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[[File:Decay function.png|thumb|A decay function showing the change in weighted values for different modes and destination as travel time increases<ref>"Operationalizing Accessibility: Tools and Practices." State Smart Transportation Initiative. 30 March 2017.</ref>]]
Decay functions offer a more fine-tuned assessment of accessibility by weighting destinations based on how far away they are. A job that is five 5 minutes away contributes more to accessibility than one that is thirty 30 minutes away, and a job that is thirty 30 minutes away contributes about the same as one that is thirty-one 31 minutes away. Decay functions usually have a cut-off, somewhere around the 60 to 90 minute mark, where destinations are considered so inaccessible that they can no longer greatly contributeto accessibility at all.Using decay is challenging for a number of reasons. A meaningful and reliable decay function has to be developed. The computation computational effort of calculating the exact distance travel time to each location and weighting the location is large intense and complicatedoften slow. Finally, because locations are weighted, the final output is unit-less; it cannot be explained as the number of jobs within a 30 minute travel timewindow. This may allow for internal comparisons but may be difficult to convey conceptually at public presentations. One solution to improve presentation is developing to develop a clear scale and creating to create references as explanations for various points on the scale. (ex. a 1-100, where 80-100 is considered "excellent accessibility", etc.)
==First and Last Mile==
Bureaucrats, engaged

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