Towards accessibility planning by means of GIS A case study on the access to potential job opportunities by three transport modes Autumn 2000

Over the last decades our global society has been highly influenced by automobility planning. Growing mobility has been seen as an indication of a well-functioning transport system and a society with increasing welfare. Excessive mobility can at the same time lead to urban sprawl, longer travel distances and travel times as well as other problems that can be associated with lower welfare. A planning policy more focused on accessibility, i.e. siting new locations of activities that can be easily reached by other transport means than car, can reduce the size of some of the transport problems. The concept of accessibility should therefore gain more attention since it is believed that it cannot have a negative connotation. So far it has been difficult to measure accessibility in the right way. Some indicators are so over-simplified that they are misguiding, others are so complex that they are difficult to grasp. Geographical Information Systems (GIS) provide a favourable working environment since transport data are spatial in nature. The first aim of the study is to measure accessibility between home and work by comparing the transport modes car, bicycle and public transport in Växjö city, Sweden. GIS is used throughout the analysis. A second aim is to discuss if the results can be used in the municipal planning process. Thirdly, the question of costs involved in this analysis are discussed. Approximately 150 irregular areas, so called statistical districts, within the city border are investigated. Digital road networks are used for all the three transport modes car, bicycle and public transport. A model based on street types determines the travel speeds by car. The bicycle speed is set to 17 km/h. The bus speeds are determined by travel time, walk time and transfer time. The accessibility is a measure of the number of job opportunities that can be reached from each residential area within a certain amount of time. The definition of a job opportunity is a place of employment, vacant or not, in a company. Most results are maps showing either the general accessibility for the different transport modes or a more focused analysis of one residential or commercial area. The results indicate that the accessibility to job opportunities by bus in Växjö is relatively low compared to bicycle and car. This is a result of long walking and waiting times as well as long transfer times. The bus frequency is also of great importance. Bicycle, on the other hand, has a very high accessibility compared to the car as long as the commuting distance is below 5 km. However, this requires well-maintained bicycle paths and a dense network. A quantification of this quality measure, the AT50 (Accessibility Time at 50%), which shows the time it takes to reach 50% of the job opportunities, is proposed. This measure has a potential of being a quantitative environmental indicator. The maps can be used both for visualisation of the present situation and to present planning alternatives and simulations. Environmental Impact Analyses, EIAs, can also gain from simulations of accessibility. In conclusion, these accessibility measures are a step in the right direction. Further studies are needed to verify the results as well as the presentation of maps and measures. Eventually, this will hopefully lead to practical tools that can be used in urban planning.