Few studies have modeled the effects of policy measures on population exposure. This work assessed for the first time the impact of a policy measure on population exposure to nitrogen dioxide (NO 2) by using the activity-based model ALBATROSS. Activity-based models can be of great value in evaluating the effect of integrated policies and measures that have no obvious relation with transport or air quality. The scenario considered in this study involved changing the hours during which shops could be open to allow shopping earlier in the morning and later in the evening. Both emissions and population distribution of this policy measure could be derived from the activity travel behavior predicted by the activity-based model. It was found that extending the opening hours changed the activity pattern of the adult population in the Netherlands. Approximately 6% more nondaily and 0.5% more daily shopping hours were predicted. The change in activity pattern resulted in more transport (+0.5% more vehicle kilometers driven). As a consequence of this, emissions and air pollutant concentrations were also altered. When the concentration maps were matched with the dynamic population, an increase in population exposure to NO 2 was observed. Absolute differences were small (up to 0.40 μg/m 3). On an average weekday, NO 2 exposure increased by 0.15 μg/m 3. The relative change in exposure on an average weekday was 0.4%. In certain neighborhoods and at certain hours a more substantial increase could be observed.