Steven E. Polzin, PhD. Center for Urban Transportation Research University of South Florida April 2012

Fundamentals on Interpreting NHTS Data

“If you torture the data long enough, nature will confess.”

Ronald Coase – 1991 Noble Prize in Economics

“If you torture the data long enough you can make it confess to anything.”

Alan Pisarski – No Noble Prizes

Travel Trends

0

50

100

150

200

250

300

350

400

450

1977 1983 1990 1995 2001 2008

Ann

ual H

ours

per

Per

son

Travel Time per Capita

0

0

0

0

0

0

0

0

0

0

1969 1977 1983 1990 1995 2001 2008

Ann

ual V

MT

VMT per Person

-

500,000

1,000,000

1,500,000

2,000,000

2,500,000

1969 1977 1983 1990 1995 2001 2008

VMT in Millions

-

0.50

1.00

1.50

2.00

2.50

1969 1977 1983 1990 1995 2001 2008

PMT/VMT

PMT and VMT per Capita by Age

0

5000

10000

15000

20000

25000 2001 Per Capita VMT 2001 Per Capita PMT

2008 Per Capita VMT 2008 Per Capita PMT

The NHTS Transit Sample

Select Metro Areas Unweighted Transit Trips

Share of National Transit Sample

Weighted Share of National Transit Sample

Share of National

Population

UZA Share of NTD

National Trips

Boston--Worchester--Lawrence, MA--NH--ME--CT 60 0.7% 2.9% 2.0% 3.7%

Charlotte--Gastonia--Rock Hill, NC--SC 7 0.1% 0.1% 0.6% 0.2%

Houston--Galveston--Brazoria, TX 175 2.1% 1.0% 1.6% 0.8%

Louisville, KY--IN 0 0.0% 0.0% 0.3% 0.2%

Minneapolis--St. Paul, MN--WI 11 0.1% 0.4% 1.1% 0.9% New York--Northern New Jersey--Long Island, NY--NJ--CT--PA 2552 29.9% 33.1% 7.3% 40.5%

Phoenix--Mesa, AZ 237 2.8% 0.3% 1.4% 0.7%

Salt Lake City--Ogden, UT 20 0.2% 0.5% 0.6% 0.3%

Tampa--St. Petersburg--Clearwater, FL 59 0.7% 0.3% 0.9% 0.3%

Trip Rate and Length

1067

1054

1371

1568

1449

1385

9.47 8.68 9.29 9.00

10.78 9.52

0

5

10

15

20

0

200

400

600

800

1000

1200

1400

1600

1800

1977 1983 1990 Adj. 1995 2001 2008

Trip

Len

gth

Ann

ual T

rips

per

Per

son

5+

NPTS and NHTS Work Trip Walking Mode Shares

1969 5.00%

1977 4.60% 1983

4.10% 1990 3.70%

1995 2.60%

2001 2.81%

2008 2.82%

1983 4.50% 1990

4.00%

1995 2.30%

2001 2.92%

2008 3.03%

0%

1%

2%

3%

4%

5%

6%

1969

19

70

1971

19

72

1973

19

74

1975

19

76

1977

19

78

1979

19

80

1981

19

82

1983

19

84

1985

19

86

1987

19

88

1989

19

90

1991

19

92

1993

19

94

1995

19

96

1997

19

98

1999

20

00

2001

20

02

2003

20

04

2005

20

06

2007

20

08

2009

Perc

ent W

alki

ng to

Wor

k

Work Trip "Usual Mode"

Work Trip Actual Mode

Walk is 10.95% of all trips in 2008

8.90%

6.40%

5.30%

4.70% 4.99% 4.60%

3.56% 3.67%

3.68%

3.40%

2.70% 2.70% 2.20% 1.81% 1.56%

1.92%

1.76%

5.11% 5.05%

5.13%

0%

1%

2%

3%

4%

5%

6%

7%

8%

9%

10%

Perc

ent o

n Tr

ansi

t

Census/ACS Journey to Work, Usual Mode

NPTS/NHTS Work Trips, Survey Day

NPTS/NHTS All Trips

NHTS 2001 Adjusted

NHTS Work Trip, Work Trip Usual Mode

Transit Mode Share Trends

Vehicle Occupancies - NHTS

1.40 1.30 1.30

1.20 1.20 1.20 1.13

1.90 1.90

1.80 1.70

1.59 1.64

1.67

0.80

1.00

1.20

1.40

1.60

1.80

2.00

2.20

1969 1974 1979 1984 1989 1994 1999 2004 2009

Occ

upan

cy

Work Trip

All Trips

Carpooling Mode Share (ACS)

20.4% 19.7%

13.4% 12.2%

10.7%

0%

5%

10%

15%

20%

25%

1970 1980 1990 2000 2008

Perc

ent C

arpo

olin

g to

Wor

k

Vehicle Availability

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1969 1974 1979 1984 1989 1994 1999 2004 2009

Vehi

cles

per

Vehicles per worker

Vehicles per person 16 and older

Vehicles per person

Vehicles per driver

Declining Zero-Vehicle Households?

0%

5%

10%

15%

20%

25%

1960 1970 1980 1990 2000 2010

Per

cent

NPTS/NHTS Census ACS

Source: CUTR analysis of NHTS ,NPTS,U.S. Census Bureau and 2002-09 ACS

Household Vehicle Ownership Distribution Household Percents

National Household Vehicle Ownership Distribution, 2009

HH Vehicles Number of Adults in HH 1 2 3 4 5+ All

0 5.79% 2.28% 0.38% 0.19% 0.05% 8.69%

1 20.40% 10.18% 1.31% 0.33% 0.06% 32.28%

2 3.66% 29.04% 2.92% 0.62% 0.08% 36.32%

3 0.74% 9.06% 3.72% 0.78% 0.09% 14.39%

4 0.21% 2.58% 1.54% 0.82% 0.13% 5.30%

5+ 0.14% 1.40% 0.82% 0.49% 0.17% 3.02%

All 30.96% 54.54% 10.69% 3.23% 0.58% 100.00%

20.66% More cars than adults

54.16% Cars equals adults

16.50% Fewer cars than adults

8.69% Zero cars

Who is Using

Transit?

Transit Market Share by Car Availability

32.5%

15.6%

3.3% 13.7%

14.4%

7.2%

13.4%

2008

0 Cars, 1 or More

0 Cars, 0 Workers

2+ More Workers than Autos

1 More Worker than

Cars is Greater than Workers

Cars =

1 Car, 1

34.9%

9.7%

8.2% 15.4%

11.2%

9.4%

11.2%

2001

0 Cars, 1 or More

Workers

0 Cars, 0 Workers

2+ More Workers than

Autos 1 More Worker than

Cars is Greater than Workers

Cars = Workers

1 Car, 1 Worker

0 car household riders make up 44.6% of riders

0 car household

riders make up 48.1% of riders

0

5

10

15

20

25

30

0 Cars, 1 or More Workers

0 cars, 0 Workers

2+ More Workers than

Autos

1 More Worker than

Autos

Cars is Greater Than

Workers

Cars = Workers

1 Car, 1 Worker

Mod

e Sh

are

Perc

ent

2001

2008

Transit Mode Share by Vehicle Availability

Shortage of Vehicles

Transit Mode Share by Income

5.98

2.31

1.05

1.92

5.32

1.38

0.91

1.57

4.98

1.57

1.07

1.81

0

1

2

3

4

5

6

7

Under $15,000 $15,000-$50,000 $50,000+ Totals

Mod

e Sh

are

Perc

ent

2008

2001

1995

Transit Mode Share by Home Ownership Status

4.93

0.81

4.25

0.73

4.57

0.9

0

1

2

3

4

5

6

Renter Owner

Mod

e Sh

are

Perc

ent

2008

2001

1995

Transit Mode Share by Immigration Status

0.12 0.39 0.45 1.11 1.15

3.40

1.56

0.44 0.85 0.87

2.67

1.87

7.69

5.20

0

1

2

3

4

5

6

7

8

9

Outside MSA

Under 250 250-500 500-1,000 1,000-3,000 3,000+ All

Mod

e Sh

are

Perc

ent

Born in US Born Outside USA

Mode Speeds

29.1

13.7

10.1

8.7

11.5

11.2

11.2

10.1

10.8

10.9

10.3

11.8

0

5

10

15

20

25

30

35

40

Not in MSA or CMSA

MSA of Less than 250,000

MSA of 250,000 - 499,999

MSA of 500,000 - 999,999

MSA or CMSA of 1,000,000 - 2,999,999

MSA or CMSA of 3 million or more

Spee

d M

PH

Metro Area Size

2008 Transit 2008 POV 2001 Transit 2001 POV

Transit and Elderly Person Trips per Day by Age

Transit Mode Share by Age

Share of Transit Trips by Age Groups

0.0

1.0

2.0

3.0

4.0

5.0

5-14 15-24 25-34 35-44 45-54 55-64 65-74 75-84 85+

Ave

rage

Tri

ps p

er D

ay

Age Group

0.0% 0.5% 1.0% 1.5% 2.0% 2.5% 3.0% 3.5%

5-14 15-24 25-34 35-44 45-54 55-64 65-74 75-84 85+

Tran

sit M

ode

Shar

e

Age Group

5-14, 6.5%

15-24, 21.3%

25-64, 64.0%

65+, 8.2%

Distribution of Transit Trips by Wait Time for Selected Transit Markets

34.4

%

28.6

%

44.4

%

41.4

%

31.3

%

30.3

%

33.1

%

21.5

%

17.5

%

25.7

%

0%

20%

40%

60%

80%

100%

15+ minutes 10 - 14 minutes 5 - 9 minutes Under 5 minutes

Distribution of Transit Trips by Wait Time for Income-Based Markets

12.0% 18.5% 32.4% 32.2%

23.4%

31.1%

38.8% 34.0% 23.3%

26.4%

17.9% 21.3% 41.4%

24.0% 11.0% 12.4%

0%

20%

40%

60%

80%

100%

Under $15,000 (low-income)

$15,000-$49,999 (middle low-

income)

$50,000-$99,999 (middle high-

income)

$100,000+ (high-income)

15+ minutes 10 - 14 minutes 5 - 9 minutes Under 5 minutes

Distribution of Transit Trips by Last Access Mode for Income-Based Markets

94.2% 90.7% 88.0% 78.9%

3.9% 6.8% 5.4%

9.5%

0%

20%

40%

60%

80%

100%

Under $15,000 (low-income)

$15,000-$49,999 (middle low-income)

$50,000-$99,999 (middle high-income)

$100,000+ (high-income)

Other Bike POV Transit Walk

Cumulative Distance of Household to Bus Route

0%10%20%30%40%50%60%70%80%90%

100%

<= .1

5.3

1 - .

45.6

1 - .

75.9

1 - 1

.05

1.21

- 1.

351.

51 -

1.65

1.81

- 1.

952.

11 -

2.25

2.41

- 2.

552.

71 -

2.85

3.01

- 3.

153.

31 -

3.45

3.61

- 3.

753.

91 -

4.05

4.21

- 4.

354.

51 -

4.65

4.81

- 4.

954.

96 -

5.10

5.11

- 13

>13

- 21

>21

- 29

>29

- 37

>37

- 45

>45

- 52

>52

- 60

>60

- 68

>68

- 76

>76

- 84

>84

- 92

Per

cent

of H

ouse

hold

s

Distance in Miles (note scale break at 5.11 miles)

Almost 50 % of households nationally live within 1/2 mile of a bus route

Bus trip Mode Share by Household Distance

0%

1%

2%

3%

4%

5%

6%

7%

<= .15 .16 - .30 .31 - .45

Bus

Mod

e S

hare

Miles

Bus All TripsBus Work Trips

NHTS - A FIX FOR DATA ADDICTS AND INOCULATION AGAINST UNINFORMED DECISIONS

27