Getting to school on your own: the correlates of independence and modes of active school travel

Figures & data

Table 1. Descriptive statistics.

Variable	Measurment	n	Mean	S.D.	Min	Max
[Responses]
AST	Days of active travel (i.e., walking or biking) to or from school	367	3.51	4.26	0	10
IAST	Days of independent, active travel (i.e., walking or biking) to or from school	367	2.99	4.05	0	10
AST_W	Days of walking to or from school	367	2.35	3.63	0	10
AST_B	Days of biking to or from school	367	1.16	2.85	0	10
[Predictors]
BE_NEI	Neighborhood type (0 = suburban and 1 = new urbanism)*	367	0.31	0.46	0	1
BE_SCH	Distance to school along the circulation system (network distance, ratio)	367	1.71	1.76	0.00	15.05
BE_POP	Population of those aged 6–11 years in the census block	367	4.34	2.87	0.01	15.25
BE_MIX	Land use mix [0 = otherwise and 1 = if the neighborhood has at least one parcel (entirely or partially) with a retail, institutional, or office land use]*	367	0.27	0.44	0	1
BE_CON	Street connectivity (3-to-4 or 3-to-5-way intersections)	367	33.91	25.93	0	164
BE_SID	Sidewalk proportion (ratio of the sidewalk length per street length)	367	0.92	0.94	0	4
BE_DES	Physical activity locations (parks, greenway, trails, stream, pond, sports field, YMCA, school, shop, indoor sports facilities (martial arts, dance), cemetery, and bike lane	367	1.26	0.81	0	3
SD_AGE	Age (1 = 9 years, 2 = 10 years, and 3 = 11 years)	367	2.16	0.71	1	3
SD_FEM	Female (0 = male and 1 = female)*	367	0.49	0.50	0	1
SD_WHI	White (0 = others and 1 = White)*	367	0.55	0.50	0	1
SD_AUT	Automobiles in the household	367	2.23	1.17	0	9
SD_BMI85	BMI above the 85th percentile (0 = no and 1 = yes)*†	367	0.34	0.47	0	1
SD_PER	Parent’s permit to walk (let you walk anywhere without an adult?)*‡	367	0.32	0.47	0	1
SD_SIC	Sick last week (0 = no and 1 = yes)*‡	367	0.76	0.43	0	1
AT_1	Safe to walk (it is safe to walk or jog)	367	3.56	0.73	1	4
AT_2	Safe to bike (it is safe to ride a bike)	367	3.57	0.71	1	4
AT_3	Traffic (there is so much traffic that it makes it hard to walk)	367	1.35	0.71	1	4
AT_4	Crime (there is a lot of crime)	367	1.39	0.74	1	4
AT_5	See others (I often see other girls or boys playing outdoors)	367	3.23	1.00	1	4
AT_6	Street light (my neighborhood streets are well lit at night)	366	2.92	0.98	1	4
AT_7	Trees (there are trees along the streets)	367	3.29	0.96	1	4
AT_8	Interesting things (there are many interesting things to look at while walking)	367	3.01	0.96	1	4
AT_9	Sports equipment (at home there is enough sports equipment to use for physical activity)	367	3.26	0.96	1	4
AT_10	Sidewalk (there are sidewalks on most of the streets)	367	3.07	1.20	1	4
AT_11	Trails (there are bicycle or walking trails)	367	2.90	1.19	1	4
AT_12	Destinations (there are many places I like to go within easy walking distance of my home)	367	3.38	0.91	1	4
AT_13	Parents worry [my parents (or guardians) worry about something happening to me if I go somewhere on my own]	367	2.56	1.06	1	4
AT_14	Easy to walk to transit [it is easy to walk or bike to a transit stop (bus) from my home]	366	2.85	1.22	1	4
AT_15	People get along [people in this neighborhood generally get along with each other]	367	3.25	0.89	1	4
AT_16	Enjoy active travel to school [I enjoy (or would enjoy) walking or biking to school]	367	3.28	1.04	1	4
AT_17	Enjoy active travel to places [I enjoy (or would enjoy) walking or biking to places (park, playground, or shop)]	367	3.31	0.96	1	4
AT_18	Enjoy active travel without adults [I enjoy (or would enjoy) walking or biking to places without an adult]	367	2.93	1.06	1	4
AT_19	Active travel without adults is cool [other kids my age think walking or biking without an adult is “cool”]	367	2.86	0.98	1	4

* Binary variables

† BMI above 18.60 (19.08) for 9-year-old boys (girls), 19.36 (19.95) for 10-year-old boys (girls), and 20.16 (20.83) for 11-year-old boys (girls), which makes f (non-overweight) = 243 and f (overweight) = 124 (other typical percentiles such as 90th and 95th and BMI as a continuous variable were entirely insignificant)

‡ Inflation variables

Table 2. Count data models (n = 365).

	AST (model: ZIP)		IAST (model: ZIP)		AST_W (model: ZINB)		AST_B (model: NB)
	Coef.	S.E.	Coef.	S.E.	Coef.	S.E.	Coef.	S.E.
Neighborhood type (BE_NEI)†	−0.004	0.120	0.135	0.124	−0.368*	0.197	1.784**	0.682
Distance to school (BE_SCH)	0.018	0.032	0.033	0.033	−0.122*	0.064	0.055	0.116
Size of population aged 6–11 (BE_POP)	0.006	0.013	0.029**	0.013	−0.038*	0.021	−0.089	0.079
Land use mix (BE_MIX)†	0.152*	0.069	0.070	0.079	0.256**	0.106	−0.334	0.553
Street connectivity (BE_CON)	0.000	0.001	−0.001	0.001	0.003	0.003	0.005	0.011
Sidewalk proportion (BE_SID)	0.074**	0.044	0.081*	0.046	0.042	0.076	0.032	0.318
Physical activity locations (BE_DES)	−0.038	0.054	−0.013	0.059	−0.056	0.086	−0.155	0.331
Age (SD_AGE)	0.004	0.044	0.089*	0.051	0.001	0.068	0.062	0.302
Female (SD_FEM)†	−0.051	0.062	−0.148**	0.072	0.073	0.097	−1.287**	0.440
White (SD_WHI)†	0.025	0.071	0.081	0.081	−0.197*	0.108	1.533***	0.421
Automobiles (SD_AUT)	−0.017	0.028	0.019	0.030	0.008	0.038	−0.166	0.235
BMI above the 85th percentile (SD_BMI85)†	−0.124*	0.071	0.033	0.075	−0.007	0.113	−0.297	0.455
Parent’s permit to walk (SD_PER)†	−0.049	0.072	0.047	0.081	−0.081	0.113	−0.658	0.414
Sick last week (SD_SIC)†	0.030	0.074	0.020	0.082	0.135	0.115	0.289	0.502
Attitudes to physical settings (AT_F1)‡	0.023	0.048	−0.042	0.054	0.065	0.071	0.690**	0.330
Attitudes to subjective and safety settings (AT_F2)‡	−0.054	0.051	−0.130**	0.054	−0.080	0.076	0.290	0.324
Attitudes to positive utility (AT_F3)‡	0.095*	0.052	0.047	0.060	0.272**	0.091	0.279	0.287
(Constant)	1.922	0.170	1.377	0.201	1.968	0.258	−1.098	1.192
Inflate
Parent’s permit to walk (SD_PER)*	0.763***	0.236	1.026***	0.250	0.625**	0.250
Sick last week (SD_SIC)*	−0.408	0.255	−0.350	0.261	−0.116	0.266
(Constant)	0.231	0.226	0.331	0.231	0.397	0.238
Ln(α)					−2.5327	0.488	1.8881	0.171
α					0.0794	0.039	6.6070	1.132
LR χ^2 (17) Pseudo R^2 ML R^2 Cragg-Uhler R^2 Note:	26.19 (p = 0.071) 0.028 0.100 0.103 converged in 3 iterations		35.12 (p = 0.006) 0.043 0.137 0.142 converged in 3 iterations		34.67 (p = 0.007) 0.035 0.108 0.112 converged in 6 iterations		71.96 (p = 0.000) 0.096 0.179 0.205 converged in 4 iterations

† Binary

‡ Psychometric factors identified through common factor analysis in Table 3

* p < 0.1; ** p < 0.05; *** p < 0.001

Note: For variable descriptions, see Table 1.

Table 3. Common factor analysis.

	AT_F1 (physical settings)	AT_F2 (subjective and safety settings)	AT_F3 (positive utility)
Sidewalk (AT_10)	0.546	−0.033	0.248
Trails (AT_11)	0.509	0.089	0.224
Trees (AT_7)	0.473	0.142	−0.007
Street light (AT_6)	0.467	0.128	−0.049
Interesting things (AT_8)	0.442	0.147	0.052
Sports equipment (AT_9)	0.384	0.196	0.156
See others (AT_5)	0.382	0.066	0.276
Destinations (AT_12)	0.341	0.140	0.322
Safe to walk (AT_1)	0.365	0.714	0.079
Safe to bike (AT_2)	0.299	0.670	0.172
People get along (AT_15)	0.307	0.493	0.019
Crime (AT_4)	0.016	−0.449	−0.037
Traffic (AT_3)	−0.070	−0.384	−0.116
Parents worry (AT_13)	−0.047	−0.363	−0.139
Enjoy active travel to places (AT_17)	0.154	0.195	0.664
Enjoy active travel to school (AT_16)	0.216	0.150	0.613
Enjoy active travel without adults (AT_18)	0.040	0.255	0.566
Active travel without adults is cool (AT_19)	−0.001	−0.004	0.363
Easy to walk to transit (AT_14)	0.254	0.050	0.305
Eigenvalues	2.066	1.940	1.754

Note: Converged in 6 iterations

Appendix A. T-test of B.E. variables by neighborhood type.

	Conventional		New Urbanist		t	df	p
	M	SD	M	SD
Distance to school (BE_SCH)	2.16	1.88	0.72	0.86	10.1	365	.000
Size of population aged 6–11 (BE_POP)	4.52	3.27	3.92	1.55	2.4	364	.017
Land use mix (BE_MIX)	0.15	0.36	0.52	0.50	−7.0	166	.000
Street connectivity (BE_CON)	20.72	11.67	63.54	24.71	−17.6	135	.000
Sidewalk proportion (BE_SID)	0.43	0.44	2.01	0.85	−18.6	139	.000
Physical activity locations (BE_DES)	0.94	0.64	1.97	0.67	−13.7	206	.000

Appendix B. Fit of alternative models.

Models	Tests
Overall active school travel (AST_A)	Vuong test (Poisson vs. ZIP)	z = 7.02 (p = 0.0000)
	Vuong test (NB vs. ZINB)	z = 1.80 (p = 0.0356)
	Likelihood-ratio test (ZIP vs. ZINB)	χ-bar2 (1) = 5.4e-05 (p = 0.4971)
		Poisson	NB	ZIP	ZINB
	Log-likelihood	−1,018.400	−746.726	−662.307	−662.307
	AIC	5.679	4.196	3.744	3.750
	BIC	−10.464	−547.912	−704.950	−699.050
Independent active school travel (IAST_A)	Vuong test (Poisson vs. ZIP)	z = 6.95 (p = 0.0000)
	Vuong test (NB vs. ZINB)	z = 0.25 (p = 0.4007)
	Likelihood-ratio test (ZIP vs. ZINB)	χ-bar2 (1) = 1.2e-05 (p = 0.4986)
		Poisson	NB	ZIP	ZINB
	Log-likelihood	−950.448	−670.138	−601.870	−601.870
	AIC	5.307	3.776	3.413	3.418
	BIC	−146.369	−701.088	−825.825	−819.925
Walking active school travel (AST_W)	Vuong test (Poisson vs. ZIP)	z = 7.43 (p = 0.0000)
	Vuong test (NB vs. ZINB)	z = 3.46 (p = 0.0003)
	Likelihood-ratio test (ZIP vs. ZINB)	χ-bar2 (1) = 7.31 (p = 0.0034)
		Poisson	NB	ZIP	ZINB
	Log-likelihood	−928.207	−604.838	−569.686	−566.033
	AIC	5.185	3.418	3.237	3.222
	BIC	−190.851	−831.688	−890.192	−891.600
Biking active school travel (AST_B)	Vuong test (Poisson vs. ZIP)	z = 5.44 (p = 0.0000)
	Vuong test (NB vs. ZINB)	z = 0.25 (p = 0.3995)
	Likelihood-ratio test (Poisson vs. NB)	χ-bar2 (1) = 546.50 (p = 0.000)*
		Poisson	NB	ZIP	ZINB
	Log-likelihood	−613.297	−340.046	−338.926	−337.540
	AIC	3.459	1.967	1.972	1.970
	BIC	−820.670	−1,361.272	−1,351.713	−1,348.584

* Deviance goodness-of-fit = 991.1902 [p > χ2(347) = 0.0000] and Pearson goodness-of-fit = 1,952.528 [p > χ2(347) = 0.0000] also support NB.