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Tony's Intertwingled Memex • Reference Manual

High-Speed Railway Transition (Civil Engineering)

Formulas & Definitions

A transportation civil engineer is designing a track layout for a new high-speed passenger railway. The horizontal position profile of the track alignment transitions from a straight access track into a curved bypass, modeled by the piecewise function:

T(x)={2xfor x≤3x2−4x+9for x>3T(x) = \begin{cases} 2x & \text{for } x \le 3 \\ x^2 - 4x + 9 & \text{for } x > 3 \end{cases}T(x)={2xx2−4x+9​for x≤3for x>3​
where xxx and T(x)T(x)T(x) are measured in hundreds of meters.

  1. Analytically determine if the track layout is continuous at the junction point x=3x = 3x=3.
  2. Determine if the track layout is differentiable at x=3x = 3x=3 by comparing the left-hand and right-hand derivative limits.
  3. Based on differentiability and lateral dynamics, explain why this transition geometry is either safe or hazardous for a passenger train traveling at high speeds.