UNIT 1: Foundations of Road Safety

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State Departments of Transportation (DOTs) have many opportunities to improve safety-some of the most important opportunities arise in programs outside the traditional state safety engineering program. Addressing safety in multiple types of projects and programs creates a coordinated, Department-wide and statewide safety focus, saves lives, reduces injuries, and saves money.
The Interactive Highway Safety Design Model (IHSDM) is a suite of software analysis tools developed by Federal Highway Administration’s (FHWA) Office of Safety Research and Development to evaluate safety and operational effects of geometric design decisions on highways.
The American Association of State Highway and Transportation Officials’ (AASHTO’s) Highway Safety Manual (HSM) Part C Predictive Method (Chapters 10-12) estimates crash frequency and severity. The predictive method uses equations known as Safety Performance Functions (SPFs) to estimate the predicted average crash frequency as a function of traffic volume and roadway characteristics (e.g., number of lanes, median width, intersection control, etc.).