We choose k0 = 30 au as a representative high-energy case for the ECR model. As the kinetic energy is large enough, the WP on the upper PES can overcome the barrier such that trajectory branching does not occur. In Figure , we show the time evolution of population distributions. Despite the absence of strong branching events, correctly characterizing the slow WP splitting is still important. When the WP enters the branching region at t = 1000 au, the wavefunction-based methods begin to deviate from the exact results due to the lack of decoherence (see Figures and). The population peaks by both FSSH-wf and BCSH-wf are located at the same positions on the upper and lower PESs, while the population distribution by BCSH-as properly depicts the slight separation of population peaks on the two adiabatic PESs. After the WP on the upper PES overcomes the barrier (e.g., t = 1400 and 1800 au), the fully quantum dynamics still exhibits only one single peak on each PES, but FSSH-wf and BCSH-wf show two peaks on both upper and lower PESs due to overcoherent propagation of the electronic wavefunction. In contrast, BCSH-as exhibits accurate distributions, as active states of the trajectory ensemble could capture the slow splitting of WPs.