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price-inelastic, the model readily produces access value estimates of approximately $360
per trip for Point Reyes and $79 per trip for Monterey. Several characteristics of demand
that differ between the two sites suggest that this difference in per-trip values is plausible.
Several directions for further work are suggested by these results. It may be
possible to estimate a more flexible individual-specific normalized value of time within
the model, consistent with the two-constraint choice requirements. Using a count rather
than continuous demand error may improve the estimates further, though the available
count data estimators for systems of more than two goods are somewhat inflexible with
respect to the cross-equation covariances. Finally, it may also be possible to further
improve the flexibility of the demand model itself through the introduction of additional
parameters, though this may come at the cost of greater difficulty in using the model to
evaluate access values analytically or in finding global maxima of the likelihood
function.