Multiple-Vehicle (Chain-Reaction) Accidents and Radar Signatures

Multiple vehicle “chain reaction” accidents occur at least a dozen or more times annually, causing dozens of fatalities and significant property damage. Indirect costs include lost productivity, emergency response overtime expenses, and hassles associated with closures of major highways. Additionally, motorists may be stranded for hours in often hazardous weather conditions.

While the cause of such accidents is generally driver error or mechanical failure, weather is often a contributing factor. Eyewitnesses report poor visibility and abrupt changes in weather conditions. Unfortunately, weather observation sites may be located miles away from the accident site, and observations of conditions themselves may be tens of minutes old. Radar, however, covers much of the country and low-level reflectivity returns can be used to estimate precipitation intensity and visibility. Complete volume scans are done in 10 minutes or fewer.

This study uses the Federal Accident Report System Database to assemble a list of chain-reaction accidents occurring from 2001 to 2012. Radar data from these accidents was then collected and analyzed to see if there was a correlation between precipitation intensity and chain-reaction accidents. Generally, there were increases in snow intensity immediately before such accidents. Other types of weather showed little to no change in radar returns prior to such accidents. Further evaluation of the usefulness of radar signatures in predicting possible chain-reaction accidents during snowstorms is recommended.