7: MTC MNL Mode Choice, Diminishing OVTT by Distance¶

The primary shortcoming of the specification in Model 6 is that the estimated value of IVT is unrealistically small. At least two alternatives can be considered for getting an improved estimate of the value of out-of-vehicle time. One is to assume that the sensitivity of travelers to OVT diminishes with the trip distance. The idea behind this is that travelers are more willing to tolerate higher out-of-vehicle time for a long trip rather than for a short trip.

Model 7 ensures this result by including total travel time (the sum of in-vehicle and out-of-vehicle time) and out-of-vehicle time divided by distance in place of in- and out-of-vehicle travel time. (pp. 114)

d = larch.examples.MTC()
m = larch.Model(dataservice=d)
from larch.roles import P, X, PX
m.utility_co = P("ASC_SR2")  + P("hhinc#2,3") * X("hhinc")
m.utility_co = P("ASC_SR3P") + P("hhinc#2,3") * X("hhinc")
m.utility_co = P("ASC_TRAN") + P("hhinc#4") * X("hhinc")
m.utility_co = P("ASC_BIKE") + P("hhinc#5") * X("hhinc")
m.utility_co = P("ASC_WALK") + P("hhinc#6") * X("hhinc")

We diminish the effect of ovtt by dividing its parameter by distance.

m.utility_ca= (
+ PX("totcost")
+ P("motorized_time") * X("(altnum <= 4) * tottime")
+ P("nonmotorized_time") * X("(altnum > 4) * tottime")
+ P("motorized_ovtbydist") * X("(altnum <= 4) * ovtt/dist")
)
m.availability_var = '_avail_'
m.choice_ca_var = '_choice_'
m.ordering = (
("LOS", ".*cost.*", ".*time.*", ".*dist.*", ),
("Income", "hhinc.*", ),
("ASCs", "ASC.*", ),
)
>>> m.maximize_loglike()
┣ ...Optimization terminated successfully...
>>> m.calculate_parameter_covariance()
>>> m.loglike()
-3547.344...

>>> print(m.pfo()[['value','std err','t stat','robust std err','robust t stat']])
value    std err  t stat  robust std err  robust t stat
Category Parameter
LOS      totcost             -0.004  2.391e-04 -17.221       2.694e-04        -15.283
motorized_time      -0.042  3.516e-03 -11.815       3.780e-03        -10.990
nonmotorized_time   -0.047  5.496e-03  -8.636       5.355e-03         -8.863
motorized_ovtbydist -0.181  1.787e-02 -10.138       2.284e-02         -7.933
Income   hhinc#2,3           -0.001  1.383e-03  -0.995       1.481e-03         -0.929
hhinc#4             -0.007  1.914e-03  -3.787       1.884e-03         -3.848
hhinc#5             -0.012  5.244e-03  -2.261       6.300e-03         -1.882
hhinc#6             -0.008  3.188e-03  -2.583       3.530e-03         -2.333
ASCs     ASC_BIKE            -2.687  3.336e-01  -8.053       3.771e-01         -7.126
ASC_SR2             -2.188  9.763e-02 -22.416       1.058e-01        -20.692
ASC_SR3P            -3.518  1.229e-01 -28.615       1.272e-01        -27.662
ASC_TRAN            -0.042  1.597e-01  -0.266       1.659e-01         -0.256
ASC_WALK            -1.023  2.921e-01  -3.503       2.971e-01         -3.443