HORIZONTAL ALIGNMENT - The twist and turns that the road makes is composed of 3 parts: TANGENTS. SPIRALS and CIRCULAR CURVES.

TANGENTS - The straight portion of the road.

SPIRAL - The transitional curves. These are curves with constantly changing radius used to transition between the tangent and circular curve.

CIRCULAR CURVE - The portion of the curve that has a constant radius.

VERTICAL ALIGNMENT - The ups and downs of the road and is composed of two parts: GRADES and VERTICAL CURVES.

GRADES - The straight portion of the ups and downs of the road. They are expressed in %. A 5% grade is a length of road that raises 5 feet in 100 feet. Grades are positive when climbing and negative when descending.

VERTICAL CURVES - The parabolic curves that are used to connect tow consecutive grades. This is called CREST when they are in the top and SAG when they are in the bottom.

HIGHWAY DRAWING - Drawing prepared by engineers for the construction of the road. The top part of the drawing usually contains the HORIZONTAL ALIGNMENT and is called the PLAN. The bottom part of the drawing contains the VERTICAL ALIGNMENT and is called the PROFILE.

PLAN - Is produced as a scale that varies in accordance with the importance of the road. Usually the scale varies between 1"=20' to 1=100'. This represents that one inch on the paper represents twenty or one hundred feet on the ground. This plan contains information such as: radius of the curves, length of the spirals and tangents, degree of deflection of the curves (how much the curve turns), road Stationing, Unite of the right of way, drainage to be installed, type of guide rait on location, etc.

STATIONING - A way of designating distance. Station 0+00 is the beginning of the road. Station 2+00 is 200 feet further along the line. Stationing usually runs from left to right of the drawing.

PROFILE - Profiles are produced at a horizontal scale that matches that of the plan and is drafted on the bottom part of the drawing. The profile is a longitudinal section of the road which represents what a cut along the center of the road looks like if you took a knife and cut the earth away. The profile contains two major parts, the Vertical Alignment and the Original Ground.

VERTICAL ALIGNMENT - Previously discussed, is drafted horizontally at the same scale as the plan but is usually exaggerated 10 times for the vertical scale. Therefore, if you have a horizontal alignment of r=100', the vertical scale will be 1"=10' and so on. This is done to add clarity to the drawing and allow more vertical detail to be shown.

EXISTING GROUND - Is the elevation representation of the ups and downs of the original ground before the road was built along the line represented by the Horizontal Alignment.

CROSS-SECTION - A view of the road taken perpendicular to the horizontal alignment. The major components are TRAVEL LANE, SHOULDER, DITCH and SIDE SLOPE.

TRAVEL LANE - Part of the roadway designed to accommodate the vehicular traffic. Width of lane varies between 9 feet and 12 feet depending on the amount of traffic to be handled. On some roads the width of the travel lane is widened in the curves to accommodate the OFFTRACKING of the vehicles as they turn. The drop of the surface of the travel lane is called the CROWN.

OFFTRACKING - The path of the vehicle's portion that overhangs outside the normal vehicle width as the vehicle turns - Offtracking is more pronounced in vehicles with long distances between axles such as school buses, trucks, etc. Usually the pavement is widened on sharp curves to accommodate the Offtracking.

CROWN - The traverse slope of the road surface which serves to allow water to drain. Crowns are expressed in inches per foot as 3/4" ft which indicates that the surface of the travel lane drops 3/4" for each foot of width. It is also expressed in a ratio of ft/ft like .0625 ft/ft which is equivalent to say 3/4"/ft. As the highway comes to a curve, the Crown is SUPERELEVATED.

SUPERELEVATION - The banking of the road as it goes through a curve that is used to counteract the centrifugal force. The transition between the NORMAL CROWN and the SUPERELEVATED section of the road is achieved in the SPIRAL section of the highway.

SHOULDER - The plane of the road that extends between the edge of the TRAVEL LANE and the side slope. This SHOULDER can be STABILIZED and UNSTABILIZED. The purpose of the shoulder are to allow a continuous strip or area for cars to recover if for any reason they leave the TRAVEL LANE, to accommodate stopped vehicles, to provide an area for emergency use and to create a zone for lateral support of the pavement elements.

STABILIZED SHOULDERS - Are shoulders that have been paved to allow a smoother recovery area. The width of paved shoulder varies between 2 feet and 10 feel depending on the road importance.

UNSTABILIZED SHOULDERS - Are shoulders or sections of shoulders devoid of pavement. Unstabilized shoulders are used in roads with very tow traffic volume. Also, it is the section of the shoulder adjacent to the STABILIZED SHOULDER where the GUIDE RAIL is installed and where the side slope intersects the shoulder.

GUIDE RAIL - A structure whose purpose is to contain and redirect vehicles leaving the roadway in areas where such occurrences will be certain to inflict extreme damage to the vehicles and cause injuries to its occupants. The most common types are: Box Beam, Corrugated Metal Beam, New Jersey Concrete Barrier, Wooden and Cable. Cable can use wooden, steel or concrete posts.

DITCH - Swale at the side of the road when the road goes through a cut that collects the water coming down the cut before it enters the roadway. Also, allows an area for the BASE and SUBBASE to drain. This allows the PAVEMENT to remain strong.

BASE & SUBBASE - Consecutive layers of grave! type material placed under the pavement which in conjunction with it carries the weight of the vehicles. Waterlogging is the worst enemy of these layers since it weakens their structural integrity.

SIDE SLOPE - The plane that starts at the edge of the SHOULDER when the road is elevated above the ground or at the edge of the shoulder when the road is below the natural ground and intercepts the natural ground. The steepness of the side slope is represented as a proportion like 1:4 which means that the slope rises or drops 1 foot vertically for each 4 feet or horizontal distance.

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