1 Materiales tradicionales: La quincha

Among higher-wealth households, access to the BRT trunk system is associated with a significant drop in the likelihood of vehicle ownership, compared to households without trunk access. The strength of that relationship declines with distance, and levels off between 400m and 500m from a trunk stop. This finding suggests trunk access may well be enabling higher-wealth (choice) households to forgo or delay vehicle ownership within a fairly narrow corridor. The distance model lends support to the conclusion that the relationship between inner-ring trunk access and vehicle ownership in the first model is not simply an artifact of the more supportive urban form patterns present within 400m of the trunk lines.

None of the urban form variables is associated with vehicle ownership in higher-wealth households. This may be an indication that urban form does not influence vehicle ownership decisions among higher-wealth households. The distance model lends support to the conclusion that the relationship between inner-ring trunk access and vehicle ownership in the first model is

15 _{The predicted probability plot with respect to access to the trunk system, as the urban form} measures proximity and density vary across their ranges, looks nearly identical to the feeder access plots in Figure 12.

not simply an artifact of the more supportive urban form patterns present within 400m of the trunk lines (with respect to support for nonmotorized mobility, proximity to destinations, and bikeway access). Alternatively, given the overall high levels of urban form (with respect to support for nonmotorized travel, proximity to destinations, and bikeway access) present in the trunk service areas, the lack of a relationship between urban form and vehicle ownership may be a sign that the trunk area urban form already meets a supportiveness threshold, above which any improvements in urban form will not yield further benefits for higher-wealth households. On the other hand, as mentioned previously, the reduction of the urban form data into factor-analytic measures may be masking some of the variability in urban form along the trunk corridors. This suggests the need for a follow-up study using the actual urban form variables, rather than the factor-analytic ones.

Among lower-wealth households, the positive relationship between feeder access and vehicle ownership in the base model, combined with the lack of significance of distance to the closest feeder stop and a lack of sensitivity to implementation phase, suggests that some unobserved event concomitant and co-located with the introduction of the feeder service, rather than the feeder service itself, influenced lower-wealth households to motorize. For example, paving and other improvements to the street network were necessary in many areas before the introduction of feeder service; these roadway improvements may have increased the appeal of personal vehicle ownership. Similarly, a concurrent policy of providing or improving pedestrian infrastructure and other amenities in TransMilenio-served neighborhoods may have contributed to a heightened sense of well-being among lower-wealth households, which may in turn translate to greater psycho-social pressures to be motorized. Alternatively, reductions in congestion due to reorganization and relocation of conventional transit operators outside of the feeder service areas may have improved the desirability of driving and/or resulted in a lower level of transit service for households relying heavily on the conventional system.

This unexpected finding, particularly in contrast with the negative impact on vehicle ownership seen in the trunk area, may also be due in part to differences in the levels of service introduced by Transmilenio in the trunk versus feeder areas vis-à-vis the previous level of service provided by the conventional transit operators. Recall that prior to Transmilenio, transit service in the areas along what would become the trunk corridors was characterized by an oversupply of buses engaged in fierce competition for passengers, resulting in extreme congestion with average peak travel speeds of around ten kilometers per hour (Echeverry et al., 2005). Upon completion of Transmilenio’s first phase, average travel times for transit trips originating in the higher-wealth trunk area decreased by twelve minutes. In the feeder areas however, where competition and congestion had been present, but less extreme, average transit times actually increased by two minutes (Lleras, 2003). Thus, Transmilenio appears to have brought about improvements in travel times for wealthier households, for whom travel time is expected to be a key determinant of transit ridership, but not necessarily for poorer households.

Regardless of the cause of the uptick in motorization in feeder-served areas, however, it appears to be overcome by supportive urban form, at least for households located within 400m of a feeder stop. Inner ring access to the feeder service, when supported by good proximity to destinations and support for nonmotorized accessibility, results in a decrease in the likelihood of vehicle ownership, beyond what would be expected from supportive urban form in areas without feeder service. Furthermore, while trunk access appeared to be irrelevant to vehicle ownership decisions for lower-wealth households in the first analysis, there is strong evidence that, like for the feeder service, when trunk service is supported through urban form, it is associated with a decrease in vehicle ownership among lower-wealth households located within 400m of a trunk stop.