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Table 2 Independent variables used in generalized additive models
Variable | Description |
|---|---|
\({\text {Yr}}\) | Categorical variable with a category for each year from 2006 to 2017 to capture long term temporal changes in crash probability due to external factors like improved safety features of vehicles. |
\(p_a\) | Probability of at least one occurrence of a specific crash type within a one hour time interval in a certain district with an average crash probability \(\bar{p}_{a,d}\). |
\(\bar{p}_{a,d}\) | Average hourly crash probability in an administrative district. |
\({\text {Trf}}\) | Average hourly traffic volume of the five traffic measurement stations closest to the district centre. Traffic volume is rescaled, so that 0 and 1 correspond to the average daily minimum and maximum traffic volume at a traffic station, respectively. |
\({\text {Wnd}}\) | Hourly maximum wind gusts, averaged over all ERA5 grid cells within disctrict boundaries. |
\({\text {Tmp}}\) | Hourly surface temperatures, averaged over all ERA5 grid cells within disctrict boundaries. |
\({\text {Prc}}\) | Hourly precipitation sum, averaged over all RADOLAN grid cells within disctrict boundaries. |
\({\text {Cld}}\) | Hourly total cloud cover, averaged over all ERA5 grid cells within disctrict boundaries. |
\({\text {Elv}}\) | Angle of sun elevation above the horizon, where positive and negative values correspond to the sun beeing located above and below the horizon, respectively. |