Palveluiden saavutettavuuden muutos pitkällä aikavälillä : Tapaustutkimuksena pääkaupunkiseudun kirjastoverkko

The formation of urban structure is a complicated process and its outcome, that cannot be easily forecast, is not necessarily optimal. This creates a need to understand the process and gives a reason to control it by urban planning. As the circumstances are in constant change, the plans have to anticipate the time to come – partly far into the future. Research is needed to support planning to understand the factors that affect the urban structure better. Accessibility, that seems to be one of the key factors in the processes of land use change, seems to provide a suitable tool for planning and research: when suitably defined, it can connect the properties of transport and land use systems as well as the economic, social and environmental goals. The availability of services is closely connected to the quality of living environment, so studying the accessibility of them can produce new notable information for the needs of urban planning. The aim of this study was to explain how changes in urban structure cause changes in the accessibility of services by walking, mass transit and car in the long term, and study how these changes could affect the use of the services both from the perspectives of the users' possibilities and the potential the services produce. The public library network in Helsinki region was studied as an example. Studying the accessibility of public libraries is useful as such, as they provide many types of positive impacts, but public libraries are also a convenient example in studying the accessibility of services as they are a service actively used in everyday life and information about the use is available. Distances in the accessibility measures were measured as travel time. Accessibility was measured both in travel times to the nearest library and in potentials of making a library trip calculated by library trip forecasting models based on the real behaviour of their users. Comparison was made between the years 2014 and 2050, during which the population and the transport system are expected to change as in the created scenarios, which are based on the new Helsinki City Plan. In addition, the possible effects to the accessibility of the public libraries by possible cost cuts in the service network were inspected by simulating the effects of the cuts. Based on the results the public libraries in the study area seem to be relatively well accessible by all the inspected transport modes. The changes in the transport systems seem to have minor effects on the accessibility when measured in travel time to the nearest library, but when the effects are measured in the potentials of making a library trip, they seem to be a bit more significant – by mass transit, accessibility would improve and by car, it would deteriorate. The forecast change in the population would increase the number of people accessing the nearest library in half an hour, but the proportion of this group to the total population in the area would be smaller than before. The attraction of libraries affect to the potentials they produce, but the impacts are concentrated on the surrounding areas of the libraries and on the traffic routes, where the accessibility is relatively good to begin with. Even though excluding some of the smallest libraries from the service network would have relatively small effects on the accessibility in the aggregate, the effects on individual level and for sustainable accessibility could be significant. Based on the study results more significant than the changes in the transport system or in the attraction of the services seem to be how near population and services are located each other: the prerequisites for multimodal accessibility cannot necessarily be guaranteed if the distances are long. Based on the study results, to prevent the deterioration of the preconditions of the goals of Finnish regional planning and the qualifications for sustainable accessibility due to the forecast population change – in other words to keep the current standard of service – some changes in the service network would be needed. However, as there was only one type of service inspected in this study and as there is uncertainty if the scenarios will happen in the future, the conclusions that can be drawn from the results are restricted. Still, studying the accessibility of a single service is useful as such as the needs for different type of services are different, and if it will give some hints of the future accessibility of services in general at the same time, even though just in a few scenarios, it can be easier to be prepared for the future.