Methods for Identifying High Collision Concentrations for Identifying Potential Safety Improvements: Development of Safety Performance Functions for California
(English)
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This research developed type 1 and type 2 safety performance functions (SPFs) for roadway segments, intersections and ramps on the entire Caltrans network. Type 1 SPFs involved statistical models with a length offset, and average daily traffic (ADT) while type 2 SPFs included geometrics as well. In the case of intersections, type 2 SPFs included traffic control, ADT and roadway geometrics. For ramps, type 2 SPFs included variables related to metering, HOV lane presence and ramp configuration. The research developed SPFs using data based on the period 2005-2010, and tested the SPFs on the period 2011-2012. Type 1 and type 2 SPFs were compared for predictive effectiveness, and it was found that type 2 SPFs provided for better measures of effectiveness such as mean absolute deviation, mean absolute percent error and mean squared error.
Methods for Identifying High Collision Concentrations for Identifying Potential Safety Improvements: Development of Safety Performance Functions for California