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1. Corporate Induction
2. Railtrack Zone
3. Electrification and Plant Appreciation
4. Plant Maintenance
5. Maintenance Planning
6. Track Design
• Estimating
• Surveying
• Basic Design
• Curves
• Deficiancy and Cant
• Gauging
• Track Inspection
• Clearance analysis
• Center and End Throw
• Buffer Locking
• Stepping Distances
• Design Proceedure
• Evaluation
7. Vehicle Systems Design
8. Manufacturing
9. Track Renewals
10. Electrification Testing and Commisioning
11. Electrification Design and Construction
12. Overhead Line and Track Renewals
13. Career Directed Experience
 
14. Links

Curvature

The most important thing to understand is that all curves are typically measured in versines. To measure the versine of a curve, several chords have to be measured. Following this, the points from where the chords cross, to the running edge of the curve is called the versine. The following diagram emphasises how a versine is measured.

Fig. 64 How the versine of a curve is measured.  

Once the versine is known, the radius of the curve can be calculated. If the versines around a curve are similar or constant, the curve is smooth.

With regards to horizontal and vertical design, if curves are involved, a transition rail may have to be used. This is typically used where a design incorporates a curve to curve section, or a straight to curve section.

As can be seen in Figs. 65, 66 and 67, the use of a transition rail makes the curve much smoother. Figs 65 and 66 show how vertical curves are used to run rail over hogs (hill) and sags (valley). Without the use of transition curves, the train would have a very rough ride and the rail would be subjected to many unnecessary forces.

Meanwhile, Fig. 67 shows why horizontal curves have to be used. Again, giving a much smoother ride, there is no unnecessary forces exerted on the rail.

In both cases, the aim is to provide an easy route for the train.

A transition rail is used if two curves of different versines are joined. A graph can be shown to represent the versine profile of the track. This is seen in Fig. 68. As seen, one curve of versine x is joined to a second curve of versine y by a length of rail with increasing versine. Ideally, this is a linear relationship.