The Kowloon-Canton Railway has opened two new suburban rail routes in Hong Kong. Initially, these lines used the high-conicity P8a wheel profile and the UIC60 rail profile. Problems were experienced with the wheel/rail interface, including disappointing wheelset life, high vibration due to hunting instability and rapid growth of rolling contact fatigue (RCF) damage on the high rail in curves. Careful analysis using established wheel/rail interface modelling techniques and innovative validated RCF prediction algorithms has led to the development of an optimised wheel/rail interface. The combination of the low-conicity P8y wheel profile and the CEN60-E2 rail profile, with effective lubrication, has given substantial improvements in re-profiling intervals, improved running stability and has led to a massive reduction in RCF damage.