TRANSITION CURVE. 153 



angle ABN -- JAS. (since ABN + BAN = BNR ^ Sc) and 

 revert telescope. The transit is now in position to run in the 

 circular curve. 



With the proper superelevation for the central curve and 

 with this superelevation running off uniforml}^ on each tran- 

 sition, the complete curve laid out as described will be the 

 desired transition curve. At all points the curvature and 

 superelevation are in constant ratio and gravitational pull 

 inwards and centrifugal force outwards are balanced. Hence, 

 theoretically, and to a large extent practically, the rails will 

 suffer no side pressure from a train moving at the velocity 

 for which the maximum superelevation has been figured. 



Correction : In the figure on page 142 the upper C should be C''. 



