Identifying traffic safety needs - a systematic approach : research report and user manual.

PDFTech ReportFHWA/IN/JTRP-2012/02SPR-3315Traffic safetyHighway safetyTransportation safetySafetySafety programsSafety factorsRisk assessmentSoftwareComputer programsIndianaPurdue University. Joint Transportation Research ProgramTarko, Andrew P.Azam, Shafiul MdThomaz, JoseRomero, MarioPurdue University. Joint Transportation Research ProgramIndiana. Dept. of TransportationUnited States. Federal Highway AdministrationNTL-SAFETY AND SECURITY-Highway SafetyUS Transportation CollectionThe Indiana Department of Transportation (INDOT) manages road safety in Indiana through safety emphasis areas, identification ofsafety needs within these areas, and development and implementation of transportation interventions that address the safetyneeds. Indiana applies system-wide performance screening to state roads using the somewhat limited, non-integrated toolsavailable to date. A site-specific countermeasure development and evaluation process (scoring) is being used to determine essentialproject intent and merit or cost-effectiveness. This projects addresses the need for a unifying approach to data-driven identificationof safety emphasis areas and safety improvement projects via a systematic evaluation of safety needs in the Indiana road network.Such a method must utilize a database that integrates the Indiana state network, traffic, road inventory, and crash data.A method for safety screening of state roads in Indiana was developed with the following screening tasks in mind: (1) Identificationof high crash locations (segments, intersection, ramps and bridges), corridors, and areas in terms of high crash frequency, crashrate, or proportion of a particular crash type. (2) Facilitate program-based screening (e.g., shoulder widening, median improvement,etc.). (3) Facilitate special programs and projects (e.g., five percent report)In order to ensure the versatility of screening tasks and the data maintenance, four components are included in the screening tool:(1) data management, (2) standard screening, (3) roads clustering and special studies, (4) results presentation. The datamanagement includes updating the existing data by utilizing renewable sources for data, reformatting the source data to meet thestandards of the master database, integrating these data into tables that meet certain specifications, and replacing the existingdata. The data management procedures include ArcGIS geo-processing and VBA-implemented and Model Builder codes that are notpackaged as a single module but which are used separately as needed to maintain flexibility of the data management process.A window-based user interface, query editor, facilitates selection of criteria for safety screening. To help the user build a query, theselection criteria have been grouped into four categories: geographical scope (state, county, etc.), element (segment, township,etc.), crash criteria, and road criteria. The query is translated to SQL and sent to the screening engine. The results include safetyperformance measures such as crash frequencies, rates, and proportion together with basic statistical indicators. Road segmentsand intersections that exhibit an excessive number of crashes may be concentrated along longer road sections. Clustering theseelements may reveal large scale safety issues that otherwise might be overlooked if the screening analysis is focus on individualspots. The geo-coded results can be sorted in a table or displayed on GIS maps with Google Earth or ArcGIS to visualize the spatialdistribution of the identified high-crash roads