Glossary
| Term | Description |
|---|---|
| Acrylic material |
Binder material used in high friction surface treatment that holds the aggregate firmly to the pavement. |
| ADT | Average Daily Traffic – the traffic volume of a road measured in vehicles per day. |
| Advisory speed plaque | A sign that is placed below a Horizontal Alignment sign to advise motorists of the safe speed through the curve. |
| Ball bank indicator | An inclinometer that is used for determining safe curve speeds for horizontal curves. |
| Cable barrier |
A flexible barrier made from wire rope supported between frangible posts. |
| Calcined bauxite aggregate | A hard, coarse aggregate used in high friction surface treatment. |
| Clear Zone | The unobstructed traversable area provided beyond the edge of the through traveled way for the recovery of errant vehicles, as defined by AASHTO. |
| CMF | Crash Modification Factor – a multiplicative factor used to compute the expected number of crashes after implementing a countermeasure. |
| CMF Clearinghouse |
A website that provides the largest collection of CMFs for geometric design elements and traffic control devices available in the United States. |
| Compound curves | Two or more tangential, consecutive curves. |
| Curve Deliniation | Treatments that enhance the conspicuity of a curve (e.g., wider edge line, higher retroreflectivity of signs, postmounted delineators, chevrons, raised pavement markings). |
| Concrete safety shape |
A rigid barrier that does not deflect. |
| Delineators |
A device mounted above the roadway surface and along the side of the road in a series to indicate roadway alignment. |
| Epoxy material |
Binder material used in the application of high friction surface treatment that hold the aggregate firmly to the pavement. |
| FARS | Fatality Analysis Reporting System – a nationwide census providing annual data regarding fatal injuries in motor vehicle traffic crashes. |
| Guardrail | A semi-rigid barrier usually either a steel box beam or W-beam that deflect less than flexible barriers. |
| HFST | High Friction Surface Treatment – a thin layer of aggregate bonded to the pavement surface designed to increase friction and compensate for sharp curves. |
| Milled | Milled rumble strips are made by a machine with a rotary cutting head, creating a smooth, uniform, and consistent groove in the pavement. They cause tire noise and vehicle vibration when traversed. |
| MUTCD | Manual on Uniform Traffic Control Devices – defines the standards used by road managers nationwide to install and maintain traffic control devices on all public streets, highways, bikeways, and private roads open to public traffic. |
| Pavement grooving | A pavement countermeasure technique to apply longitudinal or transverse cuts onto the pavement surface to increase or restore pavement friction. |
| Pavement raveling | Deterioration of the pavement surface caused by aggregate particles becoming dislodged. |
| Retroreflective | A material or device that reflects light back to its source. |
| RSA | Road Safety Audit – a formal safety performance examination of an existing or future road or intersection by an independent, multidisciplinary team. |
| Safety EdgeSM | A paving technique used system-wide to improve pavement durability and reduce crashes by shaping and consolidating the pavement edge into a 30 degree wedge. |
| Superelevation | The banking of a horizontal curve. |
| Systemic approach | The analysis of crash data on a system-wide basis that considers identifying factors that indicate higher risks for severe crashes. |