<p>The Chinese No.18 high-speed turnout with a radius of 1100&#xa0;m is widely used in railway station entry and exit lines, and it is an important component to allow high-speed trains to switch tracks before or after the stations. A curved blade with variable cross-sections usually faces enormous wear issues due to frequent lateral wheel-rail interactions in the switch panel, and the transition area between stock and switch rails is defined empirically from the switch rail section with a head width of 20&#xa0;mm to 50&#xa0;mm to avoid high loadings at the thin cross-sections. This paper aims to study the wheel-rail interaction in the switch panel and discuss the transition area changes considering the deviation of track conditions, including the track gauge, wheel-rail friction coefficient, height difference between the stock and switch rails, and width of the switch rail. Firstly, a high-speed vehicle model with a speed of 80&#xa0;km/h in the diverging route and a co-running track model with various rail profiles are established. Secondly, the dynamic response of the vehicle negotiating the diverging route is studied when the track is in perfect condition. The results show that the transition area from the stock rail to the switch rail in the facing move is within the range of 4.6 and 8.4&#xa0;m from the switch toe when using intact wheel and rail profiles, and the corresponding width of the switch rail head is between 23.67 and 47.98&#xa0;mm, which perfectly meets the requirement. Due to frequent service and severe wear, the track condition varies on-site. A parametric study indicates that the deviation in height difference between the stock and curved switch rails significantly influences the transition area. The height of the switch rail at the end of the transition area should be equal to or slightly higher than the stock rail to avoid the dropping impact. This study could provide guidance for rail grinding maintenance in the switch panel.</p>