Absolute dissociative and non-dissociative ionization cross sections of CHn+ (n = 0-4) molecules by protons in the 0.5-3.5 MeV impact energy range have been measured. The present results are in good agreement with the previously published data, where overlap occurs. A decay-route model for CH4 dissociation induced by proton impact is proposed and a method to obtain the corresponding branching ratios is introduced. The consistency and extent of the proposed model and methodology is verified through its application in the case of electron-impact dissociation.