Bureau of Transportation Statistics (BTS)

Table 4a
Ordered Probit Model for Trip Occupancy: All Trip Purposes

Dependent variable: trip occupancy (all purposes) Beta SE t-stat P-value
Constant –0.565 0.007 –79.90 0.000
HH members per vehicle owned 0.340 0.002 153.00 0.000
Income per household member –1.06E-05 2.05E-07 –51.50 0.000
Population density –8.79E-06 4.27E-07 –20.60 0.000
Weekend day indicator 0.474 0.005 91.20 0.000
SUV indicator 0.174 0.008 20.90 0.000
Pickup indicator –0.229 0.008 –30.40 0.000
Minivan indicator 0.500 0.006 78.80 0.000
Shopping indicator 0.021 0.006 3.21 0.001
Eat out indicator 0.544 0.011 49.20 0.000
μo 0.000 na na na
μ1 0.875 0.003 302.00 0.000
μ2 1.431 0.004 365.00 0.000
μ3 2.039 0.006 368.00 0.000

Note: Trip occupancy is grouped into 1, 2, 3, 4, and 5+ person levels.

Log-likelihood function  
Constant only –324471.0
Convergence –298694.3
Pseudo-R2 0.079

Number of observations: 263,031 trips
Model form: Pr(Occupancy = 1) = Pr(μ* ≤ μo), Pr(Occupancy = 2) = Pr(μo ≤ μ* ≤ m1), Pr(Occupancy = 3) = Pr(μ1 ≤ μ* ≤ μ2), Pr(Occupancy = 4) = Pr(μ2 ≤ μ* ≤ μ3), and Pr(Occupancy ≥ 5) = Pr(μ3 ≤ μ*), where μ* = β′X + ε, and ε ~ Normal(0, 1)

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