Function update_placing_train 

fn update_placing_train(
    cmd: Commands<'_, '_>,
    q_train: Single<'_, '_, (&VirtualTrain, &TrackPos), Without<VirtualBogie>>,
    q_carriages: Query<'_, '_, &VirtualCarriage>,
    q_bogies: Query<'_, '_, (Entity, &mut TrackPos), With<VirtualBogie>>,
    q_segments: Query<'_, '_, (Entity, &TrackSegment, &Transform)>,
    q_nodes: Query<'_, '_, (Entity, &TrackNode)>,
    next_state: ResMut<'_, NextState<PlacedTrainState>>,
)

System which updates virtual train’s bogies positions according to head train position