Table 4.

The analogy of different track stiffness evaluation strategies. ¹⁰

S.No.	Concept	Accuracy	Speed	Research advancements
1	Standstill evaluation of static stiffness	Vertical evaluation precision is high, but the stiffness variations along the line cannot be determined.	Very slow	Typically used on heavy-haul railway tracks.
2	Continuous evaluation, static stiffness under dynamic load	Improved evaluation accuracy due to enhancing displacement evaluation	Adjustable below 60 kmph usually	Mature
3	Continuous evaluation, static stiffness under dynamic load, and high-speed deflectograph	Unsure	130 kmph, even higher	The road modulus evaluation has been successful, and the track modulus evaluation is currently underway.
4	Continuous evaluation, dynamic stiffness, excitation of the eccentric wheel, and hysteresis curve evaluation	High precision due to an approximation of hysteresis curve, stiffness, and damping factor recognition.	Slow approximate 6 kmph	Data analysis and vehicle optimization
5	Continuous evaluation, dynamic stiffness, and eccentric wheel excitation	High precision and the ability to recognize a wide range of railway track stiffness issues	High-speed of 50 kmph	Construction of a database and multi-line assessment.