In order to estimate how some countermeasure or treatment might affect the safety of an entity (e.g., road location, intersection) if it were implemented it is necessary that we have the safety analysis and evaluation tools to: (1) Estimate what the expected number of consequences (fatality, injury and Property Damage Only collisions) would have been in the 'after' period had the treatment not been implemented, and (2) Compare these estimates with what the expected level of safety would be in the 'after' period if the treatment had been implemented. For example, in the case of un-signalized intersections, we would like to be able to measure how the safety of a particular un-signalized intersection would be changed, and by how much, if it were signalized. The capacity to measure this safety differential would provide the information needed in the decision-making process for determining whether the installation of a traffic signal is warranted (from a safety perspective) at a particular un-signalized intersection. This paper discusses a novel approach and new safety analysis and evaluation tools for measuring the safety of un-signalized and signalized intersections and comparing their relative levels of safety, as well as an objective, quantitative process for determining whether or not a traffic signal is warranted at an un-signalized intersection.
Abstract