'roads to power' (or success) are the 4 following qualities, "for as guides, they indicate the road to power connected therewith; and because they form, by way of preparation, the roads to the power constituting the fruition of the path" (Vis.M. XII), namely:
"concentration of intention (chanda-samādhi) accompanied by effort of will (padhāna-sankhāra-samannāgata), concentration of energy (viriya-samādhi) ... concentration of consciousness (citta-samādhi) ... and concentration of investigation (vimamsa-samādhi) accompanied by effort of will."
As such, they are supermundane (lokuttara, i.e. connected with the path or the fruition of the path; s. ariyapuggala) But they are mundane (lokiya, q.v.) as predominant factors (adhipati; s. paccaya 3), for it is said: "Because the monk, through making intention a predominant factor, reaches concentration, it is called the concentration of intention (chanda-samādhi), etc." (Vis.M. XII).
"These 4 roads of power lead to the attaining and acquiring of magical power, to the power of magical transformation, to the generation of magical power, and to mastery and skill therein" (Pts.M. II. 205, PTS). For a detailed explanation, s. Vis.M. XII.
"Once the monk has thus developed and often practised the 4 roads to power, he enjoys various magical powers, ... hears with the divine ear heavenly and human sounds, ... perceives with his mind the mind of other beings ... remembers many a former existence ... perceives with the divine eye beings passing away and reappearing, ... attains, after the extinction of cankers, deliverance of mind and deliverance through wisdom, free from. cankers.... (S. LI, 2). For a detailed explanation of these 6 higher powers, s. abhiññā.
"Whosoever, o monks, has missed the 4 roads to power, he has missed the right path leading to the extinction of suffering; but whosoever, o monks, has reached the 4 roads to power, he has reached the right path leading to the extinction of suffering" (S. LI, 2).
See the chapter on Iddhipāda in The Requisites of Enlightenment by Ledi Sayadaw (WHEEL 169/172).