When it comes to Railway track engineering literature, there are a few books we can consider “classic”. Even old, some very old, these books still have significant railway engineering value and can be always a good reference both for young and inexperienced engineers as for the ones that already have robust railway track experience and knowledge.

One of these books is the French book “La voie ferrée: techniques de construction et d’entretien” (The railway track. Construction and maintenance techniques) written by Jean Alias, honorary Railway Track professor at the École nationale des ponts et chaussées.

Jean Alias. La voie ferrée: techniques de construction et d’entretien. Eyrolles. 1984

Among other important and interesting railway track subjects, the book describes in a few words and a simple drawing where should we place the cant transition when the horizontal alignment has a sudden change in curvature:

Jean Alias. La voie ferrée – cant transition over a sudden change in curvature.

When we design a cant and alignment transition it is obvious to place them together without the fear of some dangerous overlapping effects – we know the cant and curvature transitions work together very well. We have even well defined concepts that tie together the cant and curvature variation.

But what is the logical (and “railway scientific”) thing to do when we need to insert a cant transition in an area of a sudden change in curvature – a “virtual transition”?

Where should we then place the cant transition?

Is there any technical reason not to do what the venerable Monsieur le Professeur Alias is well describing in the picture above?

(to be continued)