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This paper proposes a method to allocate resources in power distribution planning and also introduces a new reliability index category, RT, flexibility to adjust to different laws or distribution system operator (DSO) policies of long outages. Possible legal consequences for distribution system operators are first identified and studied. A vulnerability-analysis method is introduced, including a statistical validation. The overall idea is to identify and evaluate possible states of power distribution systems using quantitative reliability analyses. Results should thus indicate how available resources (both human recourses and equipment) could be better utilized, e.g., in maintenance and holiday scheduling and in evaluating whether additional security should be deployed for certain forecasted weather conditions. To evaluate the method, an application study has been per- formed based on hourly weather measurements and about 65 000 detailed failure reports over eight years for two distribution systems in Sweden. Months, weekdays, and hours have been compared and the vulnerability of several weather phenomena in these areas has been evaluated. Of the weather phenomena studied, only heavy snowfall and strong winds, especially in combination, significantly affect the reliability. Temperature (frost), rain, and snow depth have a relatively low or no impact.impact.