Glossaries

Definitions: S - U

Semi-Directional Interchange –  See Interchanges, Semi-Directional Interchange

Service Interchange – See Interchanges, Service Interchange.

Shoulder – The portion of the roadway contiguous with the traveled way for accommodation of stopped vehicles, for emergency use, and for lateral support of base and surface courses (NJDOT, 2006). 

Shoulder Rumble Strip – “A longitudinal design feature installed on a paved roadway shoulder near the travel lane. It is made of a series of indented or raised elements intended to alert inattentive drivers through vibration and sound that their vehicles have left the travel lane. On divided highways, they are typically installed on the median side of the roadway as well as on the outside (right) shoulder (FHWA, Roadway Shoulder Rumble Strips Technical Advisory Website http://www.fhwa.dot.gov/legsregs/directives/techadvs/t504035.htm, 2001)."

Sidewalk – The portion of a street between the curb lines, or the lateral lines of a railway, and the adjacent property lines, intended for use by pedestrians (Georgia Code and Rules 40-1-1).

Sight Distances – The length of roadway ahead visible to a driver.

Decision Sight Distance – Sight distance that allows a driver to determine and complete the most efficient maneuver in response to an unexpected condition

Intersection Sight Distance – Sight distance needed for decisions at complex locations such as intersections. Values are substantially greater than Stopping Sight Distance.

 

Passing Sight Distance – Sight distance needed for passing other vehicles (applicable only on two-way, two-lane highways at locations where passing lanes are not present).

Stopping Sight Distance - Sight distance needed for a driver to see an unexpected condition and stop the vehicle. At a minimum, Stopping Sight Distance is required at all locations on all roadways.

Sight Distance Triangle – Specified areas along intersection approach legs and across their included corners that should remain clear of obstructions (AASHTO Green Book, 2004).

 

Slope – The face of an embankment or cut section; any ground the surface of which makes an angle with the plane of the horizon. 

Speed Design – See Design Speed

Speed Zone – a section of highway with a speed limit that is established by law but which might be different from a legislatively specified statutory speed limit (FHWA MUTCD, 2003)

Spiral – See Curves: Transition Curve

Standard – Criteria having recognized and usually permanent values which are established formally as a model or requirement. 

Stopping Sight Distance –  See Sight Distances: Stopping Sight Distance.

Superelevation – The elevating of the outside edge of a curve to partially offset the centrifugal force generated when a vehicle rounds the curve. 

Superelevation Runoff –  “The length of roadway needed to accomplish a change in outside lane cross slope from zero (flat) to full superelevation, or vice versa  (AASHTO Green Book, 2004, p. 175)."

Superelevation (Tangent) Runout – The longitudinal distance required to transition between normal crown and 0% cross slope (or vice versa).

Superelevation Transition – “The superelevation runoff and tangent run out sections (AASHTO Green Book, 2004, p. 175)."

Sustained Grade – A continuous road grade of appreciable length and consistent, or nearly consistent, gradient.

Synchro – software application used for traffic analysis, specifically to optimize traffic signal timing and perform capacity analyses. The software supports the Universal Traffic Data Format (UTDF) for exchanging data with signal controller systems and other software packages.

System Interchange – See Interchanges, System Interchange

T Interchange - See Interchanges, Three-Leg Interchange

Traffic Characteristics – any characteristic of the traffic stream that may affect capacity, free-flow speed, or operations, including the percentage composition of the traffic stream by vehicle type and the familiarity of drivers with the freeway.

Traffic Control Device – A sign, signal, marking or other device placed on or adjacent to a street or highway by authority of a public body or official having jurisdiction to regulate, warn, or guide traffic.     

Traffic Lane  – See Lanes: Traffic Lane.

Transfer Road  – A road that connects core roadways and C-D roads

Transition – A section of variable pavement width required when changing from one width of traveled way to a greater or lesser width.

Transition Curve – See Curves: Transition Curve

Traveled Way – The portion of the roadway provided for the movement of vehicles, exclusive of shoulders, auxiliary lanes and bicycle lanes (NJDOT, 2006).

Truck Apron – The mountable portion of a roundabout central island that is drivable specifically provided to accommodate the path of the rear left wheels of larger vehicles.

Turn Lane – See Lanes: Turn Lane.

Turning Path – The path of a designated point on a vehicle making a specified turn.

Urban Area – “Places within boundaries set by the responsible State and local officials having a population of 5,000 or more (AASHTO Green Book, 2004)."

Urban Arterial – Functional classification for a street or highway that serves urbanized areas and provides the highest level of service at the greatest speed for the longest uninterrupted distance, with some degree of access control. 

Urban Collector –  A street or highway that provides both land access service and traffic circulation within residential neighborhoods, commercial or industrial areas. It differs from the arterial system in that facilities on a collector system may penetrate residential neighborhoods, distributing trips from the arterials through the area to the ultimate destination. Conversely, the collector street also collects traffic from local streets in residential neighborhoods and channels it into the arterial system (AASHTO Green Book, 2004).

Urban Roadway – A roadway that is classified functionally as an Urban Arterial, Urban Collector, or Urban Local Street that operates at speeds generally less than or equal to 45 mph and features curb and gutter.

Urban Shoulder – The part of an urban roadway beginning at the edge of travel and extending to the breakpoint of the fore slope or back slope that ties to the natural terrain.