Numerous Low Emission Zones (LEZs) have been implemented across Europe to improve air quality and reduce car use. However, to date, the impact of LEZs has been widely perceived as regressive, since vehicles that meet the low emission requirements are more expensive than others. The literature assessing the impact of LEZs on vulnerable and poor households prior to their implementation is sparse, particularly if we take into account the diversity of households’ capacities to adapt according to their characteristics and mobility habits, beyond the sole solution of purchasing a LEZ-compatible vehicle. However, such assessments would make it possible to define accompanying policies to improve the social justice of the LEZs. In this article, we develop a methodology to evaluate the ex-ante impacts of a LEZ on vulnerable or poor households. First, we identify households affected by the LEZ. Second, the VulMob multidimensional indicator is used to identify, among affected households, households with low transport-affordability and highly vulnerable households according to their vulnerability profiles. Third, we assess the adaptive capacity in terms of modal shift options and considering the possibility to modify the destination. We apply this methodology to the Grenoble area (France), using the Local Household Travel Survey. The results show that not only are highly vulnerable households more affected by the LEZ than other households, but also that more of them are left with no alternative but to buy a LEZ-compliant car. Nevertheless, modal shift seems an adaptation solution with great potential for all households. This could improve the environmental and health performance of LEZs. This work can guide decision-makers in the definition of preventive and compensatory policies, considering the profiles of transport vulnerability and the specificities of the territory.