle miles

of travel (VMT).



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Data on population and on the total number of households are estimated by the

Bureau of Census of the U.S. Department of Commerce as reported in the Statistical Abstract of the United States (1997 edition and previous editions, from Census

Bureau Web page, http://www.census.gov). While the NPTS estimates household

population, the Bureau of Census measures resident and civilian population. The

Bureau of Census’ estimates are for July 1 of each year.

Data on the number of licensed drivers are reported by the Federal Highway Administration (FHWA) of the US DOT in its annual Highway Statistics (Summary

to 1995, Table DL-220, p-III-10). Note that Highway Statistics shows the cumulative number of driver’s licenses issued, while the NPTS estimates the number of

people who hold a driver’s license. (The Highway Statistics series can be found at:

www.fhwa.dot.gov/ohim/ohimstat.htm.)

The NPTS’s estimate on vehicles includes all household-based vehicles but excludes most fleet vehicles, whereas Highway Statistics (Summary to 1995, Table

VM-201A, p-V-17-V-18) reports all vehicles (personal and commercial) categorized by vehicle type (e.g., automobiles, 2-axle, 4-tire trucks, etc.). To estimate

comparable “household-based” vehicles from Highway Statistics, all of the automobiles, motorcycles, and a percentage of the 2-axle 4-tire trucks are assumed to

be household-based vehicles. The percent 2-axle 4-tire trucks used for personal

purposes is estimated from the Truck Inventory and Use Surveys (TIUS) and varies by year:

1977: 63.21 percent trucks, from 1977 TIUS

1983: 64.20 percent trucks, from 1982 TIUS

1990: 72.38 percent trucks, from 1990 TIUS

1995: 73.90 percent trucks, from 1992 TIUS


	


 	



	


 
	




Table 3

Comparison of Survey Variables with Other Sources

(thousands)

Households Population Licensed Vehicles

 Drivers

1969

Other Sources 61,806 199,145 108,306 89,174

NPTS 62,504 197,213 102,986 72,500

1977

Other Sources 74,142 218,106 138,121 132,155

NPTS 75,412 213,141 127,552 120,098

1983

Other Sources 83,918 232,086 154,389 152,070

NPTS 85,371 229,453 147,015 143,714

1990

Other Sources 91,947 247,826 167,015 172,902

NPTS 93,347 239,416 163,025 165,221

1995

Other Sources 97,386 261,538 176,628 180,735

NPTS 98,990 259,994 176,330 176,067

Note:

• See Page 10 for details on other sources.

• The 1969 NPTS survey includes only automobiles, station wagons, and van buses/minibuses as household

vehicles.
	 	




The average household size remained relatively stable, about 2.6 persons per household, from 1990

to 1995 (Table 2). However, a typical household traveled about 4,000 miles more in 1995 than in

1990. This increase took the form of more, but shorter trips for most trip purposes. The notable

exceptions were trips to work and shopping trips, which increased in length. Social and recreational

trips increased in number, but not in miles.

Table 4

Average Annual PMT, Person Trips and Trip Length by Trip Purpose

1983, 1990, and 1995 NPTS

Trip Purpose 1983 1990 1990 1995

Adjusted

Average Annual PMT per Household

All Purposes 22,802 24,803 30,316 34,459

To/From Work 4,586 5,637 5,637 7,740

Work Related Business 1,354 1,043 1,043 1,987

Shopping 2,567 2,674 3,343 4,659

All Other Fam/Per Business 3,311 5,083 7,167 7,381

School/Church 1,522 1,599 1,599 1,973

Social and Recreational 8,964 8,567 11,308 10,571

Other 500 195 214 131

Average Annual Person Trips per Household

All Purposes 2,628 2,673 3,262 3,828

To/From Work 537 539 539 676

Work Related Business 62 38 38 100

Shopping 474 504 630 775

All Other Fam/Per Business 456 606 854 981

School/Church 310 304 304 337

Social and Recreational 728 662 874 953

Other 61 20 22 6

Average Person Trip Length (miles)

All Purposes 8.68 9.45 9.47 9.13

To/From Work 8.54 10.65 10.65 11.63

Work Related Business 21.77 28.20 28.20 20.28

Shopping 5.41 5.38 5.38 6.08

All Other Fam/Per Business 7.27 8.55 8.55 7.63

School/Church 4.90 5.39 5.39 5.98

Social and Recreational 12.31 13.19 13.19 11.27

Other 8.22 10.30 10.30 22.83

Note:

• Average person trip length for 1990 and 1995 is calculated using only those records with trip mileage information present.

• All tables reporting totals could include some unreported characteristics.

• Standard Errors for 1995 data in Table 4 are presented in Appendix 5.

• Note that only the 1990 data have been adjusted to make them more comparable with the 1995 data. Thus, there are limits on

the conclusions that can be drawn in comparing travel with earlier survey years. The adjustments to 1990 data affect only

person trips, vehicle trips, person miles of travel (PMT) and vehicle miles of travel (VMT).


	


 	

In 1995, commuting had the largest share of vehicle travel for all purposes. In the past, social and

recreational trips had the longest average driving distance among all trips. However, this pattern

changed in 1995, with commuting trips becoming the longest. Note also that the increase in the

number of work trips is likely due to the increase in the number of workers in the household

(Table 2).

Table 5

Average Annual VMT, Vehicle Trips and Trip Length by Selected Trip Purposes

1969, 1977, 1983, 1990, and 1995 NPTS

Trip Purpose 1969 1977 1983 1990 1990 1995

Adjusted

Average Annual VMT per Household

All Purposes 12,423 12,036 11,739 15,100 18,161 20,895

To or From Work 4,183 3,815 3,538 4,853 4,853 6,492

Shopping 929 1,336 1,567 1,743 2,178 2,807

Other Fam & Personal Business 1,270 1,444 1,816 3,014 4,250 4,307

Social and Recreational 4,094 3,286 3,534 4,060 5,359 4,764

Average Annual Vehicle Trips per Household

All Purposes 1,396 1,442 1,486 1,702 2,077 2,321

To or From Work 445 423 414 448 448 553

Shopping 213 268 297 345 431 501

Other Fam. & Personal Business 195 215 272 411 579 626

Social and Recreational 312 320 335 349 460 427

Average Vehicle Trip Length (miles)

All Purposes 8.90 8.35 7.90 8.98 8.85 9.06

To or From Work 9.40 9.02 8.55 10.97 10.97 11.80

Shopping 4.36 4.99 5.28 5.10 5.10 5.64

Other Fam. & Personal Business 6.51 6.72 6.68 7.43 7.43 6.93

Social and Recreational 13.12 10.27 10.55 11.80 11.80 11.24

Note:

• Average vehicle trip length for 1990 and 1995 is calculated using only those records with trip mileage information present.

• All purposes includes other purposes not shown above, such as trips to school, church, doctor, dentist, and work-related

business trips.

• All tables reporting totals could include some unreported characteristics.

• Standard Errors for 1995 data in Table 5 are presented in Appendix 5.

• Note that only the 1990 data have been adjusted to make them more comparable with the 1995 data. Thus, there are limits on

the conclusions that can be drawn in comparing travel with earlier survey years. The adjustments to 1990 data affect only

person trips, vehicle trips, person miles of travel (PMT) and vehicle miles of travel (VMT).


	 	




Table 6

Average Annual Person Trips per Household

by Mode of Transportation and MSA Size

1977, 1983, 1990, and 1995 NPTS

Mode of Transportation

SMSA or MSA Size 1977 1983 1990 1990 Adjusted 1995

Private

ALL 2,351 2,152 2,329 2,861 3,307

Not in (S)MSA 2,436 2,322 2,306 2,837 3,492

Less than 250,000 2,517 2,375 2,508 3,090 3,503

250,000 - 499,999 2,574 2,443 2,461 3,014 3,472

500,000 - 999,999 2,628 2,140 2,413 2,957 3,509

1,000,000 - 2,999,999 2,366 2,031 2,430 2,986 3,354

3,000,000 and above 1,785 1,691 2,160 2,649 3,075

PublicTransit

ALL 73 60 52 58 67

Not in (S)MSA 22 11 13 14 9

Less than 250,000 47 17 27 30 23

250,000 - 499,999 44 23 19 22 18

500,000 - 999,999 58 48 28 33 33

1,000,000 - 2,999,999 86 67 46 52 37

3,000,000 and above 189 181 112 124 137

Walk

ALL 261 226 193 234 205

Not in (S)MSA 199 211 146 175 134

Less than 250,000 241 280 172 212 138

250,000 - 499,999 206 199 165 203 152

500,000 - 999,999 256 184 132 161 138

1,000,000 - 2,999,999 295 179 170 207 162

3,000,000 and above 396 330 278 337 301

ALL MODES

ALL 2,808 2,628 2,673 3,262 3,828

Not in (S)MSA 2,800 2,766 2,580 3,151 3,878

Less than 250,000 2,944 2,889 2,816 3,450 3,926

250,000 - 499,999 2,945 2,891 2,741 3,340 3,894

500,000 - 999,999 3,049 2,542 2,667 3,252 3,916

1,000,000 - 2,999,999 2,861 2,463 2,737 3,344 3,795

3,000,000 and above 2,459 2,326 2,641 3,213 3,765

Note:

• The population size groups for 1977 - 1983 NPTS are SMSA Size Groups and 1990 - 1995 are MSA Size Groups (see

Appendix 4).

• All modes includes other modes not specified such as bike, school bus, taxi and other.

• All tables reporting totals could include some unreported characteristics.

• Note that only the 1990 data have been adjusted to make them more comparable with the 1995 data. Thus, there are limits on

the conclusions that can be drawn in comparing travel with earlier survey years. The adjustments to 1990 data affect only

person trips, vehicle trips, person miles of travel (PMT) and vehicle miles of travel (VMT).


0

0.5

1

1.5

2

2.5

3

3.5

4

Not MSA < 250,000 250,000-

499,999

500,000-

999,999

1 - 3 million > 3 million

MSA Size

% Trips by Public Transit

1990 1995

The propensity of American households to travel more was evident regardless of where people

lived (Table 6). However, where people lived did influence how people traveled. Not surprisingly,

people in large metropolitan areas used public transit more often than those in medium and small

areas. Nonetheless, the proportion of trips taken by public transportation decreased across all areas

since 1990.

Figure 2

Percent Trips by Public Transportation per Household by MSA Size

Adjusted 1990 and 1995 NPTS

	


 	


	 	




Since the sample excluded households without telephones, care should be taken in interpreting

results of characteristics that are known to be related to telephone ownership, such as family income

and age. For example, estimates of survey data grouped by family income could underestimate the

impact of low-income households and, therefore, not adequately represent the population as a

whole. Although average household travel increased about three percent per year between 1990

and 1995, this trend did not hold for every household. Only households with income between

$10,000 and $50,000 had this increase, while travel for households at either end of the income

spectrum increased at a more moderate rate, around one percent per year. Low income households

showed a lower growth rate presumably because of budgetary constraints. On the other hand, more

affluent households may have reached a saturation point in travel.

Table 7

Person Trips per Household by Household Income

1983, 1990, and 1995 NPTS

Annual

Income 1983 1990 1990 1995 Compounded Rate

Adjusted 1990-1995

ALL 2,628 2,673 3,262 3,828 3.3%

< $10,000 1,479 1,717 2,106 2,231 1.2%

$10 to $20,000 2,019 2,079 2,548 2,976 3.2%

$20 to $30,000 2,522 2,613 3,201 3,727 3.1%

$30 to $40,000 2,936 3,008 3,681 4,176 2.6%

$40 to $50,000 3,251 3,319 4,052 4,670 2.9%

$50 to $60,000 3,465 3,566 4,344 4,583 1.1%

$60 to $70,000 3,584 3,751 4,560 4,902 1.5%

$70 to $80,000 3,630 3,846 4,676 4,765 0.4%

$80,000+ 3,573 3,760 4,592 4,842 1.1%

Unreported 2,090 2,536 3,424 6.2%

Note:

• Incomes for 1983, 1990, and adjusted 1990 have been adjusted to 1995 dollars.

• All tables reporting totals could include some unreported characteristics.

• Note that only the 1990 data have been adjusted to make them more comparable with the 1995 data. Thus, there are limits on

the conclusions that can be drawn in comparing travel with earlier survey years. The adjustments to 1990 data affect only

person trips, vehicle trips, person miles of travel (PMT) and vehicle miles of travel (VMT).


	


 

While the predominance of private vehicle travel continued, the survey also shows the continued

use of public transit for trips to work or school.

Table 8

Total Person Trips by Mode of Transportation and Trip Purpose

Adjusted 1990 and 1995 NPTS

(millions)

 Private Public Transit Other TOTAL

1990 Adj 1995 1990 Adj 1995 1990 Adj 1995 1990 Adj 1995

Total 267,029 327,400 5,460 6,638 31,746 32,424 304,471 378,930

(87.7%) (86.4%) (1.8%) (1.8%) (10.4%) (8.6%) (100%) (100%)

To or From Work 45,856 60,740 1,992 2,328 2,427 2,397 50,314 66,901

(91.1%) (90.8%) (4.0%) (3.5%) (4.8%) (3.6%) (100%) (100%)

Work Related 3,178 8,835 92 123 249 658 3,529 9,860

Business (90.1%) (89.6%) (2.6%) (1.2%) (7.1%) (6.7%) (100%) (100%)

Family and 128,368 156,065 1,318 2,000 8,809 10,524 138,559 173,764

Personal Business (92.6%) (89.8%) (1.0%) (1.2%) (6.4%) (6.1%) (100%) (100%)

School/Church 17,545 22,436 1,076 826 9,735 8,960 28,397 33,355

(61.8%) (67.3%) (3.8%) (2.5%) (34.3%) (26.9%) (100%) (100%)

Social and 70,382 78,809 946 1,350 10,188 9,799 81,575 94,362

Recreational (86.3%) (83.5%) (1.2%) (1.4%) (12.5%) (10.4%) (100%) (100%)

Other 1,629 470 35 11 338 84 2,014 623

(80.9%) (75.4%) (1.7%) (1.8%) (16.8%) (13.5%) (100%) (100%)

Note:

• All tables reporting totals could include some unreported characteristics.

• Standard Errors for 1995 data in Table 8 are presented in Appendix 5.

• Note that only the 1990 data have been adjusted to make them more comparable with the 1995 data. Thus,

there are limits on the conclusions that can be drawn in comparing travel with earlier survey years. The

adjustments to 1990 data affect only person trips, vehicle trips, person miles of travel (PMT) and vehicle miles

of travel (VMT).
	

 	




Both men and women took more trips in 1995 than in 1990. In 1995, men made more trips per

person than women. Nonetheless, women continued to make more trips than men for family and

personal business. Increases for commuting and for work-related business reflected an increase

of 13 million workers from 1990 to 1995 ( Table 1).

Table 9

Person Trips per Person by Trip Purpose and Gender

Adjusted 1990 and 1995 NPTS

Women Men

1990 Adj 1995 1990 Adj 1995

Total 1,401 1,558 1,339 1,579

(100%) (100%) (100%) (100%)

To or From Work 197 229 259 327

(14.1%) (14.7%) (19.3%) (20.7%)

Work Related 11 23 21 60

Business (0.8%) (1.5%) (1.6%) (3.8%)

Family and Personal 693 786 549 648

Business (49.4%) (50.5%) (41.0%) (41.1%)

School/Church 132 141 123 134

(9.4%) (9.1%) (9.2%) (8.5%)

Social and 358 375 377 406

Recreational (25.6%) (24.1%) (28.2%) (25.7%)

Other 9 3 9 2

(0.6%) (0.2%) (0.7%) (0.1%)

Note:

• Note that only the 1990 data have been adjusted to make them more comparable with the 1995 data. Thus,

there are limits on the conclusions that can be drawn in comparing travel with earlier survey years. The

adjustments to 1990 data affect only person trips, vehicle trips, person miles of travel (PMT) and vehicle miles

of travel (VMT).

• All tables reporting totals could include some unreported characteristics.


0

10

20

30

40

50

To or from

work

Work-related Family and

Personal

Civic, Edu.

and Rel.

Social & Rec.

Percent Trip

1990 Women 1990 Men

1995 Women 1995 Men

The most striking gender difference in travel is non-work travel. More than half of women’s travel

is for family and personal business (e.g., groceries shopping, taking children to school or organized

sports). The comparable rate for men is about 40 percent.

Figure 3

Distribution of Person Trips per Person by Gender and Trip Purpose

Adjusted 1990 and 1995 NPTS

	


 


 	




There is a continuing trend for the typical American household to make more trips per day. On

average, a person five years or older took more than four trips a day, which represents a 14 percent

increase in the past five years (Table 10). Almost one-half of these trips were for family and personal

business. Consistent with the trend on trip frequency, total daily miles of travel also increased.

About one-third of these miles were private vehicle trips for family and personal business (Table 11).

The amount of travel increased for all trip purposes.

Table 10

Daily Trip Rates per Person by Trip Purpose

1977, 1983, 1990, and 1995 NPTS

   	

 

 	
 
 


  	 
	 

 


    


 !
 
     

"#$%$
#$  &   

"# '
#
      

($
  &   

 	   
 


   	
 
 
	


  & &&


 !
 
  &   

"#$%$
#$   & & 

"# '
#
      

($
  & & & 

Note:

• All tables reporting totals could include some unreported characteristics.

• “Other” trip purpose includes trips for work-related business.

• Note that only the 1990 data have been adjusted to make them more comparable with the 1995 data. Thus,

there are limits on the conclusions that can be drawn in comparing travel with earlier survey years. The

adjustments to 1990 data affect only person trips, vehicle trips, person miles of travel (PMT) and vehicle miles

of travel (VMT).
In 1995, an individual traveled on average almost four miles more per day than in 1990. Significant

increases in daily travel for work and for family and personal business were offset somewhat by

a decrease in miles traveled for social and recreational purposes.

Table 11

Distribution of Daily Person Miles of Travel per Person

by Mode of Transportation and Trip Purpose

Adjusted 1990 and 1995 NPTS

Private Public Transit Other TOTAL

Adjusted 1995 Adjusted 1995 Adjusted 1995 Adjusted 1995

 1990 1990 1990 1990

 TOTAL 30.85 35.26 0.74 0.82 3.31 2.20 34.91 38.67

(88.4%) (92.1%) (2.1%) (2.1%) (9.5%) (5.7%) (100%) (100%)

 To or From Work 6.15 8.09 0.27 0.30 0.06 0.22 6.49 8.69

(17.6%) (20.9%) (0.8%) (0.8%) (0.2%) (0.6%) (18.6%) (22.5%)

 Work Related 0.63 1.85 0.01 0.02 0.56 0.34 1.20 2.23

 Business (1.8%) (4.8%) (0.0%) (0.1%) (1.6%) (0.9%) (3.4%) (5.8%)

 Family/Personal 11.39 12.70 0.14 0.19 0.57 0.49 12.10 13.51

 Business (32.6%) (32.8%) (0.4%) (0.5%) (1.6%) (1.3%) (34.7%) (34.9%)

 School/Church 1.32 1.68 0.12 0.07 0.40 0.44 1.84 2.21

(3.8%) (4.3%) (0.3%) (0.2%) (1.1%) (1.1%) (5.3%) (5.7%)

 Social and 11.12 10.83 0.18 0.24 1.71 0.66 13.02 11.86

 Recreational (31.9%) (28.0%) (0.5%) (0.6%) (4.9%) (1.7%) (37.3%) (30.7%)

 Other 0.23 0.10 0.01 0.00 0.01 0.05 0.25 0.15

(0.7%) (0.3%) (0.0%) (0.0%) (0.0%) (0.1%) (0.7%) (0.4%)

Note:

• All tables reporting totals could include some unreported characteristics.

• Note that only the 1990 data have been adjusted to make them more comparable with the 1995 data. Thus,

there are limits on the conclusions that can be drawn in comparing travel with earlier survey years. The

adjustments to 1990 data affect only person trips, vehicle trips, person miles of travel (PMT) and vehicle miles

of travel (VMT).

• Numbers in parenthesis are a percentage of total daily person miles of travel.

	


 
 	




Table 12

Average Daily Person Trips per Person by Age and Gender

1983, 1990, and 1995 NPTS

 TOTAL Men Women

Age 1983 1990 1990 1995 1983 1990 1990 1995 1983 1990 1990 1995

Adj Adj Adj

Total 2.9 3.1 3.8 4.3 2.9 3.0 3.7 4.3 2.9 3.1 3.8 4.3

Under 16 2.3 2.6 3.1 3.7 2.3 2.6 3.0 3.7 2.3 2.6 3.1 3.8

16 to 20 3.3 3.5 4.2 4.6 3.2 3.5 4.2 4.6 3.4 3.5 4.2 4.7

21 to 35 3.5 3.6 4.4 4.6 3.4 3.5 4.2 4.5 3.5 3.7 4.6 4.8

36 to 65 2.9 3.2 3.9 4.6 2.9 3.1 3.7 4.6 3.0 3.3 4.1 4.6

Over 65 1.8 1.9 2.4 3.4 2.2 2.2 2.8 3.9 1.5 1.7 2.2 3.0

Note:

• All tables reporting totals could include some unreported characteristics.

• Note that only the 1990 data have been adjusted to make them more comparable with the 1995 data. Thus,

there are limits on the conclusions that can be drawn in comparing travel with earlier survey years. The

adjustments to 1990 data affect only person trips, vehicle trips, person miles of travel (PMT) and vehicle miles

of travel (VMT).


7.1

24.3

39.3

16.2

11.9

22.6

12.2

36.4

4.3

13.2

23.3

9.5

0

5

10

15

20

25

30

35

40

Under 16 16 to 20 21 to 35 36 to 65 Over 65 Total

Age

Percent Change

Women Men

As a group, both men and women increased their travel from five years ago and, by 1995, took

about an equal number of trips per day (Table 12). Interestingly, different age groups

demonstrated different levels of travel increase. These age-dependent changes were also genderdependent. For example, while males between the ages of 36 and 64 increased their travel by

24 percent during the past five years, their female counterparts only increased their travel by 12

percent. The most striking observation is the travel increases by individuals over 65 years of age.

Regardless of gender, an average elderly person increased her/his travel by almost 40 percent

from 1990.

Figure 4

Percent Change per Person in Personal Travel by Age and Gender

From Adjusted 1990 to 1995

	


 


 	




On average, an individual travels 39 miles per day (Table 11), which represents an increase of 4

miles per day since 1990. These data point to the fact that we probably have not reached a saturation

point in travel. But, as evident in Table 13, there is a great difference between the travel of men

and women. The difference in miles traveled is particularly telling given the fact that men and

women take about an equal number of trips per day. Obviously women’s trips are notably shorter

than men’s trips. Again, the greatest increases in miles traveled per person are by both men and

women over 65 years of age.

Table 13

Average Daily Person Miles of Travel per Person by Age and Gender

1983, 1990, and 1995 NPTS

 Age TOTAL Men Women

1983 1990 1990 1995 1983 1990 1990 1995 1983 1990 1990 1995

Adj Adj Adj

Total 25.1 28.6 34.9 38.7 27.7 31.6 38.0 43.9 22.6 25.8 32.1 33.8

Under 16 16.2 16.2 20.1 25.0 16.8 16.3 20.3 23.7 15.4 16.1 19.9 26.2

16 to 20 22.2 28.1 34.4 36.4 23.0 30.1 36.9 37.6 21.5 26.2 32.2 35.0

21 to 35 31.1 36.5 44.3 46.0 32.8 40.4 48.2 51.3 29.5 32.9 40.7 40.8

36 to 65 29.2 33.0 40.1 45.1 33.6 36.5 43.4 53.2 25.2 29.7 37.0 37.5

Over 65 12.0 14.2 18.4 24.4 14.8 17.4 22.5 31.7 10.2 11.8 15.3 19.2

Note:

• All tables reporting totals could include some unreported characteristics.

• Note that only the 1990 data have been adjusted to make them more comparable with the 1995 data. Thus,

there are limits on the conclusions that can be drawn in comparing travel with earlier survey years. The

adjustments to 1990 data affect only person trips, vehicle trips, person miles of travel (PMT) and vehicle miles

of travel (VMT).


0

10

20

30

40

50

60

Under 16 16 - 20 21 - 35 36 - 65 Over 65

Age

Daily Person Miles of Travel

1990 Women 1990 Men

1995 Women 1995 Men

Figure 5

Average Daily Person Miles of Travel per Person by Gender

Adjusted 1990 and 1995

	


 


In the 1990 NPTS Summary of Travel Trends report, average time spent driving a private vehicle

excluded any drivers who did not drive on the designated travel day. In the 1995 report, average

time spent driving a private vehicle was calculated using two different methods: (1) by including

all drivers, even those who did not drive a private vehicle on the designated travel day, and (2) by

excluding any drivers who did not drive on the designated travel day. Note the 1990 data reported

here are different from those published in the 1990 Nationwide Personal Transportation Survey

Databook, Volume II (Tables 5-66 to 5-68), due to the fact that the 1990 adjusted data are used.

In 1995, a driver spent on average about one hour behind a wheel, an increase of seven minutes

from 1990. People living in smaller cities generally spent slightly less time driving than those living

in large areas.

Table 14

Average Time Spent Driving a Private Vehicle in a Typical Day by MSA Size

Adjusted 1990 and 1995 NPTS

 (in Minutes)

All Drivers Only Persons Who Drove

on Their Travel Day

MSA Size 1990 Adj 1995 1990 Adj 1995

ALL 49.35 56.20 71.88 73.07

Not in MSA 48.85 56.36 69.20 69.14

< 250,000 48.36 53.86 67.94 71.49

250,000 to 499,999 47.82 55.81 71.66 73.12

500,000 to 999,999 50.20 56.76 72.42 72.13

1 to 2.9 million 50.61 56.48 74.38 74.86

3+ million 49.38 56.43 71.08 72.75

Note:

• Average time spent driving does not include any driving done in a segmented trip (see Appendix 6 for the

definition of a segmented trip). Also excludes driving done as an “essential part of work.”

• Note that only the 1990 data have been adjusted to make them more comparable with the 1995 data. Thus,

there are limits on the conclusions that can be drawn in comparing travel with earlier survey years. The

adjustments to 1990 data affect only person trips, vehicle trips, person miles of travel (PMT) and vehicle miles

of travel (VMT).

 	





	


 

The average vehicle occupancy, measured as person miles per vehicle mile, has decreased

consistently over time. This trend is related to the increase in vehicle ownership, and decreases in

household size.

Table 15

Average Vehicle Occupancy for Selected Trip Purposes

1977, 1983, 1990, and 1995 NPTS

(person miles per vehicle mile)

Percent Change

1977 1983 1990 1995 (77-95)

Trip Purpose Total Change

To or From Work 1.3 1.29 1.14 1.14 -15.38%

Shopping 2.1 1.79 1.71 1.74 -19.05%

Other Family or 2.0 1.81 1.84 1.78 -10.00%

Personal Business

Social and Recreational 2.4 2.12 2.08 2.04 -16.67%

All Purposes 1.9 1.75 1.64 1.59 -15.79%

Note:

• All Purposes includes other trip purposes not shown, such as trips to school, church, doctor, dentist, and

work-related business trips.

• Standard Errors for 1995 data in Table 15 are presented in Appendix 5.

• All tables reporting totals could include some unreported characteristics.
	

 !
"# 	




The number and percentage of households without a vehicle continue to decrease over time.

However, there is still concern about the mobility of households without vehicles. The next few

tables will focus on this group. The norm in the United States is that each household is a multi-vehicle

household, with nearly 60 percent of all households having two or more vehicles in 1995.

Table 16

Availability of Household Vehicles

1969, 1977, 1983, 1990, and 1995 NPTS

(thousands)

Households with -- 1969 1977 1983 1990 1995

No Vehicle 12,876 11,538 11,548 8,573 7,989

(20.6%) (15.3%) (13.5%) (9.2%) (8.1%)

One Vehicle 30,252 26,092 28,780 30,654 32,064

(48.4%) (34.6%) (33.7%) (32.8%) (32.4%)

Two Vehicles 16,501 25,942 28,632 35,872 40,024

(26.4%) (34.4%) (33.5%) (38.4%) (40.4%)

Three or More Vehicles 2,875 11,840 16,411 18,248 18,914

(4.6%) (15.7%) (19.2%) (19.6%) (19.1%)

ALL 62,504 75,412 85,371 93,347 98,990

(100.0%) (100.0%) (100.0%) (100.0%) (100.0%)

Vehicles Per Household 1.16 1.59 1.68 1.77 1.78

Note:

• Standard Errors for 1995 data in Table 16 are presented in Appendix 5.

• The 1969 survey does not include pickups or other light trucks as household vehicles.



0

10

20

30

40

50

60

70

No Vehicle Vehicles < Drivers Vehicles = Drivers Vehicles > Drivers

Vehicle to Driver Ratio

Percent Household

< $ 25,000 $25,000 - $54,999

> $55,000

Eighty percent of households in 1995 had at least one vehicle for each of their drivers, representing

a slight decrease from 1990. Most American households continue to have one vehicle for each

of its drivers. It is clear that income affects vehicle ownership and availability. While about onefifth of low income households do not own a vehicle, the comparable percentage in higher income

households is merely one percent.

Figure 6

Household Distribution by Household Income and Vehicle to Driver Ratio

1995 NPTS

	


  !
"#


 !
"# 	




The geographic dispersion of households without a vehicle becomes polarized from the

perspective of population density. Almost one-third of households in areas with a population

density more than 10,000 per square mile do not own a vehicle. On the other hand, almost

70 percent of households in the least densely populated areas own more than two vehicles. The

percent households in these areas without a vehicle declined by almost 40 percent from 1990 to

1995.

Table 17

Distribution of Households by Household Vehicle Availability and Population Density

1990 and 1995 NPTS

 Household Population Density (Persons per Square Mile)

Vehicle

Availability Less than 2,000 2,000 to 4,000 4,000 to 10,000 10,000 or more

1990 1995 1990 1995 1990 1995 1990 1995

ALL 100% 100% 100% 100% 100% 100% 100% 100%

No Vehicle 6.1% 3.9% 7.6% 6.2% 10.9% 8.5% 35.1% 31.0%

One Vehicle 30.4% 27.3% 33.4% 33.8% 38.2% 38.6% 40.0% 41.7%

Two Vehicles 41.0% 44.5% 41.5% 42.3% 34.9% 38.6% 18.4% 21.3%

Three or More 22.5% 24.3% 17.5% 17.7% 16.0% 14.4% 6.5% 6.0%

Vehicles

Note:

• Population Density for 1990 is based on household zipcode areas, whereas 1995 is based on census tract.


Household Distribution by Vehicle Availability

0

10

20

30

40

50

60

70

< 2,000 per sq.

mile

2,000-4,000 per

sq mile

4,000-10,000

per sq. mile

> 10,000 per sq.

mile

Percent Household

No Vehicle One Vehicle Multi-Vehicle

Demographics

50,031

16,852 21,144 10,040

50,011

40,614 23,404

125,706

99,624

30,026 34,596

10,445

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

< 2,000 per sq.

mile

2,000-4,000 per

sq mile

4,000-10,000 per

sq. mile

> 10,000 per sq.

mile

(in thousands)

Households Persons Vehicles

Figure 7

Vehicle Ownership and Demographic Statistics by Population Density

1995 NPTS

	


  !
"#


 !
"# 	




The percent households not owning a vehicle increased with increasing area size. In 1995,

households without a vehicle can be grouped into three broad categories depending on population.

About 5 percent of households are without a vehicle in non-MSA areas or in small cities (<

250,000), whereas more than 10 percent of households in areas with more than 3 million people are

without a vehicle. In large cities, such as New York, some zero-vehicle households are by choice

due to the high cost and the inconvenience of owning a vehicle, and the availability of other modes.

About six to seven percent of the households in medium size cities (with 250,000 to 3 million

people) do not have a vehicle.

Table 18

Percent of Households Without a Vehicle Within MSA Size Group

1977, 1983, 1990 and 1995 NPTS

 % Households Within An Area Without a Vehicle

MSA Size 1977 1983 1990 1995 % Change

1977-1995

Not in (S)MSA 12.2 10.5 7.7 5.3 -57%

< 250,000 13.7 10.1 8.6 4.8 -65%

250,000 to 499,999 12.2 8.1 5.7 7.3 -40%

500,000 to 999,999 14.0 14.3 8.4 6.3 -55%

1 to 2.9 million 14.2 12.1 8.2 6.9 -51%

3+ million 26.1 25.4 12.4 11.2 -57%

ALL 15.3 13.5 9.2 8.1 -47%

Note:

• The population size groups for 1977 - 1983 NPTS are SMSA Size Groups and 1990 - 1995 are MSA Size

Groups (see Appendix 4).

• All tables reporting totals could include some unreported characteristics.


	


  !
"#

Automobiles continue to lose their market share of private vehicles, from 80 percent in 1977 to 65

percent in 1995. In the meantime, minivans and sport utility vehicles (SUVs) claimed a larger

market share. Regardless of vehicle type, all vehicles were in operation longer in 1995 than in the

past.

Table 19

Vehicle Distribution and Average Vehicle Age by Vehicle Type

1977, 1983, 1990, and 1995 NPTS

1977 1983 1990 1995

Distribution of Vehicles

 TOTAL 100.0 100.0 100.0 100.0

 Auto 79.6 75.9 74.7 64.3

 Van 2.8 3.6 5.5 7.8

 Sport Utility NA NA NA 6.9

 Pickup 12.8 15.2 17.2 17.7

 Other Truck 1.3 1.5 0.6 0.4

 RV/Motor Home 0.4 0.5 0.5 0.5

 Motorcycle 2.7 2.5 1.3 0.9

 Moped 0.2 0.6 0.1 NA

 Other 0.2 0.2 0.1 0.1

Average Vehicle Age

 TOTAL 6.6 7.60 7.71 8.33

 Auto 6.4 7.20 7.61 8.24

 Van 5.5 8.45 5.88 6.68

 Sport Utility NA NA NA 6.56

 Pickup 7.3 8.54 8.43 9.65

 Other Truck 11.6 12.39 14.48 14.93

 RV/Motor Home 4.5 10.69 10.44 13.21

Note:

• The 1977, 1983, and 1990 surveys do not include a separate category for sports utility vehicles, while the

1995 survey does. In 1990 survey, most SUVs were classified as automobiles. The 1995 survey does not

include a separate category for mopeds.

• Motorcycle, moped, and other pov are excluded from the calculation of vehicle age.

• All tables reporting totals could include some unreported characteristics.

• Standard Errors for 1995 data in Table 19 are presented in Appendix 5.


 !
"# 	




In 1995, household vehicles remained in operation significantly longer than those in 1969.

This observation is confirmed by both the average vehicle age and by vehicle age

distribution. The 1969 automobiles averaged 5.1 years of age while the 1995 automobiles

average 8.2 years of age—a 3-year or 60 percent increase. In 1995, one-third of vehicles

were at least ten years or older compared to only six percent in 1969. In the past, trucks and

vans tended to be in operation longer than their automobile counterparts. However, this

was no longer true by 1995.

Table 20

Distribution of Vehicles by Vehicle Age and Vehicle Type

1969, 1977, 1983, 1990, and 1995 NPTS

(percentage)

1969 1977 1983 1990 1995

 Vehicle Auto Auto Truck/ All Auto Truck/ All Auto Truck/ All Auto Truck/ All

 Age Van Van Van Van

 0 to 2

 years 41.8 27.3 29.9 27.8 20.0 16.6 19.2 15.6 19.7 16.6 14.9 19.2 16.2

 3 to 5

 years 31.9 30.4 25.6 29.6 28.0 26.6 27.6 27.7 27.2 27.5 21.7 21.6 21.5

 6 to 9

 years 20.1 26.7 21.1 25.7 27.4 25.0 26.9 26.8 20.9 25.3 30.3 25.5 28.5

 10 or more

 years 6.2 15.6 23.4 16.9 24.6 31.8 26.3 29.9 32.2 30.6 33.1 33.7 33.8

 Total 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0

 Average

 Age 5.1 5.5 6.4 5.6 6.7 7.8 6.9 7.6 8.0 7.7 8.2 8.3 8.3

Note:

• The 1969 survey does not include pickups and other light trucks as household vehicles.

• Totals do not include any unreported vehicle ages, but do include vehicle types such as motorcycle, RV, etc.

that are not shown.


Automobiles

0

20

40

60

80

100

69 77 83 90 95

Year

Percent

0-2 years 3-5 years

6-9 years 10 or more years

Trucks and Vans

0

20

40

60

80

100

77 83 90 95

Year

Percent

Figure 8

Distribution of Vehicles by Vehicle Age

1969, 1977, 1983, 1990 and 1995 NPTS

	


  !
"#


 !
"# 	




Based on the owner’s estimates, an average vehicle was driven 12,000 miles a year, similar to the

1990 level. There were not only more old vehicles in 1995 than in the past, they were also driven

more. Although vehicles are becoming “cleaner” due to more stringent emissions standards, the

environmental benefits could be somewhat delayed because of the continued use of older vehicles

and increased use of almost all vehicles.

Table 21

Average Annual Miles per Vehicle by Vehicle Age

(Vehicle Owner’s Estimate)

1969, 1977, 1983, 1990, and 1995 NPTS

Percent Change

Compounded Total

Annual Rate Change

 Vehicle Age 1969 1977 1983 1990 1995 69-95 69-95

 0 to 2 years 15,700 14,460 15,292 16,811 16,092 0.09% 2.50%

 3 to 5 years 11,200 11,074 11,902 13,706 14,004 0.86% 25.04%

 6 to 9 years 9,700 9,199 9,253 12,554 12,608 1.01% 29.98%

 10 or more years 6,500 6,755 7,023 9,176 8,758 1.15% 34.74%

 ALL 11,600 10,679 10,315 12,458 12,226 0.20% 5.39%

Note:

• The 1969 survey does not include pickups and other light trucks as household vehicles.

• All tables reporting totals could include some unreported characteristics.

• Standard Errors for 1995 data in Table 21 are presented in Appendix 5.


0.4

0.6

0.8

1

1.2

1.4

1.6

0-2 years 3 - 5 years 6 - 9 years 10 or more years

Vehicle Age

Annual Miles Indexed

to Avg. Miles 

1969 1977 1983

1990 1995

There is a trend of older vehicles being driven more than before. In 1969, a 3-5 year old vehicle

was driven, on average, the same number of miles as the average for all vehicles. In 1995, this

pattern had changed to 6-9 year old vehicles (note that the graphs in Figure 9 shift to the right). Also,

consistent with this pattern, vehicles ten or more years old are being driven more, relative to the

average among all vehicles.

Figure 9

Annual Miles Driven Per Vehicle, Indexed to the Annual Average

1969, 1977, 1983, 1990 and 1995 NPTS

	


  !
"#
	

 !
"# 	




Based on 1990 and 1995 NPTS data, the overall estimate of annual miles driven per licensed driver

increased. In 1995, elderly men drove on average 1,000 miles more than those in 1990. However,

this increase in driving was not true for all age groups. Teenage drivers reduced their driving from

the 1990 level. However, the differences in teen driving between 1990 and 1995 are not statistically

significant.

Table 22

Average Annual Miles per Licensed Driver by Driver Age and Gender

(Self Estimate)

1969, 1977, 1983, 1990, and 1995 NPTS

 Percent Change

 Driver Age 1969 1977 1983 1990 1995 Annual Rate Total Change

69-95 69-95

ALL

 16 to 19 4,633 5,662 4,986 8,485 7,624 1.93% 64.56%

 20 to 34 9,348 11,063 11,531 14,776 15,098 1.86% 61.51%

 35 to 54 9,771 11,539 12,627 14,836 15,291 1.74% 56.49%

 55 to 64 8,611 9,196 9,611 11,436 11,972 1.28% 39.03%

 65+ 5,171 5,475 5,386 7,084 7,646 1.52% 47.86%

 ALL 8,685 10,006 10,536 13,125 13,476 1.70% 55.16%

Men

 16 to 19 5,461 7,045 5,908 9,543 8,206 1.58% 50.27%

 20 to 34 13,133 15,222 15,844 18,310 17,976 1.21% 36.88%

 35 to 54 12,841 16,097 17,808 18,871 18,858 1.49% 46.86%

 55 to 64 10,696 12,455 13,431 15,224 15,859 1.53% 48.27%

 65+ 5,919 6,795 7,198 9,162 10,304 2.16% 74.08%

 ALL 11,352 13,397 13,962 16,536 16,550 1.46% 45.79%

Women

 16 to 19 3,586 4,036 3,874 7,387 6,873 2.53% 91.66%

 20 to 34 5,512 6,571 7,121 11,174 12,004 3.04% 117.78%

 35 to 54 6,003 6,534 7,347 10,539 11,464 2.52% 90.97%

 55 to 64 5,375 5,097 5,432 7,211 7,780 1.43% 44.74%

 65+ 3,664 3,572 3,308 4,750 4,785 1.03% 30.59%

 ALL 5,411 5,940 6,382 9,528 10,142 2.45% 87.43%

Note:

• All tables reporting totals could include some unreported characteristics.

• In 1995, some drivers indicating that they drove ‘no miles’ for their average annual miles were changed to

‘miles not reported.’ (See Appendix 7 for details on data revision.)

• Standard Errors for 1995 data in Table 22 are presented in Appendix 5.



Table 23

Commute VMT and Total VMT By Year

1969, 1977, 1983, 1990, and 1995 NPTS


  	  $ 

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Note:

• Caution should be used when comparing the number of workers or the number of commute trips between the

1990 and 1995 NPTS. Slightly different approaches were used in defining workers and commute trips between

the 1990 and 1995 NPTS (see Appendix 3).

	


 $

	


79.6%

11.1%

0.3%

5.1%

3.9%

Auto, Truck, Van , or U.V. - Usually Drive Alone

Auto, Truck, Van , or U.V. - Usually Carpool

Auto, Truck, Van , or U.V. - Carpool Status Unknown

Public Transit 

Other

$

	 	




Figure 10

Distribution of Workers by Usual Mode

1995 NPTS

(percentage)


Workers in the United States predominately traveled to work in privately-owned vehicles. About

five percent of the commuters reported public transit as their usual mode to work, which represents

the same level as in 1990.

Table 24

Distribution of Workers by Usual Mode

1969, 1977, 1983, 1990, and 1995 NPTS

(percentage)

 Mode of Transportation 1969 1977 1983 1990 1995

 All Modes 100.0 100.0 100.0 100.0 100.0

 Auto, Truck, Van, or Utility Vehicle 90.8 93.0 92.4 87.8 91.0

 Public Transit 8.4 4.7 5.8 5.3 5.1

 Other 0.8 2.3 1.8 6.9 3.9

Note:

• Usual mode is defined as the means of transportation usually used to go to work during the week before the

interview. Data in this table are derived from the person file.

• The 1969 survey excludes walk trips.

• All modes does not include workers who worked at home or any unreported modes.

• Other includes other modes not shown above such as RV, motorcycle, other POV, Amtrak, airplane, taxi, bike,

walk, school bus, and other.

• Standard Errors for 1995 data in Table 24 are presented in Appendix 5.

	


 $

	


$

	 	




The average commute was one mile longer in 1995 than in 1990. However, with somewhat

improved commute speeds, the average commute time increased only slightly. Although having

only slightly longer commute distances, those who used public transit spent twice as long on their

commute as those who drove or rode in privately-owned vehicles (Figure 11).

Table 25

General Commute Patterns by Mode of Transportation

1983, 1990, and 1995 NPTS

1983 1990 1995 1983 1990 1995 1983 1990 1995 1983 1990 1995

 ALL MODES Private Public Transit Other

Average Commute Trip Length (miles)

8.54 10.65 11.63 8.86 11.02 11.84 11.81 12.75 12.88 1.35 2.15 8.15

Average Commute Travel Time (minutes)

18.20 19.60 20.65 17.62 19.05 20.10 39.77 41.10 41.95 10.58 12.41 18.82

Average Commute Speed (miles per hour)

28.17 33.33 33.80 30.18 34.74 35.36 17.82 18.23 19.29 7.63 7.61 25.89

Note:

• All trip miles and travel times were calculated using actual trips to and from work as reported in the travel day

file.

• Average commute trip length for 1990 and 1995 is calculated using only those records with trip mileage

information present.

• Average commute travel time does not include time spent waiting for transportation.

• Average commute speed for 1990 and 1995 NPTS does not include any segmented trips because a change in

the mode of transportation during the trip would cause the calculation of average commute speed to be

meaningless. (see Appendix 6 for the definition of a segmented trip).

• All tables reporting totals could include some unreported characteristics.


49.6

43.9

19.0

42.2

19.4

35.2

23.5

42.6

17.4

17.0

37.2

17.6

0.0

10.0

20.0

30.0

40.0

50.0

Private Vehicle Public Transit

MSA Size

Average Commute Time (in min.) 

Not in MSA < 250,000

250,000-499,999 500,000-999,999

1 to 2.9 million > 3 million

Figure 11

Average Travel Time for Commuting by Selected Travel Mode and MSA Size

1995 NPTS

	


 $

	


$

	 	




Table 26

Average Commute Speed by MSA Size

1983, 1990, and 1995 NPTS

(miles per hour)

 MSA Size

Not in Less than 250,000 to 500,000 to 1 to 2.9 3 million

MSA 250,000 499,999 999,999 million and over

1983 31.97 27.20 30.09 28.52 28.11 24.32

1990 38.34 32.85 34.22 34.84 31.89 30.99

1995 39.11 35.67 35.72 34.76 34.89 32.29



 	
	
		
	
	
				
			

			
			
		

 
	

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MSA Size

0

5

10

15

20

25

30

35

40

6-9 am 9 am - 1 pm 1-4 pm 4-7 pm Average

Time of Day

Commute Speed

Not in MSA < 250,000

250,000-499,999 500,000-999,999

1 - 2.9 million > 3 Million

Generally, as the population of an area increases, commute speeds decrease. Depending on the time

of day and location, average commute speeds ranged from 29 to 47 miles per hour in 1995. In

almost all areas, commute speeds improved from 1983. In larger areas, the lowest speeds tended

to occur in the late afternoon and early evening, while in areas with less than 250,000 people the

lowest speeds occurred between 9 am and 1 pm.

Figure 12

Average Commute Speed for Selected Time of Day by MSA Size

1995 NPTS

(miles per hour)

	


 $

	



!	 	




The temporal distribution of personal trips remained the same during the past decade—more than

two-fifths of the trips started between 9 o’clock in the morning and 4 o’clock in the afternoon.

However, this distribution varies somewhat by trip purpose (see Figure 13). As expected,

commuting to and from work began predominately between 6 and 9 o’clock in the morning and

between 4 and 7 o’clock in the afternoon while more than half of work-related trips started between

9 am and 4 pm.

Table 27

Distribution of Person Trips by Start Time of Trip

1983, 1990, and 1995 NPTS

Time of Day 1983 1990 1990 1995

Adj

10 pm - 1 am 4.0 4.0 4.1 3.5

1 - 6 am 3.3 1.9 1.8 1.7

6 - 9 am 14.4 13.9 12.5 13.8

9 am - 1 pm 23.4 20.1 20.6 24.2

1 - 4 pm 20.8 20.4 20.7 22.1

4 - 7 pm 21.2 22.8 22.9 23.0

7 - 10 pm 12.3 12.8 13.2 11.8

ALL 100.0 100.0 100.0 100.0

Note:

• All tables reporting totals could include some unreported characteristics.

• Note that only the 1990 data have been adjusted to make them more comparable with the 1995 data. Thus,

there are limits on the conclusions that can be drawn in comparing travel with earlier survey years. The

adjustments to 1990 data affect only person trips, vehicle trips, person miles of travel (PMT) and vehicle miles

of travel (VMT).


0

5

10

15

20

Midnight 1

2

3

4

5

6

7

8

9

10

11

12 1

2

3

4

5

6

7

8

9

10

11

Start Time of Trip

Percent Trip

Commute Work-Related Fam & Personal

School/Church Soc & Rec

	


 
!	

Figure 13

Distribution of Person Trips by Trip Purpose and Start Time of Trip

1995 NPTS
	


!	 	




Although travel was less frequent on weekends than on weekdays, weekend trips were on average

longer than weekday trips. This is true for both 1990 and 1995. In 1995, the average daily time

spent driving was ten minutes longer on weekdays than on weekends.

Table 28

Daily Travel Statistics by Weekday vs Weekend

Adjusted 1990 and 1995 NPTS

Daily Travel Statistics 1990 Adjusted 1995

Weekday Weekend Weekday Weekend

Vehicle Trips per Driver 3.41 2.89 3.81 2.99

% work trips 27.8% 9.7% 31.9% 12.5%

% non-work trips 72.2% 90.3% 68.1% 87.5%

VMT per Driver 28.54 28.36 33.46 28.87

Average Vehicle Trip Length 8.47 9.96 8.85 9.73

Average Time Spent Driving (in minutes) 50.68 46.07 59.48 48.05

Person Trips per Person 3.82 3.60 4.43 3.96

PMT per Person 32.6 40.64 37.68 41.14

Average Person Trip Length 9.47 11.51 8.63 10.53

Note:

• Average time spent driving includes all drivers, even those who did not drive a private vehicle on the day in

which the household was interviewed. It does not include any driving done in a segmented trip (see Appendix 6

for the definition of a segmented trip). Also excludes driving done as an “essential part of work.”

• Average trip length is calculated using only those records with trip mileage information present.

• Standard Errors for 1995 data in Table 28 are presented in Appendix 5.

• Note that only the 1990 data have been adjusted to make them more comparable with the 1995 data. Thus, there

are limits on the conclusions that can be drawn in comparing travel with earlier survey years. The adjustments to

1990 data affect only person trips, vehicle trips, person miles of travel (PMT) and vehicle miles of travel (VMT).



Travel statistics indicated that the population 65 and older was more mobile in 1995 than its

corresponding cohort in 1990. On a daily basis, older drivers drove an average of 32 percent more

miles, took 38 percent more trips, and spent 12 more minutes driving daily in 1995 than in 1990.

Table 29

Daily Travel Statistics of People 65 and Older

1983, 1990, and 1995 NPTS

Daily Travel Statistics 1983 1990 1990 1995

Adjusted

Vehicle Trips per Driver 1.66 1.78 2.27 2.94

% work trips 10.2% 6.2% 4.8% 8.5%

% non-work trips 89.8% 93.8% 95.2% 91.5%

VMT per Driver 9.80 11.50 14.83 19.56

Average Vehicle Trip Length 5.92 6.55 6.61 6.69

Average Time Spent Driving (in minutes) na 24.02 30.83 42.89

Person Trips per Person 1.82 1.95 2.49 3.43

PMT per Person 12.21 15.33 19.85 25.24

Average Person Trip Length 6.70 7.99 8.12 7.46

Note:

• Average time spent driving includes all drivers, even those who did not drive a private vehicle on the day in

which the household was interviewed. It does not include any driving done in a segmented trip (see Appendix 6

for the definition of a segmented trip). Also excludes driving done as an “essential part of work.”

• Average trip length is calculated using only those records with trip mileage information present.

• Note that only the 1990 data have been adjusted to make them more comparable with the 1995 data. Thus,

there are limits on the conclusions that can be drawn in comparing travel with earlier survey years. The

adjustments to 1990 data affect only person trips, vehicle trips, person miles of travel (PMT) and vehicle miles

of travel (VMT).

	


 %	!&	


%	!&	 	




Regardless of household composition, women took more trips in 1995 than in 1990. Women with

children between the ages 6 and 15, whether a single parent or in a 2-adult household, averaged

more than 5 trips per day. The proportion of the trips women took to and from work increased from

1990 to 1995.

Table 30

Daily Person Trips of Adult Women by Household Composition

1983, 1990, and 1995 NPTS

1983 1990 Adjusted 1995

 Household Composition 1990

All % work All % work All % work All % work

trips trips trips trips

ALL 2.95 17.56% 3.23 17.65% 4.00 14.25% 4.36 15.83%

Single Adult, No Child 2.60 23.52% 3.32 23.80% 4.07 19.41% 4.19 25.78%

 2 or > Adult, No Child 2.85 25.56% 3.29 25.84% 4.01 21.20% 4.19 25.06%

 Single Adult, Child<6 2.65 11.02% 3.59 12.53% 4.48 10.04% 4.80 12.71%

 2 or > Adult, Child<6 3.32 10.18% 3.51 13.68% 4.41 10.88% 4.74 12.03%

 Single Adult, Child 6-15 3.73 14.12% 4.17 13.43% 5.17 10.83% 5.35 11.59%

 2 or > Adult, Child 6-15 3.59 13.94% 3.85 12.99% 4.78 10.46% 5.24 11.64%

 Single Adult, Child 16-21 2.59 28.80% 3.41 20.53% 4.17 16.79% 4.56 22.37%

 2 or > Adult, Child 16-21 2.84 28.88% 3.40 24.71% 4.13 20.34% 4.54 20.93%

 Single Adult, Retired* 1.49 0.00% 1.79 1.68% 2.30 1.30% 3.06 0.65%

 2 or > Adult, Retired* 1.97 12.76% 2.17 9.68% 2.75 7.64% 3.48 8.33%

Note:

• All tables reporting totals could include some unreported characteristics.

• In 1983, adult women were defined as all females 16 or older. In 1990 and 1995, adult women were defined as

females 18 or older.

• Note that only the 1990 data have been adjusted to make them more comparable with the 1995 data. Thus,

there are limits on the conclusions that can be drawn in comparing travel with earlier survey years. The

adjustments to 1990 data affect only person trips, vehicle trips, person miles of travel (PMT) and vehicle miles

of travel (VMT).

• *Many “retired” people continue to work which is why they report trips to and from work.


	


 %	!&	

Individuals in low income households took, on average, about four trips a day in 1995, continuing

an upward trend. As expected, a smaller portion of trips in low income households were for work

or work-related activities.

Table 31

Daily Person Trips per Person for Low Income Households by Trip Purpose

1983, 1990, and 1995 NPTS

1(%23 4

" +15', 3

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Note:

• Incomes for 1983 and 1990 have been adjusted to 1995 dollars.

• Low income households are defined as a household earning $25,000 or less in a year.

• All tables reporting totals could include some unreported characteristics.

• Note that only the 1990 data have been adjusted to make them more comparable with the 1995 data. Thus,

there are limits on the conclusions that can be drawn in comparing travel with earlier survey years. The

adjustments to 1990 data affect only person trips, vehicle trips, person miles of travel (PMT) and vehicle miles

of travel (VMT).


%	!&	 	




In 1995, people in households without a vehicle averaged 1.3 fewer trips per day than those in

households with vehicles. The impact of owning a vehicle on mobility was the greatest for those

who lived in areas with less than one quarter of a million people.

Table 32

Daily Person Trips per Person

by Vehicle Ownership Status and MSA Size

Adjusted 1990 and 1995 NPTS

 MSA Size 1990 Adjusted 1995

Without Vehicle With Vehicles Without Vehicle With Vehicles

 ALL 2.28 3.86 3.04 4.38

 Not in MSA 1.81 3.80 2.92 4.43

 < 250,000 2.87 4.11 2.43 4.54

 250,000 to 499,999 1.92 3.95 3.17 4.47

 500,000 to 999,999 1.80 3.98 2.69 4.45

 1 to 2.9 million 2.23 3.91 3.00 4.41

 3 million + 2.50 3.72 3.13 4.26

Note:

• Note that only the 1990 data have been adjusted to make them more comparable with the 1995 data. Thus,

there are limits on the conclusions that can be drawn in comparing travel with earlier survey years. The

adjustments to 1990 data affect only person trips, vehicle trips, person miles of travel (PMT) and vehicle miles

of travel (VMT).


Not in MSA

21.0%

50.9%

1.9%

26.2%

Driver of POV Passenger of POV

Public Other

Areas with 250,000 to 1 million people

19.0%

39.0%

8.2%

33.7%

Areas with 1 to 3 million people

13.1%

44.0%

13.8%

29.1%

Areas with 3 million people or more

7.5% 19.5%

28.8%

44.2%

	


 %	!&	

Figure 14 focuses on households without a vehicle. Those without access to a privately-owned

vehicle met many of their transportation needs by riding as a passenger in a privately-owned vehicle,

or by walking or bicycling. Of those who lived in large metropolitan areas with three million or more

people, almost three-quarters of the trips were by walk, bike or public transit.

Figure 14

Mode Distribution of Person Trips Taken by Zero-Vehicle Households

1995 NPTS

Note:

• Other includes other modes not shown above such as RV, motorcycle, other POV, Amtrak, airplane, taxi, bike,

walk, school bus, and other.


REFERENCES

1. PlanTrans, Draft report on NPTS Pretest Methods, Spring 1997

/ 	





TRAVEL CONCEPTS AND

GLOSSARY OF TERMS

	


 



This page intentionally left blank.


 	





TRAVEL CONCEPTS

PERSON TRIP DEFINITION - A trip by one person in any mode of transportation.

This is the most basic and universal measure of personal travel. Each

 record in the Travel Day and Travel Period files in the NPTS data set

represents one person trip.

EXAMPLES - Two people traveling together in one car are counted as

two person trips. Three people walking to the store together are counted

 as three person trips.

PERSON DEFINITION - The number of miles traveled by each person on a trip.

MILES OF

TRAVEL EXAMPLES - If two people traveling together take a six-mile subway

(PMT) trip to the airport, that trip results in 12 person miles of travel. A fourmile van trip with a driver and three passengers counts as 16 person miles

of travel.

VEHICLE DEFINITION - A trip by a single privately operated vehicle (POV)

TRIPS regardless of the number of persons in the vehicle.

EXAMPLES - Two people traveling together in a car would be counted

as one vehicle trip. Four people going to a restaurant in a van is

considered one vehicle trip.

NPTS MODE RESTRICTIONS - To be considered a vehicle trip in

NPTS, the trip must have been made in a privately operated vehicle,

namely a household-based car, van, sport utility vehicle, pickup truck,

other truck, recreational vehicle, motorcycle or other POV. The vehicle

does not need to belong to the household.

Trips made in other highway vehicles, such as buses, streetcars, taxis, and

school buses are collected in the NPTS, but these are shown as person

trips by those modes. The design of the NPTS is such that it does not

serve as a source for vehicle trips in modes such as buses, because there is

no way to trace the movement of the bus fleet throughout the day. Those

interested in vehicle trips by buses, taxis, etc. need to use a data source

	


 



that relies on reports from the fleet operators of those vehicles. The

National Transit database

 (www.fta.dot.gov/ntl/index.html) provided by the Federal Transit

Administration is one such source.

VEHICLE DEFINITION - One vehicle mile of travel is the movement of one

MILES OF privately operated vehicle (POV) for one mile, regardless of the number

TRAVEL of people inthe vehicle.

(VMT)

EXAMPLES- When one person drives her car 12 miles to work, 12

vehicle miles of travel have been made. If two people travel three miles

by pickup, three vehicle miles of travel have been made.

SAME MODE RESTRICTIONS - For NPTS data, vehicle miles are

restricted to the same privately-operated vehicles as vehicle trips (see

above), that is a household-based car, van, sport utility vehicle, pickup

truck, other truck, recreational vehicle, or other POV.

VEHICLE DEFINITION - For NPTS data, vehicle occupancy is generally

OCCUPANCY computed as person miles of travel per vehicle mile (referred to as the

travel method). Note that the other commonly-used definition of vehicle

occupancy is persons per vehicle trip (referred to as the trip method).

COMMENTS - Because longer trips often have higher occupancies, the

travel method generally yields a higher rate (1.59 for the 1995 NPTS)

than the trip method (1.50). The calculation of the travel method requires

that trip miles be reported, thus it is calculated on a slightly smaller

number of trips than the trip method.


 	





GLOSSARY OF TERMS

This glossary provides the most common terms used in the NPTS and

definitions of those terms. These definitions are provided to assist the

user in the interpretation of the NPTS data.

Adult For NPTS, this is defined as a person 18 years or older.

Consolidated A large metropolitan complex of one million or more population,

Metropolitan containing two or more identifiable component parts designated as

Statistical Area primary metropolitan statistical areas (PMSAs). For example, the Boston

(CMSA) CMSA is composed of six PMSAs.

Destination For travel day trips, the destination is the point at which there is a break

in travel, except if the break is only to change vehicles or means of

transport.

For travel period trips, the destination is the farthest point of travel.

Driver A driver is a person who operates a motorized vehicle. If more than one

person drives on a single trip, the person who drives the most miles is

classified as the principal driver.

Employed A person is considered employed if he/she worked for pay, either full time

or part time, during the week before the interview.

Education Level The number of years of regular schooling completed in graded public,

private, or parochial schools, or in colleges, universities, or professional

schools, whether day school or night school. Regular schooling advances

a person toward an elementary or high school diploma, or a college,

university, or professional school degree.

Household A group of persons whose usual place of residence is a specific housing

unit; these persons may or may not be related to each other. The total of

all U.S. households represents the total civilian non-institutionalized

population. A household does not include group quarters (i.e., ten or

more persons living together, none of whom are related).

	


 

	

Household Household income is the money earned by all family members in a

Income household, including those temporarily absent. Annual income consisted

of the income earned 12 months preceding the interview. Household

income includes monies from all sources, such as wages and salary,

commissions, tips, cash bonuses, income from a business or farm,

pensions, dividends, interest, unemployment or workmen’s compensation,

social security, veterans’ payments, rent received from owned property

(minus the operating costs), public assistance payments, regular gifts of

money from friends or relatives not living in the household, alimony, child

support, and other kinds of periodic money income other than earnings.

Household income excludes in-kind income such as room and board,

insurance payments, lump-sum inheritances, occasional gifts of money

from persons not living in the same household, withdrawal of savings

from banks, tax refunds, and the proceeds of the sale of one’s house, car,

or other personal property.

Household Household members include all people, whether present or temporarily

Members absent, whose usual place of residence is in the sample unit. Household

members also include people staying in the sample unit who have no other

usual place of residence elsewhere.

Household A household vehicle is a motorized vehicle that is owned, leased, rented

Vehicle or company-owned and available to be used regularly by household

members during the two-week travel period. Household vehicles include

vehicles used solely for business purposes or business-owned vehicles, so

long as they are driven home and can be used for the home to work trip,

(e.g., taxicabs, police cars, etc.). Household vehicles include all vehicles

that were owned or available for use by members of the household during

the travel period, even though a vehicle may have been sold before the

interview. Vehicles excluded from household vehicles are those which

were not working and were not expected to be working within 60 days,

and vehicles that were purchased or received after the designated travel

day.

Licensed Driver A licensed driver is any person who holds a valid driver’s license from any

state.

Means of A mode of travel used for going from one place (origin) to another

Transportation (destination). A means of transportation includes private and public


 	





modes, as well as walking. For all travel day trips, each change of mode

constitutes a separate trip. The following transportation modes, grouped

by major mode, are included in the NPTS data.

Private Vehicle

Automobile. A privately owned and/or operated licensed motorized

vehicle including cars and station wagons. Leased and rented cars are

included if they are privately operated and not used for picking up

passengers in return for fare.

Van. A privately owned and/or operated van or minivan designed to

carry 5 to 13 passengers, or to haul cargo.

Sport Utility Vehicle. A privately owned and/or operated vehicle

that is a hybrid of design elements from a van, a pickup truck and a

station wagon. Examples include a Chevrolet Blazer, Ford Bronco,

Jeep Cherokee, or Nissan Pathfinder.

Pickup Truck. A pickup truck is a motorized vehicle, privately

owned and/or operated, with an enclosed cab that usually

accommodates two-three passengers, and an open cargo area in the

rear. Pickup trucks usually have the same size of wheel-base as a fullsize station wagon. This category also includes pickups with campers.

Other Truck. This category consists of all trucks other than pickup

trucks (i.e., dump trucks, trailer trucks, etc.).

RV or Motor Home. An RV or motor home includes a self-powered

recreational vehicle that is operated as a unit without being towed by

another vehicle (e.g., a Winnebago motor home).

Motorcycle. This category includes large, medium, and small

motorcycles. Minibikes are excluded because they cannot be licensed

for highway use.

Other POV. A vehicle that cannot be classified into one of the

categories above.

	


 



Public Transportation

Bus. The bus category includes intercity buses, mass transit systems,

and shuttle buses that are available to the general public. Also, DialA-Bus and Senior Citizen buses that are available to the public are

included in this category. However, shuttle buses operated by a

government agency or private industry for the convenience of

employees, contracted or chartered buses, or school buses are

excluded from this category.

Commuter Train. This category includes commuter trains and

passenger trains other than elevated rail trains and subways. Commuter

Train also includes local and commuter train service. Amtrak intercity

service is excluded from this category.

Streetcar/Trolley. This category includes trolleys, street-cars, and

cable cars.

Elevated Rail/Subway. This category includes elevated railways and

subway trains in a city.

Other Modes

Amtrak. Amtrak is defined as the U.S. national passenger railroad

service providing intercity train service. Amtrak intercity service is

excluded from the commuter train data.

Airplane. Airplanes include commercial airplanes and smaller planes

that are available for use by the general public in exchange for a fare.

Private planes and helicopters are included under “Other.”

Taxi. Taxis include the use of a taxicab by a driver for hire, or by a

passenger for fare, and airport limousines. The taxi category does not

include rental cars if they are privately operated and not picking up

passengers in return for fare.

Bicycles. This category includes bicycles of all speeds and sizes that

do not have a motor.

Walk. This category includes walking and jogging.


 	





School Bus. This category includes county school buses, private

school buses, and buses chartered from private companies for the

express purposes of carrying students to or from school and/or schoolrelated activities.

Moped (Motorized Bicycle). This category includes motorized

bicycles equipped with a small engine, typically characteristic of a two

horsepower motor or less. Minibikes, dirt bikes, and trail bikes are

excluded from this category. Note that a motorized bicycle may or

may not be licensed for highway use.

Other. Includes any type of transportation not previously listed, e.g.

ferry boat.

Metropolitan Except in the New England States, a Metropolitan Statistical Area is a

Statistical Area county or group of contiguous counties which contains at least one city

(MSA) of 50,000 inhabitants or more, or “twin cities” with a combined

population of at least 50,000. In addition, contiguous counties are

included in an MSA if, according to certain criteria, they are socially and

economically integrated with the central city. In the New England States,

MSA’s consist of towns and cities instead of counties.

Motorized Motorized vehicles are all vehicles that are licensed for highway driving.

Vehicle Snow mobiles and minibikes are specifically excluded.

Occupancy Occupancy is the number of persons, including driver and passenger(s) in

a vehicle. NPTS occupancy rates are generally calculated as person miles

divided by vehicle miles.

Passenger For a specific trip, a passenger is any occupant of a motorized vehicle,

other than the driver.

Person Miles of PMT is a primary measure of person travel. When one person travels one

Travel (PMT) mile, one person mile of travel results. Where two or more persons travel

together in the same vehicle, each person makes the same number of

	


 



person miles as the vehicle miles. Therefore, 4 persons traveling 5 miles in

the same vehicle results in 20 person miles (4 x 5 = 20).

Person Trip A person trip is a trip by one or more persons in any mode of

transportation. Each person is considered as making one person trip. For

example, four persons traveling together in one auto are counted as four

person trips.

POV A privately-owned vehicle or privately-operated vehicle. Either way, the

intent here is that this is not a vehicle available to the public for a fee,

such as a bus, subway, taxi, etc.

Travel Day A travel day is a 24-hour period from 4:00 a.m. to 3:59 a.m. designated

as the reference period for studying trips and travel by members of a

sampled household.

Travel Day Trip A travel day trip is defined as any time the respondent went from one

address to another by private motor vehicle, public transportation,

bicycle, walking, or other means. However, a separate trip is not counted

in two instances:

1. When the sole purpose for the trip is to get to another vehicle or

mode of transportation in order to continue to the destination.

2. Travel within a shopping center, mall or shopping areas of 4-5

blocks is to be considered as travel to one destination.

Trip Purpose A trip purpose is the main reason that motivates a trip. For purposes of

this report, there are 11 trip reasons. For travel day trips, if there is more

than one reason, and the reasons do not involve different destinations,

then only the main reason is chosen. If there are two or more reasons,

and they each involve different destinations, then each reason is classified

as a separate trip. For travel period trips, if there is more than one

reason, the primary reason is collected. The 11 trip reasons (grouped into

the six major purposes) are defined as follows:

To or From Work Travel between home and a place where one

reports for work.


 	





Work-Related Trips for the respondent’s job or business, other than

to or from the workplace. Examples: a plumber drives to a wholesale

dealer to purchase supplies for his business, or a company executive

travels from his office to another firm to attend a business meeting.

Out-of-town business trips and professional conventions are included

in this category.

FAMILY AND PERSONAL BUSINESS:

Shopping. Shopping includes “window-shopping” and purchases

of commodities such as groceries, furniture, clothing, etc. for use

or consumption elsewhere.

Doctor/Dentist. This category includes trips made for medical,

dental, or psychiatric treatment, or other related professional

services.

Other Family or Personal Business. This category includes the

purchase of services such as cleaning garments, servicing an

automobile, haircuts, banking, legal services, etc.

SCHOOL OR CHURCH:

School/Church. This category includes trips to school, college

or university (for classes), or to PTA meetings, seminars, etc., or

to church services or to participate in other religious activities.

Social activities that take place at a church or school, but cannot

be classified as religious or educational are not included in this

category.

SOCIAL AND RECREATIONAL:

Vacation. This category is for trips reported by the respondent

as “vacation.”

Visit Friends or Relatives. Trips which are specifically

designated to visit friends or relatives.

Pleasure Driving. Driving trips made with no other purpose

listed but to “go for a drive” with no destination in mind.

	


 



Other Social or Recreational. Trips taken to enjoy some form

of social activity involving friends or acquaintances. This category

includes trips for general entertainment or recreation (both as

observer or as participant).

OTHER:

Other. For trips that do not fit in any of the other categories.

Urbanized Area An urbanized area consists of the built up area surrounding a central core

(or central city), with a population density of at least 1,000 persons per

square mile. Urbanized areas do not follow jurisdictional boundaries,

thus it is common for the urbanized area boundary to divide a county.

For the 1995 NPTS, an approximate classification of sample households

was based upon the population density of the Census block group

containing the household. Households in block groups estimated to have

at least 1,000 persons per square mile were classed as urban; those in

block groups with less than 1,000 persons per square miles were classed

as not urban.

Vehicle In the 1995 NPTS, the term vehicle includes autos, passenger vans, sport

utility vehicles, pickups and other light trucks, RV’s, motorcycles and

mopeds owned or available to the household. Note that in the 1969

NPTS, the term vehicle was limited to cars or passenger vans. Estimates

show that in 1969 there were an additional 7.5 million pickups and other

light trucks that are not reflected in the 1969 NPTS data.

Vehicle Miles of VMT is a unit to measure vehicle travel made by a private vehicle, such

Travel (VMT) as an automobile, van, pickup truck, or motorcycle. Each mile traveled is

counted as one vehicle mile regardless of the number of persons in the

vehicle.

Vehicle Vehicle occupancy is the number of persons, including driver and

Occupancy passenger(s) in a vehicle; also includes persons who did not complete a

whole trip. NPTS occupancy rates are generally calculated as person

miles divided by vehicle miles.

Vehicle Trip A trip by a single privately-operated vehicle (POV) regardless of the

number of persons in the vehicle.


 	





Vehicle Type For purposes of the 1995 NPTS, one of the following:

1. Automobile (including station wagon)

2. Van

3. Sport Utility Vehicle

4. Pickup Truck (including pickup with camper)

5. Other Truck

6. RV or Motor Home

7. Motorcycle

8. Other

See “Means of Transportation” for definitions of these vehicle types. For

NPTS, vehicle types are limited to privately operated vehicles (POV)

because other vehicles that the respondent may have rode in (e.g., bus)

were not tracked throughout the day, as was the case with household

vehicles.

Weekday Weekday is defined as the time between 12:01 a.m. Monday and

midnight Friday.

Weekend Weekend is defined as the time between 12:01 a.m. Saturday and

midnight Sunday.

Worker See “Employed”

	


 







 	





APPENDIX 1

CHANGES IN THE 1995 NPTS SURVEY METHODOLOGY

AND THEIR PROBABLE IMPACTS

	


 


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APPENDIX 1

CHANGES IN THE 1995 NPTS SURVEY METHODOLOGY

AND THEIR PROBABLE IMPACTS

 Change From 1990 To 1995 Probable Impacts

 Respondent Contact No advance letters Advance letters Improved response.

Legitimizes the survey with

respondents.

No incentive Incentive ($2/person) Improved respondent

cooperation rates, may have

increased trip reporting.

 Trip Reporting Recall Travel Diary More trips reported,

especially incidental trips

and trips for family &

personal business and social

& recreational purposes.

All trips for individual Household rostering Include trips that may have

person are collected of trips been forgotten. More

independently consistent trip data. Lower

respondent burden. More

coherent picture of household

trip making.

Did not specifically Specifically More accurate count of

confirm zero trips confirmed zero trips persons who made no trips

 on their assigned travel day.

Proxy from memory Proxy from diary More trips reported. More

accurate reporting of trip

characteristics.

Trip definition Clearer trip Easier for respondent to

definition report trips. Interviewers

more attuned to pick up

incidental trips.

On-line edits Additional on-line More coherent trip reporting.

 edits Improved data quality.

 Completed household At least one person At least 50% of the A more accurate

 definition completed the travel- adults completed the representation of travel by

day interview travel-day interview the household unit.


 	




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APPENDIX 2

ADJUSTMENT OF 1990 TRAVEL DATA

	


 


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APPENDIX 2

ADJUSTMENT OF 1990 TRAVEL DATA

The 1995 Nationwide Personal Transportation Survey (NPTS) was a significant improvement

over previous surveys in the NPTS series. Different methods were used to ensure that more complete

trip reporting was obtained. Specifically,

- a travel diary was used by respondents in the 1995 survey, in lieu of memory recalling;

and

- “household rostering” was used to capture some trips that may otherwise have been

overlooked.

Although these improvements enhance the completeness and accuracy of trip reporting, they

prevent any direct comparisons between the 1990 and 1995 travel data. Any travel changes observed

between the 1990 and 1995 surveys now reflect not only actual changes in travel during the period but

also artifacts of differences in survey methodology. That is, any changes observed between the 1990

and 1995 travel data are presumably attributable to: (1) actual changes in travel behavior, (2) use of

travel diaries, (3) use of household rostering, and (4) other improvements in the 1995 survey method

such as a better coding scheme to decipher trip purposes. The latter is expected to have a smaller effect

than the first three factors. Since no data are available to quantify the impact of these “other”

improvements, their impacts are not evaluated in this exercise.

However, the improved coding scheme in 1995 had an effect on trip recording. In 1990,

1.9 billion trips were coded as “other” trip purpose. In 1995, this number was 700 million, a decline

of 64 percent. These “other” trips are those that can not be classified into any of the existing trip purpose

categories. Two reasons contribute to this substantial decrease in “other” trips. First, the information

was collected in the 1995 survey on “from” where the trip was originated and “to” where the trip was

	


 


destined. This type of “to” and “from” information enabled the trip purposes to be determined more

accurately. As a result, the number of trips with unspecified trip purposes decreased. Second, better

schemes to code trip purposes were used both during and after the data collection phase, significantly

reducing the ambiguity in trip purposes.

The reduction in trips with unspecified trip purposes presumably increases the number of trips

categorized into the proper trip purpose categories. Ideally, one should remove all artifacts that result

from an improved method. However, data to address the effects of each of the individual improvements

are extremely limited. Our approach was developed to remove as many artifacts that the data allow.

Specifically, our approach quantified and removed the effect of the travel diary and household trip

rostering on the amount and type of trips in the 1995 NPTS.

Adjustment Approach

To more accurately reflect travel trends, the 1990 travel data were adjusted to account for two

major changes in survey methodology: (1) travel diary, and (2) household rostering. In essence, the

1990 travel data were adjusted in such a way as if a travel diary and household rostering were used in

the 1990 survey. The theory is that more trips would have been recorded in the 1990 survey if travel

diaries were used. This theory is supported by data collected in the 1995 NPTS pre-test. Data from

the 1995 NPTS pre-test showed that travel diaries led to more complete reporting, particularly for

incidental trips, such as stopping at a convenience store, which are often forgotten and, therefore,

difficult to capture in a household travel survey. Household rostering is also expected to capture more

complete trip reporting by helping remind respondents of forgotten trips. Since data from the 1995

NPTS pre-test suggest that the impact of travel diary varies for different trip purposes, separate

adjustment factors were developed for different purposes.

Although more detailed trip purpose information was collected in the 1995 survey, for this

analysis trip purposes were grouped into four broad categories: (1) work and school, (2) shopping, (3)

family and personal business other than shopping, and (4) social and recreational. Separating shopping

 	





trips from trips taken for other family and personal businesses is based on the belief that travel diaries

and household rostering influence reporting on these trips differently. This appendix describes the

approach used to quantify impacts of travel diary and household rostering on the number of person trips

recorded by these purposes.

Rather than adjust travel data in all previous surveys (e.g., 1969, 1983 NPTS), only 1990 travel

data were adjusted. Both original and adjusted 1990 statistics are presented in this report. The user is

warned not to compare 1995 results to those from previous NPTS. For trend analysis, the 1995 results

should only be compared to the adjusted 1990 statistics.

Impact of Travel Diary on Trip Reporting

A methodological experiment was designed as part of the 1995 NPTS pre-test to test three

different survey methods: memory recall (n=875), memory jogger (n=729), and travel diary (n=708).

Although the pre-test sample sizes are not particularly large, these pretest data provide the only platform

to quantify the impact of travel diaries on trip reporting. On an individual basis, using a travel diary

indeed captures more trips than recalling the day’s trips from the memory (Table A2.1). It was found

that the diary method averaged 0.5 trips more per person per day than the recall, or retrospective method

[1]. In addition, travel diary use has greater impact on reporting non-work or non-school related trips

than on work or school trips. Its impact is the greatest for non-shopping types of family and personal

travel, such as visiting a doctor’s office, dropping off or picking up someone: 37 percent more such trips

were reported by using travel diaries than by recalling from memory.

The ratio of travel rates between those collected by travel diaries and those by recall

approximates the additional trips that would have been reported if travel diaries were used in the 1990

survey. Contrary to our assumption that travel diaries will not increase the number of work and school

trips reported, there were fewer work and school trips reported in the 1995 NPTS pre-test when travel

diaries were used rather than recall. For trip purposes other than work and school, travel diaries capture

	


 
	

more trips than recall (Table A2.1). Since travel diaries are not believed to improve the reporting of

non-incidental trips such as commute or school trips and since there is no other evidence supporting

a decrease in commute or school trips from 1990 to 1995, the impact of travel diaries on reporting these

trips is considered null, and no adjustment was made to the 1990 data.

Table A2.1 Annual Person Trips per Person by Survey Methods

Based on 1995 NPTS Pre-test Data

Travel Diary Recall % Different = [(1)-(2)]/(2)

(1) (2)

Work and school 312.50 341.64 -8.5%

Shopping 273.09 226.20 20.7%

Other family and personal 317.47 231.36 37.2%

Social and recreational 293.82 244.39 20.2%

Other 8.29 7.58 9.4%

ALL 1,205.17 1,051.17 14.7%

Impact of Household Rostering on Trip Reports

In “household rostering,” the interviewer has the benefit of trip data from all household

members who had already been interviewed. For example, suppose person #1 took a trip and reported

that persons #2 and #3 were on the trip with him. When persons #2 and #3 were interviewed, they were

asked to confirm that they were on the trip with person #1. If they were, the trip characteristics were

“copied” from person #1’s record to those of person #2 and person #3. If person #2 or person #3

indicated that they were not on the trip with person #1, this response was accepted. One benefit of

household rostering is that it aids the memory of the respondent and improves trip reporting.

 	






If household rostering had been used in the 1990 NPTS, how many more trips would have been

reported? Unfortunately, this question can not be answered directly due to the lack of data. Instead,

an indirect approach was developed. The basic idea behind this approach is simple: It is assumed that

household rostering does not increase trip reporting from 1990 to 1995 for trips where only one

household member is on the trip. Therefore, the travel trends observed between 1990 and 1995 in the

“non-accompany” trips are basically due to (1) changes in travel behavior, (2) use of travel diaries, and

(3) other improvements in the 1995 survey method (these effects being relatively inconsequential). It

should be emphasized that the “non-accompany” trips are not necessarily all single-occupant trips.

Rather, they are trips where only one household member is on the trip, with or without being

accompanied by non-household members. These trips are referred hereafter as “non-accompany

trips.”

After adjusting these “non-accompany” trips in 1990 for the impact of travel diaries, the

remaining difference between the 1990 and 1995 “non-accompany” trip rates is presumably

attributable to the change in travel during the period. Now, adjusting all of the 1990 trips to reflect the

impact of trip diary and the change in travel during the five year period, the remaining difference

between the 1995 survey data and the adjusted 1990 data presumably reflects the impact of household

rostering.

Table A2.2 illustrates the steps taken to estimate the real changes in trip rates observed in the

“non-accompany” trips from 1990 to 1995. The total numbers of “non-accompany” trips reported in

the 1990 NPTS are in Column 1. The impact of using travel diaries on reporting trips are listed in

Column 2. Adjusting 1990 data for diary impact, Column 3 reports the estimated number of trips by

purpose that would have been collected in 1990 had travel diaries been used. Comparing the adjusted

1990 figures (Column 3) to comparable 1995 data (Column 4), one can calculate the percentage change

in travel from 1990 to 1995 by trip purpose. The overall increase is nearly 30 percent, approximately

4.5 percent per year for the five year period.

	


 


Table A2.2 Estimated Travel Changes from 1990 to 1995

Based on trips without other household members “accompanied”

(1) (2) (3)=(1)x[(=1+(2)] (4) (5)=

[(4)-(3)]/(3)

 Purpose 1990 1-hhm1

 trips Diary 1990 1-hhm trips change

(000) Impact2 adjusted for 1995 1-hhm trips in travel

(%) diary impact (000) (%)

Work, School 62,973,929 0 62,973,929 84,974,961 34.9

Shopping 27,983,544 20.7 33,860,088 45,996,625 35.8

Other Fam/Per 33,237,593 37.2 45,535,502 58,602,172 28.7

Soc/Rec 33,166,604 20.2 39,799,925 46,509,286 16.9

Other 1,233,007 9.4 1,343,978 356,444 -73.5

TOTAL 158,594,677 182,383,879 236,439,488

1

 1-household-member (1-hhm) trips = Trips where no other household members “accompanied.”

2

 From Table 1.

This approach suggests that Americans as a whole took approximately 35 percent more

commute and school trips from 1990 to 1995. A number of factors could contribute to this increase

in the total number of work and school trips. For example, the number of workers increased by 11

percent during this period. Note that the number of “other” trips decreased by 74 percent due to a better

trip purpose coding scheme. The lack of appropriate and sufficient data prohibits an evaluation of the

impact of this improved coding scheme. Thus, no adjustments are made to 1990 trips categorized as

“other” trip purpose. These trips are a very small proportion of all trips.

With these calculations, the revised estimates of 1990 trips now reflect adjustments for (1) trip

diary and (2) change in travel. Presumably, the remaining difference between the 1995 survey data and

the adjusted 1990 data reflects the impact of household rostering. Table A2.3 demonstrates the steps

to estimate this effect. First, the number of trips collected in the 1990 survey was adjusted for the diary

impact (e.g., 21 percent for shopping trips) and for the change in travel between 1990 and 1995 (e.g.,

36 percent for shopping trips). It can be reasonably assumed that after this adjustment the 1990 data

 	





are almost comparable to the 1995 data except for the impact of household rostering. The percentage

difference between this adjusted 1990 data and the observed 1995 data is used to estimate the impact

of household rostering (Table A2.3). Based on this somewhat convoluted approach, we estimated that

approximately four percent more shopping trips would have been reported in the 1990 survey if

household rostering had been used. Again, the number of “other” trips decreased by 74 percent due

to a better trip purpose coding scheme. The lack of appropriate and sufficient data prohibits an

evaluation of the impact of this improved coding scheme. Thus, no adjustment is done to 1990 trips

categorized with the “other” trip purpose.

Table A2.3 Estimated Impacts of Household Rostering by Trip Purpose

(1) (2) (3) (4)= (5) (6)=

(1) x [(2)+(3)]/100 [(5)-(4)]/(4)

 1990 Diary change 1990 trips adjusted 1995 impact of

 Purpose Total Trips Impact in travel for diary impact Total Trips trip rostering

 (000) (%) (%) and % change in (000) (%)

travel

Work, School 82,240,011 0 34.9 110,941,885 110,115,282 -0.7

Shopping 47,056,740 20.7 35.8 73,643,798 76,688,225 4.1

Other Fam/Per 56,551,552 37.2 28.7 93,819,025 97,075,588 3.5

Soc/Rec 61,799,215 20.2 16.9 84,726,724 94,361,999 11.4

Other 1,914,779 9.4 -73.5 687,406 689,270 0.3

Adjustment Factors for 1990 Travel Data

By combining the impact of travel diary (Column 2 of Table A2.3) and the impact of household

rostering (Column 6 of Table A2.3), the factors used to adjust 1990 travel data range from no adjustment

for work and school trips to a 41 percent increase for trips taken for other family and personal business

(i.e., non-shopping trips) (Table A2.4). These adjustment factors suggest that between 1990 and 1995

the total number of person trips increased about 4.5 percent per year, compared to a rate of 2.6 percent

between 1969 and 1990. However, after taken into account the population increases over the years,

these adjustment factors suggest that a typical American increased his/her trips by 2.7 percent per year

	


 


(Table A2.5). This rate is comparable to the 2 percent increase observed between the 1969 and 1990

surveys.

Table A2.4 1990 Travel Data Adjustment

(Person trips in thousands)

 Purpose 1990 Trips Adjustment Adjusted 1995 Trips Average

(1) Factor 1990 Trips Annual %

(2) (1) × (2) Change

 Work, School 82,240,011 1.00 82,240,011 110,115,282 6.01

 Shopping 47,056,740 1.25 58,820,925 76,688,225 5.45

 Other Fam/Per Bus 56,551,552 1.41 79,737,688 97,075,588 4.01

 Social/Recreational 61,799,215 1.32 81,574,964 94,361,999 2.96

 Other 1,914,779 1.00 1,914,779 689,270 -

 TOTAL 249,562,297 304,288,367 378,930,363 4.49

Table A2.5 Daily Person Trips per Person

Adjusted 1990 and 1995 NPTS

 Purpose 1990 Trip Adjustment Factor Adjusted 1995 Trip Average Annual

Rate Diary+Rostering 1990 Rate Change Rate

Trip Rate (%)

 Work, School 1.015 1.00 1.015 1.248 4.22

 Shopping 0.580 1.25 0.725 0.869 3.70

 Other Fam/Per Bus 0.698 1.41 0.984 1.100 2.26

 Social/Recreational 0.762 1.32 1.006 1.070 1.24

 Other 0.024 1.00 0.024 0.008 --

 TOTAL 3.079 - 3.754 4.296 2.73

The fundamental assumption in this approach is that the changes observed in the “nonaccompany” trips reflect the changes observed in all trips. The validity of this assumption is checked

by first examining how representative the “non-accompany” trips are in both 1990 and 1995. “Nonaccompany” trips in both 1990 and 1995 account for no less than 50 percent of the total person trips

(Table A2.6), suggesting that using “non-accompany” trips to estimate the magnitude of travel changes

 	





in all trips appears to be reasonable. The validity of this assumption is further verified by checking

whether the “non-accompany” rate has changed from 1990 to 1995. More than three quarters of work

trips and school trips are not accompanied by other household members. This percentage remains

relatively stable from 1990 to 1995 (Table A2.6). Note that dropping off and picking up children from

schools are not considered “school trips” they are categorized under “Other family and personal

business.” Almost all trips remain somewhat stable for the non-accompany rate between 1990 and

1995 except social and recreational trips. There is a smaller percentage of social and recreational trips

in 1995 that went “unaccompanied by other households” than in 1990: 49 percent vs. 54 percent. That

data seem to support the idea that using only “non-accompany” trips to estimate travel changes between

1990 and 1995 is reasonable.

Table A2.6 One-Household-Member Person Trips, Total Person Trips,

and Non-Accompany Rate by Trip Purpose

1990 and 1995 NPTS

(Person Trips in thousands)

1990 NPTS 1995 NPTS

HH Non- Total Person Non- HH Non- Total Person Non-

 Purpose Accompany Trips Accompany Accompany Trips Accompany

Person Trips Rate Person Trips Rate

 Work, School 62,973,929 82,240,011 76.57% 84,974,961 110,115,282 77.17%

 Shopping 27,983,544 47,056,740 59.47% 45,996,625 76,688,225 59.98%

 Other Fam/Per Bus 33,237,593 56,551,552 58.77% 58,602,172 97,075,588 60.37%

 Social/Recreational 33,166,604 61,799,215 53.67% 46,509,286 94,361,999 49.29%

 Other 1,233,007 1,914,779 64.39% 356,444 689,270 51.71%

 TOTAL 158,594,677 249,562,297 63.55% 236,439,488 378,930,363 62.40%

This analysis was conducted using simple methods with the data available. These calculations

might raise as many questions as they have answered. Notwithstanding, this is the first attempt to

	


 


 	




explain the differences on travel that can be attributed to the improvements in the survey methods.

Hopefully more research on the effects of different survey methods will follow.


APPENDIX 3

DIFFERENCES IN WORKERS AND COMMUTE TRIPS

BETWEEN 1990 AND 1995 NPTS

	


 


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APPENDIX 3

DIFFERENCES IN WORKERS AND COMMUTE TRIPS

BETWEEN 1990 AND 1995 NPTS

Data from the NPTS indicate that overall personal travel increased at a surprising rate of 52

percent from 1990 to 1995. This rate implies an average annual increase of 8.7 percent—which is

unprecedented when compared to an average annual rate of 1.5 percent between 1983 and 1990 and

0.8 percent between 1977 and 1983. This unprecedented increase is attributable to two factors: the real

increase in travel, and “statistical artifacts” stemming from the different survey methods and definitions

used in 1990 and 1995. Appendix 2 details these two factors and describes how the 1990 survey data

are adjusted to ensure valid comparisons between the 1990 and 1995 survey data. However, this

adjustment was not made to commute and school trips because improved survey methods (use of travel

diaries and households rostering) are not believed to improve the reporting of non-incidental trips such

as commute or school trips.

This unprecedented increase is also observed in work trips, which include both journeys to

work and work-related trips. While the number of workers increased by an average of 2.2 percent each

year between 1990 and 1995, travel related to earning a living increased at an annual rate of 5.6 percent

for the total number of journey-to-work (JTW) vehicle trips, or 7.2 percent for the total JTW VMT

(Table A3.1). The changes in work-related trips are significantly more pronounced than those in JTW

(Table A3.1). This appendix identifies two sources potentially contributing to these increases in

commutes and work-related travel.

The first potential source is the recording of commercial driving. In 1990, commercial drivers

were instructed not to report trips as part of work. However, in 1995, trips as part of work (i.e.,

commercial driving) were recorded in the Travel Day file as long as the number of such trips taken is

10 or fewer. This difference between the two surveys in reporting commercial driving largely explains

	


 


 	




the annual increase of 60 percent in work-related trips among commercial drivers from 1990 to 1995

(Table A3.2).

Table A3.1 Statistics on Commutes and Work-Related Trips

1983, 1990, and 1995 NPTS

1983 1990 1995 Compounded Annual Change

83-90 90-95

 Workers (103

) 103,244 118,343 131,697 2.0% 2.2%

 Journey-to-work Trips

 Person Trips (106

) 46,493 50,314 66,901 1.1% 5.9%

 Vehicle Trips (106) 35,271 41,792 54,737 2.5% 5.6%

 VMT (106

) 301,644 453,042 642,610 6.0% 7.2%

 Work-related Trips

 Person Trips (106

) 5,283 3,529 9,860 -5.6% 22.8%

 Vehicle Trips (106

) 3,679 2,845 7,921 -3.6% 22.7%

 VMT (106) 42,090 42,336 137,867 0.01% 26.6%

Table A3.2. Annual Person Trips per Person

1990 and 1995 NPTS

 Trip Purpose Commercial Drivers Non-Commercial Drivers

1990 1995 Annual % 1990 1995 Annual %

 NPTS NPTS Difference NPTS NPTS Difference

 To/From

 Work 399.58 840.12 16.02% 431.51 468.16 1.64%

 Work-

 Related 32.23 343.19 60.49% 29.22 42.81 7.94%

Note: The number of commercial drivers and non-commercial drivers include only those workers age 16 or older.


However, some of these “work-related” trips were mis-coded as “to or from work,” or commute

trips. Two examples of such mis-coding are listed in Table A3.3. It is obvious from these examples

that all of the trips coded as “to and from work,” except the trips that were either to, or from, home,

should in fact have been coded as “work-related.” To gauge the magnitude of this mis-coding among

all commercial drivers would involve manually checking individual trips, which can be very tedious.

Thus, the exact impact of this mis-coding on the increase in commutes between 1990 and 1995 is

unknown at this time. However, a preliminary analysis was conducted on workers who took unusually

large numbers of commute trips in a day. Specifically, the analysis focused on the workers who took

four or more commute trips in a day (3.5 percent of all workers). Rather than assuming that anyone

who reported more than four commute trips had their 5th and 6th commutes mis-coded, a set of additional

ad-hoc criteria were used. A commute trip was considered mis-coded if it was the 5th or greater

commute trip taken in a day (e.g., the 6th or the 7th, etc.), and it used an unusual mode such as school

bus, airplane, and a truck other than a pickup truck, and the mode used was different from the one used

in the previous commute trip. By limiting the trips to those that meet the above criteria, we believe that

between 70 percent and 80 percent of those trips are mis-coded. However, since only less than one

percent of all trips meet the above criteria, the impact of potentially mis-coding is inconsequential. If

the number of daily commute trips per person is limited to four, then commute trips are estimated to

increase between 1990 and 1995 at an average annual rate of 5.8 percent, rather than the 5.9 percent

as reported in Table A3.1.

In addition to this difference in data recording, two definitional differences potentially bias any

comparisons between 1990 and 1995 on workers and commutes. They are: the definition of workers,

and the definition of commute trips. Unfortunately, lack of benchmark data prohibits any adjustments

to the 1990 data to account for the definitional differences.

	


 
	

Table A3.3. Example of Two Persons Taking Trips That Were Classified as Commute Trips

1995 NPTS

HOUSE ID PERSON ID 95 Trip WHY TO WHY FROM Mode of Start Time

Purpose Transportation of Trip

 1059377 1 To work To work Home Pickup 6:15

1059377 1 To work To work To work School Bus 6:40

 1059377 1 To work To work To work School Bus 7:20

 1059377 1 To work To work To work School Bus 7:55

 1059377 1 To work To work To work School Bus 8:20

 1059377 1 To work To work To work School Bus 9:00

 1059377 1 Home Home To work Pickup 9:15

 1059377 1 To work To work Home Auto 13:45

 1059377 1 To work To work To work School Bus 14:20

 1059377 1 To work To work To work School Bus 15:05

 1059377 1 To work To work To work School Bus 15:30

 1059377 1 To work To work To work School Bus 15:50

 1059377 1 Home Home To work Auto 16:45

	







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HOUSE ID PERSON ID 95 Trip WHY TO WHY FROM Mode of Start Time

Purpose Transportation of Trip

 1142363 1 To work To work Home Pickup 8:00

1142363 1 To work To work To work Other trk 9:15

 1142363 1 To work To work To work Other trk 10:05

 1142363 1 To work To work To work Other trk 10:50

 1142363 1 To work To work To work Other trk 11:30

 1142363 1 To work To work To work Other trk 12:15

 1142363 1 To work To work To work Other trk 13:00

 1142363 1 To work To work To work Other trk 13:40

 1142363 1 To work To work To work Other trk 14:00

 1142363 1 To work To work To work Other trk 14:15

 1142363 1 To work To work To work Other trk 15:00

 1142363 1 To work To work To work Other trk 15:15

 1142363 1 To work To work To work Other trk 15:35

 1142363 1 Home Home To work Pickup 16:30

+

 




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	&0(1

	


 


Definition of Workers

In the 1990 NPTS, a respondent was defined as a worker if:

• the respondent was working most of the previous week (a one-week period prior to the

interview),

• the respondent was with a job but not at work most of the previous week, or

• the respondent was doing something else most of the previous week (e.g. looking for

work, keeping house, going to school, etc.), but responded “Yes” to:

(a) “Did you do any work last week, not counting work around the house?”, or

(b) “Did you have a job or business from which you were temporarily absent last

week?”

In the 1995 survey, a worker was defined based on the response to a single question, “Do you

have a full or part-time job working for pay or profit?” Because of the difference in the definition of

a worker between the two surveys, any comparisons of the difference in the number of workers

between the 1990 and 1995 NPTS should be made with caution. Different estimates of the number

of workers are presented in Table A3.4. Apparently, the more stringent criteria used in 1990 yield an

estimate of the total number of workers that is considerably closer to that estimated by the Bureau of

Labor Statistics.

 	





	


 

Table A3.4 Number of Workers (in ‘000)

1983, 1990, and 1995 NPTS and BLS Data

NPTS BLS1

 Data % Different

1983 103,244 100,834 2.4%

1990 118,343 118,793 -0.4%

1995 131,697 124,900 5.4%

1 U.S. Bureau of Labor Statistics, Bulletin 2306; and

Employment and Earnings, monthly, January issues. BLS

data beginning 1994, not directly comparable with earlier

years. See text, section 13, and February 1994 issue of

Employment and Earnings.

Definition of Commute Trips

Commute trips include trips from home to work and trips from work to home. In the 1990

NPTS, trip purposes were “activity-based” and were determined using a round-trip scheme. Using this

scheme, trips to and from work were both coded as “to and from work” and a commute trip was defined

as a trip taken with a purpose categorized as “to or from work.” This was mainly done to assign both

parts of the round-trip to the reason the travel was made, thus avoiding the use of “return home” or

“return to work.” By 1995, the basis for determining trip purpose was significantly different from that

used in the 1990 NPTS. The 1995 NPTS was “destination-based” and defined trip purposes as to why

the one-way trip was made. Therefore, each trip purpose was defined based on the destination of that

one-way trip. The reasons for this coding scheme are: (1) to obtain better data on trip chaining, (2) to

have a coding scheme that was more direct and precise, and (3) to have a coding scheme that was easier

for the interviewer to apply.

To apply the 1990 trip-purpose coding scheme to the 1995 NPTS data, a considerable number

of intermediate steps are required. For example, in the 1990 trip-purpose coding scheme, if there was


more than one trip before the return-home trip, then the destination where the longest time was spent

was the “purpose” of that trip. Thus, the steps in the recoding process are to: (1) first create trip chains,

(2) measure time spent at each destination, and, finally, (3) determine the main purpose of the trip. These

steps can be illustrated by an example (Figure A3.1). In this example, the traveler stops on the way to

work to drop off a child at school; continues on to work; runs some errands during lunch by shopping

at a store and banking at a bank. On her way home, she stops at the grocery store to shop, then to school

to pick up her child, and finally returns home. All her trips during this day are enumerated in a tabular

format, under both the 1990 and 1995 definitions. Under the 1990 trip-purpose coding scheme, Trip

No. 5 will be for “shopping” if more time is spent at the store than at the bank. However, if more time

is spent at the bank than at the store, then the trip purpose for Trip No. 5 will be “other family and

personal business” according to the 1990 trip-purpose definition. The same logic applies to Trip No.

8. Because it is most common to spend the longest time at work, rather than at the store (Trip No. 6)

or at school (Trip No. 7), the purpose for Trip No. 8 is “to or from work.” Appendix M of the 1995

NPTS User’s Guide provides more detailed information on the coding of the 1995 and 1990 trip

purposes.

Although significantly improving the way trips are characterized with respect to why travel

takes place, this re-coding scheme introduces discrepancies between the two surveys. Re-coding the

1995 trip purposes is a complicated process. Table A3.5 illustrates an example of how 1995 data could

be coded incorrectly. Incidentally, all trips in Table A3.5 qualify as commute trips because their

purposes, based on the 1990 definition, are “to and from work.” To investigate the likelihood of miscoding trip purposes, information on the “to” and “from” purposes is used. In 1995, additional

information was collected on individual trips with respect to the destination “to” which travel takes

place and the destination “from” which travel returns. All of these commute person trips (with a 1990

trip purpose of “to and from work”) have the “to” part of the trip as “return to work” (Column 2). The

primary purpose for the trip can then be ascertained by the information on the “from” portion of the

trip. For example, there are 102 trips that were “return to work” “from work”—which is highly

illogical. One reasonable interpretation of these 102 trips would be “return to work” from “work-

 	





Figure A3.1 An Example to Illustrate Trip-Purpose Coding Schemes

 Trip Trip Purpose

 Number Description 1990 Definition 1995 Definition

1. from home to child’s school Other family/personal Take someone

business somwhere

2. from child’s school to work To or from work To work

 3. from work to store Shopping Shopping

4. from store to bank Other family/personal Other family/personal

business business

5. from bank back to work Shopping* Return to work

6. from work to store Shopping Shopping

7. from store to child’s school Other family/personal Pick up someone

business

8. from child’s school to home To or from work Home

* If more time is spent at the store than at the bank.

	


 


Table A3.5 Example of Presumably Incorrectly-Coded 1995 Commute Trips

(With the 1990 trip purpose of “To and From Work”)

 1995 Trip-Purpose Definition 1990 Trip-Purpose Definition

“to” part of the trip Currently coded Presumably correct

“from” part of the trip = “return to work” trip purpose 1990 trip purpose

To work 102 To and from work Work-related business

Work related business 1,490 „ Work-related business

Return to work 35 „ Work-related business

Shopping 58 „ Shopping

School 3 „ School

Religious activity 2 „ Religious activity

Medical or dental 6 „ Medical or dental

Other family/personal 64 „ Other family/per bus

business

Take someone 20 „ Other family/per bus

somewhere

Pick up someone 0 „ Other family/per bus

Vacation 0 „ Vacation

Visit friends or 13 „ Visit friends or relatives

relatives

Went out to eat 24 „ Other soc/rec

Other 12 „ Other soc/rec

social/recreational

Home 1,091 „ Other family/per bus

Not ascertained 19 „ Not ascertained

ALL 2,938 „ ALL

 	





related business.” If these trips’ purposes are coded correctly, then they would not count as commute

trips. Another example are the 58 trips which “return to work” from “shopping.” If these trips are

correctly coded, then they should be “shopping” trips rather than “to and from work” trips which qualify

them as commute trips. The third column of Table A3.5 gives the trip purposes that are probable

correct. Should all the trips reported in Table A3.5 be coded correctly, they would be disqualified as

commute trips, partially explaining the unprecedented increase in commutes from 1990 to 1995.

Unfortunately, the magnitude of the mis-coding of 1995 trips can not be readily quantified.

Another possible explanation of the apparently great increase in work trips is the large

percentage of non-workers who reportedly commuted to work on their designated travel day. This

percentage is almost always higher in 1995 than in 1990 for every age group (Table A3.6).

However, the difference between 1990 and 1995 increases substantially for age categories older than

55 years. The reasons for these differences are unclear. One plausible explanation is that more people

55 years old and over volunteered for work without pay in 1995 than in 1990. Persons who perform

unpaid volunteer work might not consider themselves a “worker” but consider daily travel to their

unpaid volunteer work as “going to work.” Unfortunately, this possible explanation can not be

substantiated. Although three surveys on voluntarism have been conducted through the Current

Population Survey in 1965, 1974 and 1989, each of these surveys differs in terms of questions, concepts

and coverage. Consequently, their usefulness for identifying changes in volunteer behavior over time

is very limited.

In summary, any comparisons on statistics related to workers and commutes between 1990 and

1995 should include a caveat indicating that part of the differences between the two surveys are due

to (1) different definitions of workers and trip purposes in the two surveys, and (2) the way commercial

driving was recorded, and not due to actual changes in travel or in social economy.

	


 


 	




Table A3.6 Percent of Non-Workers Commute to Work

1990 and 1995 NPTS

Age of Worker 1990 NPTS 1995 NPTS

16 to 19 4.78% 4.74%

20 to 24 1.51% 2.71%

25 to 29 0.93% 0.94%

30 to 34 0.87% 1.12%

35 to 39 0.91% 1.12%

40 to 44 1.02% 0.83%

45 to 49 0.70% 1.03%

50 to 54 1.39% 1.51%

55 to 59 1.41% 4.05%

60 to 64 2.62% 6.64%

65 to 69 7.24% 15.12%

70 to 74 6.56% 27.23%

75 to 79 15.23% 33.66%

80 to 84 24.39% 58.95%

85+ 53.99% 64.02%


APPENDIX 4

DIFFERENCES IN METROPOLITAN AREA DEFINITIONS

BETWEEN 1983 AND 1990 NPTS

	


 


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APPENDIX 4

DIFFERENCES IN METROPOLITAN AREA DEFINITIONS

BETWEEN 1983 AND 1990 NPTS

Between 1983 and 1990, the United States Office of Management and Budget changed the

definition of a Metropolitan Statistical Area (MSA). This change complicates any comparisons of

metropolitan area data from the 1983 and 1990 NPTS. In 1983 all areas were divided into combinations

of counties called Standard Metropolitan Statistical Areas (SMSAs), with the exception that SMSAs

in New England consisted of cities and towns. Typically, metropolitan areas are redefined following

each census, resulting in additions or subtractions of counties, New England towns, and central cities.

Substantial changes were made following the 1980 Census because of considerable revisions in the

standards used by the Office of Management and Budget to define the areas.

By 1990 the term “metropolitan statistical area” (MSA) replaced “standard metropolitan

statistical area” (SMSA). An optional two-tiered metropolitan structure was introduced for MSAs of

a million people or more. These MSAs could be subdivided into primary MSAs (PMSAs) if certain

decentralization conditions were met and if the locality desired such subdivisions. If PMSA’s were

defined within an MSA, then the MSA became a consolidated MSA (CMSA).

Of the 318 preexisting SMSAs, 53 became PMSAs within 15 CMSAs, and 8 new PMSAs

were established within these CMSAs. In addition, five preexisting SMSAs became CMSAs which

were further subdivided into ten PMSAs. As the result of these redefinitions, there were 20 CMSAs

with 71 component PMSAs when the 1990 NPTS was conducted. Among these 20 CMSAs, there

were ten with a population of more than three million. These ten CMSAs were made up of 48 PMSAs,

most of which did not by themselves have a population more than three million. Moreover, there was

one MSA in 1990 with a population of more than three million.

	


 


 	




In the 1990 and 1995 NPTS, the variable MSASIZE was given a population size value based

on its MSA or CMSA size. Therefore, if a household was located in an area within a PMSA of less

than three million, but its CMSA had a population of more than three million, then the household was

categorized as being located in an MSA of three+ million. In 1983 and all previous NPTS surveys,

however, only the SMSAs which by themselves had a population of more than three million were

categorized as being “3+ million.” The implication of this definitional change on the NPTS data is that

many more households were estimated by the 1990 and 1995 data as being located within metropolitan

areas with a population of more than three million than that estimated by the previous NPTS surveys.


APPENDIX 5

STANDARD ERROR TABLES

	


 


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APPENDIX 5

STANDARD ERROR TABLES

The final adjusted weights are used in calculating parameter estimates and their sample

variance. The standard error estimates shown in the following tables were obtained using the ultimate

cluster variance formula. Further information on calculating standard errors using this method can be

found in Appendix F and Appendix G of the CENVAR, Variance Calculation System User’s Guide

(U.S. Department of Commerce, Bureau of the Census, International Systems Team, Washington, DC,

January, 1995.)

The standard errors that are shown in the following tables reflect the sampling error and also

the variation in estimates due to some nonsampling errors. Sampling error is due to variability between

estimates from all other possible samples of the same size that could have been selected using the same

sample design (e.g. variation that occurred by chance because a sample was surveyed rather than the

entire household population). Estimates that were derived from any of these different samples would

differ from one another. This variability, along with some nonsampling error, are measured by the

standard error. Nonsampling error can be attributed to several sources including the following:

• The inability to obtain information about all cases in the sample unit and item (nonresponse)

• The inability to obtain correct information from respondents

• Errors made in data collection such as recording and coding errors

• Errors made in data processing

• Failure to represent all units with the sample (noncoverage)

Sampling errors shown in this report are primarily measures of sampling variability although

they may include some nonsampling error. Thus, the accuracy of the estimates given is dependent on

	


 


the sampling error and nonsampling errors which are measured by the standard error, and also on the

biases and nonsampling errors which are not measured by the standard error.

The standard error of these estimates can be used to construct an interval around specific

estimates. This interval will include, with a given amount of confidence, the true population value.

About 68 percent of the intervals, created by subtracting one standard error and adding one standard

error, will include the true population value. About 95 percent of the intervals, created by subtracting

two standard errors and adding two standard errors, will include the true population value, and about

99.75 percent of the intervals, created by subtracting and adding three standard errors, will include the

true population value. Thus, one can state, with a given percent of confidence (as stated above) that the

computed interval will contain the true population value.

An example of how these standard errors could be used is as follows. One may want to know

the annual person miles traveled per household for social and recreational purposes. The estimate of

the total number of annual person miles of travel per household for social and recreational purposes in

1995 is 10,571. The standard error for this estimate, as found in Standard Errors for Table 5, is 283.76.

To construct an interval that would include the true population value about 68 percent of the time, one

would calculate: 10,571 ± (1)283.76. Therefore, a 68 percent confidence interval for the true person

miles traveled per household, as shown by this data, would be included in the interval 10,287 to 10,855

person miles of travel per person. An interval that would include the true person miles per household

about 95 percent of the time would be constructed by solving: 10,571 ± (2)283.76. Hence, a 95 percent

confidence interval for the true number of person miles of travel per household for social and

recreational purposes is in the interval from 10,003 to 11,139 person miles per household.

 	





	


 

Standard Errors for Table 1

Summary Statistics on Demographic Characteristics and Total Travel,

1995 NPTS

Standard Errors for:

HOUSEHOLDS (000)

All 330

1 person 386

2 persons 330

3 persons 280

4+ persons 341

 PERSONS (000)

All Persons 5 or older 1,281

Under 16 675

16-19 330

20-34 738

35-64 693

65+ 460

All Males 5 or older 808

All Females 5 or older 778

LICENSED DRIVERS (000)

All 846

Men 596

Women 525

WORKERS (000)

All 864

Men 589

Women 524

HOUSEHOLD VEHICLES (000)

880

HOUSEHOLD VEHICLE TRIPS (000,000)

1,600

HOUSEHOLD VMT (000,000)

23,782

PERSON TRIPS (000,000)

2,645

PERSON MILES OF TRAVEL (000,000)

49,131
	

 	




Standard Errors for Table 4

Average Annual PMT, Person Trips and Trip Length by Trip Purpose

1995 NPTS

 Stderr for Avg Annual PMT per HH

All Purposes 496.32

To/From Work 122.92

Work Related Business 113.88

Shopping 126.00

All Other Fam/Per Business 272.25

School/Church 69.83

Social and Recreational 283.76

Other 49.89

 Stderr for Avg Annual Person Trips per HH

All Purposes 26.72

To/From Work 6.53

Work Related Business 2.86

Shopping 8.50

All Other Fam/Per Business 10.10

School/Church 5.81

Social and Recreational 10.83

Other 0.57

 Stderr for Avg Person Trip Length

All Purposes 0.12

To/From Work 0.15

Work Related Business 1.08

Shopping 0.15

All Other Fam/Per Business 0.27

School/Church 0.18

Social and Recreational 0.28

Other 8.32



	


 

Standard Errors for Table 5

Average Annual VMT, Vehicle Trips, and Trip Length

by Selected Trip Purposes

1995 NPTS

 Stderr for Avg Annual VMT per HH

All Purposes 240.25

To or From Work 106.32

Shopping 61.52

Other Fam & Personal Business 95.27

Social and Recreational 114.44

Stderr for Avg Annual Vehicle Trips per HH

All Purposes 16.17

To or From Work 5.71

Shopping 5.49

Other Fam. & Personal Business 7.01

Social and Recreational 4.97

 Stderr for Avg Vehicle Trip Length

All Purposes 0.09

To or From Work 0.16

Shopping 0.11

Other Fam. & Personal Business 0.14

Social and Recreational 0.25


 	




Standard Errors for Table 8

Total Person Trips by Mode of Transportation and Trip Purpose

1995 NPTS

(millions)

Standard Errors

Private Public Transit Other Total

Total

2,390 223 633 2,645

To or From Work

611 101 124 647

Work Related

Business 267 27 67 283

Family and

Personal Business 1,509 106 285 1,594

School/Church 467 62 271 576

Social and 1,007 93 336 1,165

Recreational

Other 50 5 18 56


Standard Errors for Table 15

Average Vehicle Occupancy for Selected Trip Purposes

(person miles per vehicle mile)

Standard Errors

To or From Work 0.008

Shopping 0.028

Other Family or

Personal Business 0.030

Social and Recreational 0.032

All Purposes 0.013

	


 


 	




Standard Errors for Table 16

Households by Availability of Household Vehicle

1995 NPTS

(thousands)

Standard Errors for Households with -

No Vehicle 213

One Vehicle 400

Two Vehicles 370

Three or More Vehicles 286

ALL 330

Vehicles Per Household .0089


	


 

Standard Errors for Table 19

Number of Household Vehicles and Average Vehicle Age by Vehicle Type

1995 NPTS

Standard Errors for Vehicles (000)

Total 880

Auto 687

Van 273

Sport Utility 258

Pickup 407

Other Truck 75

RV/Motor Home 76

Motorcycle 112

Other 25

Standard Errors for Avg Vehicle Age

Total 0.042

Auto 0.048

Van 0.109

Sport Utility 0.122

Pickup 0.108

Other Truck 0.945

RV/Motor Home 0.553

Note:

• Standard errors are generated for number of household vehicles and average vehicle age, not on

percentage of household vehicles and vehicle age.


Standard Errors for Table 21

Average Annual Miles per Vehicle by Vehicle Age

(Vehicle Owner’s Estimate)

1995 NPTS

Standard Errors for Vehicles

 0 to 2 years 224.24

 3 to 5 years 153.95

 6 to 9 years 155.52

10 or more years 126.54

ALL 85.83

 	





	


 

Standard Errors for Table 22

Average Annual Miles per Licensed Driver by Driver Age and Gender

(Self Estimate)

1995 NPTS

Driver Age

Stderr for ALL

16 to 19 392

20 to 34 213

35 to 54 156

55 to 64 239

65+ 158

ALL 103

Stderr for Men

16 to 19 568

20 to 34 335

35 to 54 250

55 to 64 414

65+ 268

ALL 161

Stderr for Women

16 to 19 509

20 to 34 208

35 to 54 150

55 to 64 192

65+ 122

ALL 99


 	




Standard Errors for Table 24

Number of Workers by Usual Mode

1995 NPTS

(thousands)

Mode of Transportation Stderr

All Modes 864

Auto, Truck, Van, or Utility Vehicle 801

Public Transit 204

Other 171

Note:

• Standard errors are generated for number of workers by usual mode, not on percentage of workers by usual mode.


	


 

Standard Errors for Table 28

Daily Travel Statistics by Weekday vs Weekend

1995 NPTS

Standard Errors for Daily Travel Statistics Weekday Weekend

Vehicle Trips per Driver 0.023 0.031

Daily Work Trips 0.009 0.011

Daily Non-Work Trips 0.013 0.018

VMT per Driver 0.392 0.633

Average Vehicle Trip Length 0.101 0.207

Average Time Spent Driving (in minutes) 0.492 0.780

Person Trips per Person 0.035 0.056

PMT per Person 0.597 1.252

Average Person Trip Length 0.127 0.294
	

 	








APPENDIX 6

SEGMENTED TRIPS IN NPTS

	


 


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APPENDIX 6

SEGMENTED TRIPS IN NPTS

WHAT

In the 1990 and 1995 NPTS, certain trips were given “segmented” treatment, that is, they were

broken into component parts. A trip was given segmented treatment if both of the following conditions

occurred:

• there was a change of vehicle or a change of mode on the trip, AND

• one of the modes used was a public transportation mode (bus, subway, elevated rail,

commuter train, streetcar or trolley).

WHY

Transportation planners and researchers have a high degree of interest in multi-modal trips, and

the data from segmented trips can help in answering questions such as “What access modes are used

to get to the bus, subway and commuter train?” or “How does travel time of segmented trips compare

with non-segmented?” Certain trips were given segmented treatment in order to get more complete data

on multi-modal trips and on the use of public transportation. In earlier NPTS surveys, if more than one

mode was used on a trip, the entire trip was considered to be made on the mode that was used for the

longest distance. However, this procedure had the effect of undercounting the use of transit. For

example, if you walked to the bus stop, took the bus to a subway station, and took the subway to work,

the entire trip would have been considered a subway trip (assuming this was the longest segment) and

the walk and bus portions would have been ignored.

	


 


 	




HOW

If a trip met the two conditions above, it would be given segmented treatment. First,

characteristics of the trip as a whole would be collected, such as purpose, number of people on the trip,

starting time of the trip, whether it was a home-based trip, etc. Second, each time there was a change

of mode (e.g. auto to commuter train) or a change of vehicle (e.g. one bus to another), it would be

considered a segment.

Certain information was collected on each segment, namely, the mode used, the starting time

of the segment, the length of the segment in minutes and, if the segment was on transit, the waiting time

and whether the respondent sat or stood on the segment.


APPENDIX 7

REVISED AVERAGE ANNUAL MILES DRIVEN PER DRIVER

	


 


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APPENDIX 7

REVISED AVERAGE ANNUAL MILES DRIVEN PER DRIVER

Why the revision?

Numerous data users had questioned the earlier annual average miles driven because there were

per driver declines between 1990 and 1995 in virtually all age/gender categories other than men 65 or

older. This seemed incongruous, given the overall strong increase in travel during this time. Upon

checking the reasons for the declines in average annual miles per driver, it was discovered that in 1990

only two percent of the drivers reported driving no miles during the year, while this rose to nine percent

in 1995. Further, many of the nine percent of 1995 drivers indicated that they actually did drive, either

on their assigned Travel Day or as the primary driver of one of the household vehicles which reported

mileage. Those drivers that reported not driving but also showed up as having driven, were moved

from ‘no miles’ to ‘miles not reported.’ After this change was made, only about one and a half percent

of all drivers remained in the “no miles category”.

What the revised data means

The revised data show modest increases of generally less than ten percent for most age/gender

groups. The big exception is the 16-19 year-old group, where miles declined between 1990 and 1995.

This may be due to delayed licensing laws and/or higher auto insurance premiums. However, a number

of reviewers questioned this decline in teenage driving. The driving reported by this group on their

assigned travel day was reviewed and also showed a slight decline. But there was still concern that this

decline was a survey affect, not a real decline. A number of other survey attributes were analyzed,

including the degree of proxy reporting by teenagers in 1990 and 1995 and whether they were a

primary driver of a household vehicle. Nothing conclusive was found. Thus, use the data on 16-19

year-olds with caution.

	


 


 	




For men, the most dramatic increases in travel were for those 65 and older. Younger men,

namely those 20-54 may finally be reaching saturation in their travel. Women’s travel shows a very

different pattern, with declines in the youngest group (16-19), consistent increases of 7 to 8 percent for

those 20 through 64, and no change in average travel for those 65 and older. Given what we know

about older women, it is somewhat surprising that their average driving did not grow. However,

perhaps the fact of their increased health and financial status is offset by the more women in this group

staying alive longer, keeping their driver’s licenses, but not necessarily still driving.

Revised Annual Miles Driven per Driver

by Driver’s Age and Gender

Male Female

Age 1990 1995 %change 1990 1995 %change

16-19 9,543 8,206 -14.0% 7,387 6,873 -7.0%

20-34 18,310 17,976 -1.8% 11,174 12,004 +7.4%

35-54 18,871 18,858 0.0% 10,539 11,464 +8.8%

55-64 15,224 15,859 +4.2% 7,211 7,780 +7.9%

65+ 9,162 10,304 +12.5% 4,750 4,785 +0.8%

ALL 16,536 16,550 0.0% 9,528 10,142 +6.5%
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