The grade (US) or gradient (UK) of a physical feature, landform or constructed line refers to the tangent of the angle of that surface to the horizontal. It is a special case of the slope, where zero indicates horizontality. A larger number indicates higher or steeper degree of "tilt". Often slope is calculated as a ratio of "rise" to "run", or as a fraction in which run is the horizontal distance and rise is the vertical distance.
25% ascent warning sign, Wales
30% descent warning sign, over 1500 m. La Route des Crêtes, Cassis, France
A trolleybus climbing an 18% grade in Seattle
Ascent of German Bundesstraße 10
A railway track or railroad track, also known as a train track or permanent way, is the structure on a railway or railroad consisting of the rails, fasteners, railroad ties and ballast, plus the underlying subgrade. It enables trains to move by providing a dependable surface for their wheels to roll upon. Early tracks were constructed with wooden or cast iron rails, and wooden or stone sleepers; since the 1870s, rails have almost universally been made from steel.
New railway concrete sleeper
Traditional railway track showing ballast, part of sleeper and fixing mechanisms
Track of Singapore LRT
Ballastless high-speed track in China