Accessibility assessment of public transport systems is essential for ensuring that infrastructure remains inclusive for individuals with disabilities or mobility impairments. However, the sheer size of public transport networks poses a significant challenge for the physical observation and assessment of accessibility. This paper presents an efficient approach to the accessibility assessment of tram transport based on simulation within a digital twin environment. We propose a novel framework that integrates advanced data acquisition and processing steps, including mobile mapping of the tram routes, determination of the deployment zone of the mobility aid lift (MAL), and the assessment of tram accessibility by simulating the MAL deployment in the digital twin. We present a case study of three tram routes in Melbourne, Australia, which demonstrates that the digital twin provides a practical and reliable tool for assessing tram accessibility. Our results also highlight the potential of the proposed digital twin approach for assessing the accessibility of other modes of public transport, such as train networks and bus stations.