Modal share data is usually obtained by travel surveys, which are often conducted by local governments, using different methodologies. Sampling and interviewing techniques, definitions, the extent of geographical areas and other methodological differences can influence comparability. Most typical surveys refer to the main mode of transport used during trips to work. Surveys covering entire metropolitan areas are preferred over
city proper surveys which typically cover only the denser inner city. the reference years in these lists span over two decades, making comparisons problematic, especially given changing population, new transportation infrastructure and the effect of the
COVID-19 pandemic, among other factors. ==Modal split of journeys to work==