Empirical assessment of the impact of highway design exceptions on the frequency and severity of vehicle accidents

摘要

Compliance to standardized highway design criteria is considered essential toensure the roadway safety. However, for a variety of reasons, situations arisewhere exceptions to standard-design criteria are requested and accepted afterreview. This research explores the impact that design exceptions have on theaccident severity and accident frequency in Indiana. Data on accidents atroadway sites with and without design exceptions are used to estimateappropriate statistical models for the frequency and severity accidents atthese sites using some of the most recent statistical advances with mixingdistributions. The results of the modeling process show that presence ofapproved design exceptions has not had a statistically significant effect onthe average frequency or severity of accidents -- suggesting that currentprocedures for granting design exceptions have been sufficiently rigorous toavoid adverse safety impacts.