A curve is nothing more than an arc that joins two straight lines separated by an angle known as the deflection angle. When the alignment of a road or rail line changes due to unavoidable objects or situations, this is known as a directional change. A curve is provided for the ease of vehicle movement at this location, which could be a hill, a lake, or a temple, for example. Curves in Highway Alignment Curves of Different Types in Highway Alignment There are two types of curves in general, and they are: Curves that run horizontally Curves that run vertically Curves that run horizontally The horizontal curve is the curve that is provided in the horizontal plane of the earth. It joins two straight lines that are on the same level but at different heights.

## What is a Curve in Roads

A compound curve is made up of two or more simple circular curves with various radii combined into one. Both or all of the curves are on the same side of the common tangent in this example. Curve Compound Curve Compound Curve in the opposite direction When two basic circular curves bend in opposite directions meet at a point, a reverse curve is generated. This is referred to as a point of reverse curvature. Both curves have their centres on opposite sides of the shared tangent. Both curves’ radii could be the same or different. Curve in the opposite direction Curve of Transition A transition curve is a curve with a changeable radius. It is commonly found on the sides of circular curves, between tangent and circular curves, and between two circular curves.

between two complex curves or reverse curves, and so on. It has a radius that ranges from infinity to the radius of the circular curve. The transition curve aids in the progressive introduction of centrifugal force through gradual super elevation, providing comfort for passengers in the vehicle without jerking. Curve of Transition Curve in a Spiral Because of its seamless introduction of centrifugal acceleration, the IRC recommends the spiral as an ideal transition curve. Clothoid is another name for it.Curve in a Spiral Lemniscate When the deflection angle is quite large, a transition curve called a lemniscate is used. The radius of a lemniscate curve is greater when the chord length is less. Lemniscate Curves that run vertically Vertical curves are presented.

## Vertical Curves

Vertical curves are the curves that are offered in the vertical plane of the earth. When the ground is non-uniform or contains varying levels at different spots, this type of curve is offered. For vehicle travel, a parabolic curve is preferred as a vertical curve in the vertical alignment of the roadway. Vertical curves are classified into two sorts based on their convexity. Curve of the valley Curve at the top Curve of the Valley Because a valley curve unites a falling gradient with a rising gradient, the curve’s convexity is often downwards in this scenario. It’s also known as the sag curve.Curves that run vertically Curve of the Valley Curve of the Summit The convexity of the curve is upwards because the summit curve connects rising and descending gradients. It’s also known as a crest.

A highway curve is an arc that joins two straight lines separated by a deflection angle of some kind. When the alignment of a roadway or railway changes due to unavoidable objects or situations, this is known as a directional change. In highway construction, there are two sorts of curves: horizontal curves and vertical curves. When a route changes direction from right to left (or vice versa) or changes alignment from up to down, curves are presented (vice versa). Curves are an important part of pavement design. They are given a maximum speed limit, which must be rigorously adhered to. Following the speed limit is critical since exceeding it increases the risk of the vehicle becoming involved in an accident.

## Importance of curves in highway

Also, to make the infrastructure road user-friendly and reduce the chances of hazardous situations, proper safety measures must be implemented at all horizontal and vertical curves. Curves in highways are crucial. A progressive curvature is supplied to continue forward towards the objective if there is a sudden impediment in the middle of the roadway, such as mountains, rocks, etc., which are impossible to move. Highways are often straight highways with longer lengths, therefore accidents due to overspending or drowsy driving are more likely to occur. If the curvature is provided, the driver becomes more aware of his surroundings and is able to control his speed and tiredness while driving. If a curve is given, drowsiness is the leading cause of highway accidents.

Horizontal and vertical curves are the two types of curves. Each one has its own set of subcategories, which are detailed below. Curves that run horizontally A horizontal curve is a curve that exists in the horizontal plane of the ground or earth. It joins two straight lines that are on the same level but have opposite or complementary directions. Horizontal curves come in a variety of shapes and sizes, each of which is described here.Curve is circular and simple. It’s a curve made up of a single arc with a fixed radius that connects the two tangents. It is the most common sort of horizontal curve. The simple arc is a curve imposed between two straight lines by placing a simple arc in the road or railway track.

## Compound curve

It’s a curve made consisting of two or more circular arcs of gradually shorter or longer radii, linked tangentially without reversal of curvature, and used as an easement curve on some railroad tracks and highways to make the transition from tangent to complete curve or vice versa less jarring. Compound curves fit the topography considerably better than simple curves since their tangent lengths vary. These curves adapt well to mountainous terrain or regions where huge, winding rivers cut through. Compound curves, on the other hand, are more dangerous than simple curves and should never be utilised where a basic curve will suffice. Curves that run horizontally Invert the curve Two or more basic curves turning in opposing directions make up a reverse curve. Their junction points are located on.

A track transition curve, also known as a spiral easement, is a mathematically calculated curve on a stretch of highway that transforms a straight portion into a curve. Its purpose is to prevent abrupt shifts in lateral movement. The start of the transition of the horizontal curve in plane (viewed from above) is at infinite radius, and the end of the transition has the same radius as the curve itself, forming an extremely large spiral. Simultaneously, the outside of the curve is gradually elevated in the vertical plane until the correct degree of bank is obtained. Curve in a spiral Spiral curves are commonly utilised to offer a gradual transition from a straight to a curved segment of road. They provide assistance.

## Vertical curves

The purpose of using a spiral is to have the road or track take the same shape as the vehicle. You don’t go from going straight to fully turning in an automobile. There is a transition area where the steering wheel is slowly turned. The lanes on highways are broad enough that you can drive a spiral by just shifting from one side of the lane to the other. Curves that run vertically These curves are used to adjust the road’s slope and can be symmetrical or asymmetrical. They are not circular like horizontal curves, but rather parabolic. The main design criterion of the vertical curve is to determine the proper grade and safe passing sight distance. The length of the crest vertical curve should also be determined.

**How many types of highway curves are there?**

There are two types of curves – Horizontal and Vertical curves.

**Why are there curves in highways?**

Vertical curves are used to provide a gradual change from one road slope to another.

**What are the different types of vertical curves?**

Two types of vertical curves exist: (1) Sag Curves and (2) Crest Curves.

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