Cars have a steering wheel that changes their direction, but what about trains? Trains have no steering wheels; instead, they rely on turnouts and crossovers for directional changes. Railway crossings serve the same function as highway junctions, making trains cross at a point in different directions.
Generally, the type of turnouts and crossings can be divided into
1. Track divergence devices
Turnouts or switches enable trains to change route between two non-parallel tracks.
- types: single, symmetrical turnout, three-way turnout.
Turnouts, also known as switches or points, are critical components of railway tracks that enable trains to change direction or switch between tracks.
They consist of movable points, switch rails, switch devices, and tie rods, allowing trains to traverse onto different tracks. Turnouts ensure smooth transitions between tracks, providing flexibility and efficient route management in complex railway networks.
Types of turnouts
There are different types of turnouts considering their function, geometrical profile, size, inclination, and design speed
The typical types of turnouts are Standard turnout, symmetrical turnout, diamond crossing, single slip, double slip, crossover, double crossover, and lapped turnouts.
Railway turnout, Courtesy of photos on Wikimedia.com
Turnouts can also be classified according to the direction the diverging tracks go into left and right types, and also to outer and inner curve turnouts, depending on which direction the centers of the main and direction curves lie. Check more classifications in the Trackopedia article.
1.1-Standard Turnout:
A standard turnout is a commonly used railway component that allows trains to switch between two tracks. It consists of two switch rails that diverge from the main track, creating a branching path for the train to follow. The standard turnout provides a smooth transition for the train from one track to another.
1.2- Symmetrical Turnout:
A symmetrical turnout is a special type of turnout where the two diverging routes from the main track are symmetrically positioned. This means that the angle between the switch rails is the same on both sides. Symmetrical turnouts are often used in situations where balanced traffic flow is desired on both tracks.
1.3. Three-way turnout
A three-way turnout, also referred to as a three-way switch or a three-way point, is a specialized railway component that connects three tracks in a railway network. It is designed to allow trains to switch between these three tracks, providing enhanced routing options and operational flexibility.
Three-way turnout, Courtesy of photos on Wikimedia.com
The construction of a three-way turnout typically involves three switch rails diverging from a common point, forming a triangular configuration. This triangular arrangement enables trains to move from any one of the three tracks to the other two, facilitating seamless track switching and routing possibilities.
2. Parallel Track Connection Devices
Cross-overs, which are made of two or more turnouts and connecting tracks, allow movement between two tracks running side-by-side.
- Types:
- Simple crossover – one-direction connection.
- Double crossover (scissors) – two-direction connection
2.1. Crossover:
A crossover is a railway component that connects two parallel tracks, allowing trains to move from one track to another. It typically consists of two turnouts positioned side by side. Crossovers are commonly used when trains need to change tracks, such as during maintenance or to access different platforms in train stations.
Railway cross over, Courtesy of photos on Wikimedia.com
2.2. Double Crossover(scissors crossing):
A double crossover, also known as a scissors crossover, is a more complex version of a crossover. It consists of two crossovers with opposite hand orientations superimposed upon each other. In addition to the four turnouts involved, a track diamond crossing is placed between the two main tracks. Double crossovers provide the ability to switch from both tracks to the other in either direction when there is limited space to install two universal crossovers
Fig- Railway crossover, courtesy of photos on Flickr.com
3. Track Intersection Devices
Crossings are fixed rail intersections for wheel flanges to pass, where rails physically cross each other.
- Types:
- Diamond crossing, single slip turnouts, double slip turnouts
3.1. Diamond Crossing:
A diamond crossing, also known as a diamond or crossing diamond, allows two tracks to intersect each other at grade. It consists of four rails arranged in the shape of a diamond.
Railway diamond crossing, courtesy of photos on Wikimedia.com
Trains can cross the intersection by passing over the diamond-shaped crossing point. Diamond crossings are essential for enabling trains to change tracks and navigate complex rail networks.
3.2. Single Slip Turnout:
A single slip turnout is a type of crossing that provides one switching possibility. It allows trains approaching on one track to either continue over the crossing or switch tracks to the other line.
However, trains from the other track can only continue over the crossing and cannot switch tracks. Single slip turnouts are often used to provide access to sidings and improve safety by avoiding switch blades facing the usual direction of traffic.
3.3. Double Slip Turnout:
A double slip turnout, also known as a double slip, is a crossing that allows trains to change from one straight track to another while also offering the possibility of going straight across. It consists of a narrow-angled diagonal flat crossing with four pairs of points, enabling trains approaching from any direction to leave via any of the two tracks on the opposite side of the crossing. Double slip turnouts are typically used in situations where trains need to switch tracks in multiple directions.
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4. Combinations of simple turnouts, slip turnouts, and crossings.
According to the requirements of traffic directions and capacity, the different types of turnouts can be combined to form complex turnouts. The downside is that they can result in more maintenance needs and be more expensive.
A lapped turnout is used to achieve a more compact track layout in constrained locations. In a lapped turnout, the switch rails for a second turnout are placed between the switch and the frog of the initial turnout. This introduces a third frog where a closure rail of the first turnout crosses a closure rail of the second turnout. Lapped turnouts allow for efficient use of space while still providing the necessary branching paths for trains to switch tracks.
Designation of turnouts in drawings
Turnouts, crossovers, and crossings are manufactured as units in factories. They are brought to the site ready-made for installation with all their parts, including the sleepers and fastenings. They are identified by prescribed designations as per the country of reference.
The established designation of a turnout identifies all relevant track technical components of a turnout and describes its operational characteristics. The turnouts are identified by assigned standard nomenclatur,e as shown in the example of the German standard:
EW-60-760-1:18-r-Fz-B
EW … Type of turnout
60 … Shape of rail
760 … Radius of branch
1:18.5 … Inclination of the turnout
r … Direction of branch line
Fz … Type of tongue
B … Type of sleeper