based trips (86 percent) than among home-based trips (14 percent), while three-quarters were round trips. The values are similar for the metropolitan region as a whole and for Bogotá.

The INDEC survey data, which indicates an increase in e-commerce adoption in 2011-2018 in CABA (from 16.9 percent to 31.4 percent) and the province of Buenos Aires (from 5.9 percent to 15.9 percent), allows identifying whether this growth translated into a reduction in the number of trips for shopping purposes. In 2018, shopping trips in AMBA accounted for 13 percent of all trips and 12.1 percent of all home-based trips. About 96 percent of all shopping trips in 2018 were home-based, which is significantly higher than in Bogota; however, this figure is again subject to the caveat that the share home-based trips in surveys tend to be overestimated. Shopping trip generation rates increased between 2011 and 2018, from 1.74 to 1.84 trips per person, suggesting that at the aggregate level there was no trip substitution (reduction) due to the growth of e-commerce.

As already noted, the potential for trip reduction by e-commerce depends on the proportion of trips for shopping purposes that are part of trip chains. If people make trips to retail outlets to and from their homes, a virtualization of shopping would lead to a reduction of two trips. Conversely, if people shop as an intermediate activity between work and home, the shift from physical shopping to the Internet would lead to a reduction of one trip instead of two trips. Moreover, if the retail outlet is already located on the route between work and home and the trip is made by car, the impact of eliminating the intermediate activity on road traffic and its externalities will be small (the number of kilometers traveled is maintained).

The total trip reduction potential as a result of e-commerce in Bogotá in 2019 on a typical working day was 9.1 percent, since a total virtualization of commercial activity would lead to a 100 percent reduction of the round trips with a shopping purpose (7.9 percent of trips) but only one of the two trips with origin or destination to shopping activities in the case of trip chains (modifying the origin or destination of the other trips in the chain, avoiding the stop at the commercial establishment), which could lead to a 1.2 percent reduction of trips. In Buenos Aires, about 7 percent of trips with a shopping purpose were part of a trip chain in 2018, the share being much higher among non-home-based trips (93 percent) than among home-based trips (3.7 percent). Thus, the total trip reduction potential due to e-commerce in Buenos Aires on weekdays was 11.7 percent (assuming a full elimination of round-trip trips to or from a shopping activity and elimination of one of the two trips with origin or destination to shopping activities in trip chains).

Trips for shopping purposes in both cities have a somewhat higher weight in the higher income groups, but with a higher proportion of linked trips (especially in Bogota), which makes the potential for mobility reduction similar for all groups. In Bogota, the percentage of total trips for shopping purpose peaks in stratum 6 (11.7 percent), but so does the proportion of linked trips out of total trips for this purpose (41.6 percent, compared to 24 percent for the population as a whole). Stratum 2, which is the most populated, has the lowest mobility reduction potential (8.8 percent). In Buenos Aires, trips for shopping purposes in 2018 had a relatively homogeneous share across all income groups although with a positive correlation. The potential for trip reduction in 2018 ranged from 10.9 percent among the lowest income quintile to 12.4 percent among the highest quintile.

The potential for reduction in inter-peak hours is considerable but at peak hours is very small in either Bogota or Buenos Aires, especially in the morning peak hour (in Bogota, 3.7 percent, compared to 9.1 percent for the day as a whole, and in Buenos Aires, 0.7 percent, compared to 11.7 in the day overall). Trips for shopping purposes reach the highest weight in overall mobility in the morning at 10:00 (after the morning peak hours), at 28 percent in Bogota and 42 percent in Buenos Aires (Figure 2). At this time, up to 26.1 percent of trips in Bogota and up to 41.3 percent in Buenos Aires could be avoided by e-commerce according to the analysis of the household mobility surveys of 2019 and 2018, respectively. In the late afternoon, a new peak is recorded in both cities, but it is about half the intensity as in the morning. The share of linked trips (part of trip chains) in Bogota is much higher in the evening hours than in the morning, but this is not the case in Buenos Aires.

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