High budget transport infrastructure projects in the Istanbul Metropolitan Area endeavour to increase the efficiency of the transportation system. Among those investments; the bus rapid transit system - Istanbul Metrobus Line (IML) - is the most popular one that serves one million trips per day. Yet, the performance and impact of IML are not quantitatively assessed. Hence in this study, a high-resolution GIS-remote sensing framework is designed to analyse before and after accessibility over the period of 40 years (namely 1987-1997-2007-2014). High resolution satellite images were processed to generate the lacking historical land cover/use information with the expected high accuracy. Within the study area, utilized accessibility indices have unevenly increased after the operation of IML, such as 104.19% in potential and 99.07% in daily accessibility. According to the achieved results, such high spatio-temporal spatial framework could aid decision makers to quantitatively assess and evaluate the performance of such investments.