BTS | Table 1 - Definitions of Variables Used

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BTS Home > Publications > Journal of Transportation and Statistics > Volume 3 Number 3 > Paper 3

Table 1
Definitions of Variables Used

			Mean*	SD*
Dependent variables	Annual VMT	Annual vehicle-miles traveled in vehicle, as estimated by household respondent.	11,040	8,230
	Number of person-trips	Number of person-trips in the vehicle on the survey day	7.11	6.2
	Number of recreational person-trips	Number of person-trips in the vehicle on the survey day for trips of recreational purpose (including social, shopping, and eating-out purposes)	2.2	3.06
	Trip occupancy: all purposes	Number of vehicle occupants during trip	1.84	1.1
	Trip occupancy: recreational purposes	Number of vehicle occupants during recreational trip (including social, shopping, and eating-out purposes)	1.71	0.99
	Vehicle type chosen for trip	Type of vehicle chosen by driver for trip (all purposes included)	NA	NA
	Newest vehicle owned	Type of newest-vehicle owned (identified by latest model year); includes passenger car, SUV, pickup, & minivan	NA	NA
Explanatory variables	Population density	Population density of census tract (persons per square mile)	3,858	5,306
	Income per household member	Annual household income (1995 US$) divided by household size (where income is taken to be middle of class range)	$19,075	$13,561
	Vehicle age	1996 minus model year of vehicle	6.02	4.96
	Household members per vehicle owned	Household size divided by vehicles owned by household	1.48	0.8
	LDT indicator	Equals one for SUVs, pickups & minivans (zero otherwise)	0.26	0.44
	SUV indicator	Equals one for SUVs (zero otherwise)	0.08	0.27
	Pickup indicator	Equals one for pickups (zero otherwise)	0.11	0.31
	Minivan indicator	Equals one for minivans (zero otherwise)	0.08	0.27
	Vehicle price/income	Average purchase price of new vehicle (based on 1997 sales data) divided by annual household income)	0.74	0.14
	Household size	Number of household members	2.83	1.31
	Number of vehicles already owned	Number of vehicles already owned by household, of that vehicle type	0.92	0.87
	Number of cars already owned	Number of passenger cars already owned by household	0.56	0.69
	Weekend day	Equals one for Saturday and Sunday trips (zero otherwise)	0.22	0.42
	Vehicle occupancy	Number of vehicle occupants (for model of vehicle-type choice)	1.58	0.99
	Trip length	Self-reported trip travel time (minutes)	14.21	13

*Note: Means and standard deviations (SDs) vary slightly in some cases, according to sample used/model applied

Table 1 Definitions of Variables Used

Table 1
Definitions of Variables Used