Sain’s Role in Alabama’s Horizontal Curve Safety Initiative

Posted by and on Apr 26, 2016

horizontal curveEach year between 800 and 900 people in Alabama die in traffic crashes.  Our goal as a state is to one day get to zero fatalities. That is a lofty goal, but when you consider the people you know and love, zero fatalities is the only acceptable standard.

The Alabama Department of Transportation has many strategic initiatives aimed at reducing highway crashes.  One of the newest initiatives is aimed at reducing crashes on horizontal curves.

A horizontal curve is a very important transition element in geometric design for highways. A horizontal curve provides a transition between two tangent strips of roadway, allowing a vehicle to negotiate a turn at a gradual rate rather than a sharp cut.

One crash type that is closely associated with horizontal curves is the single-vehicle roadway departure (run-off road) crash.  In Alabama, roadway departure crashes near a horizontal curve correlate to: 11% of total crashes, 22% of fatal crashes and 13% of injury crashes. Keeping in mind that horizontal curves represent a tiny percentage of total roadway mileage, they are over-represented in terms of crashes for the overall roadway. In a short span of only five years (2008-2012), 22,400 crashes occurred in the vicinity of a horizontal alignment change on the state system; 416 of those were fatal crashes and 6,351 involved injuries.  Frequently these crashes are due to driver behaviors, like driving too fast, driving while intoxicated, or when drowsy.  But sometimes the roadway or its environment can be altered to help drivers maintain control through horizontal curves and thus improve safety performance.

The Alabama DOT’s Office of Safety and Operations developed the Horizontal Curve Safety Initiative to address safety issues related to high crash frequency or patterns of roadway departure crashes on the state highway system. It is a strategic initiative designed to help lower the incidence of fatal and injury crashes in Alabama. Like many other states with large amounts of rural road miles, Alabama has a history of roadway departure crashes that is higher than the national average. If we can effect a lowering of crashes along horizontal curves in Alabama, we will see a reduction in deaths and injuries.

Sain Associates is one of two consulting firms assisting ALDOT with the Horizontal Curve Safety Initiative.  The project involves evaluating curvature, traffic signing and pavement marking at approximately 690 sites across Alabama. At each site, a team of engineers conducts a road safety assessment to identify treatments (called countermeasures) that can be installed to improve driver performance and reduce the incidence of traffic crashes. The countermeasures could include things like sign alterations or additions, installation of rumble strips, application of high-friction pavement surface, or shoulder widening, among other things. The emphasis is on low-cost, short-term improvements, but allowance is made for situations where more expensive long-term improvements are needed.

Our staff at Sain is especially excited to be part of the team with ALDOT on this project because it has such a tremendous potential to save lives.  This is the kind of project that many engineers consider a career high point because it has such significance. We are honored and humbled to have been chosen for the project.

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