Checking the versine survey precision

A field measurement of any kind is never exact and intrinsically contains errors (NJDoT Survey Manual – 2014). For track topographical measurements some of these errors are known and eliminated by applying appropriate corrections and compensations. Even after all known errors are eliminated however, a site measurement will still be in error by some unknown value. To minimise the…

Types of versines used for track realignment methods

There are three types of versines used for the track realignment and rectification methods (Radu, 2003): Measured (existing) versine – the versine measured with a real chord on the outer rail of the real existing track. This is the result of the versine (Hallade) survey and based on it are computed the track offsets (slues…

Track Realignment and Rectification

The running of the trains over the railway track is inducing vertical and lateral forces that, in time, are affecting the track alignment, changing incrementally the installed track and causing track irregularities.  On curved track this deterioration process is more significant due to the additional effect of the lateral (centrifugal) acceleration. When the irregularities become…

Mauzin (Hallade) track measurement car

The measurement and analysis of track geometry is carried out regularly by all the railway infrastructure administrators in order to obtain data from which the track quality is established and the maintenance can be scheduled (Cope – 1993). Historically, the use of track inspection cars can be traced back to the early 1920’s in France…

Chainage creep

When designing multiple line alignments – in railway stations or plain line sections – there will be a creep of the alignment stationing due to the length difference between the alignments. This stationing (or chainage) creep becomes relevant when adjacent alignments have to be kept at the same level or with a well-defined elevation difference.…

Maglev Guideway Design

Maglev is a transport system that uses the magnetic levitation to move vehicles without contact to the guideway. The system uses magnetic forces for levitation, propulsion and guidance of the vehicle, thereby making practically negligible the friction forces and allowing very high speeds. The technological evolution is making this transportation system competitive and gaining consideration as a…

The orphan rule of cant design over a reverse transition

Motto: Tolle lege. Most of the railway track design standards around the world are presenting the particular issue of the reverse transition. All these standards are insisting on keeping a constant rate of change of curvature – a constant A. By doing this in fact the design will include a single continuous transition between the two opposite circular…

The Clothoid

INTRODUCTION In transportation infrastructure design the route is defined based on its axis (centreline) – the alignment model. This simplified abstract model is designed in such a way to clearly define the principle course of the infrastructure project. For most of the transportation means the infrastructure alignment design is split into two main two-dimensional complex…

Circle or “egg”?

After the post about the limits of vertical acceleration, and even before, I was asked what was the original curve used to connect vertical gradients. What was first, the circle or the “egg”- the parabolic curve? The expected answer was “the circular curve” because, presumably, a circle can be drawn easier than a parabola… “How…