<p>Promoting higher density and implementing mixed land use have long been acknowledged as potentially effective land use based solutions to transportation problems. However, the policy has leaned toward mobility-based solutions, favouring rapid travel instead of high proximity. This tendency seems now to be reversing with the increasing popularity of the 15-minute city. This paper assesses the effectiveness of the 15-minute city in promoting sustainable travel in the Lisbon Metropolitan Area. Our research shows that the 15-minute city increases non-motorized travel among its residents by facilitating engagement with amenities such as supermarkets or green urban areas. Nevertheless, central and dense areas that are not necessarily 15-minute cities also contribute towards more sustainable travel, being more effective at reducing car travel due to increased public transit use. The 15-minute city impact on CO₂ emissions per household is higher than that of central and dense areas since non-motorized travel is presented as a direct alternative to car and transit, while central and dense areas also rely on transit as an alternative to car. Hence, policies combining proximity and density may eventually maximize the benefits of implementing land use based solutions by increasing non-motorized travel and the use of transit and reducing car travel and CO₂ emissions.</p>