For the study of the charge transport mechanism of equilibrium charge carriers in pi-conjugated polymers we use a novel, still technically simple method, namely charge extraction in a linearly increasing voltage (CELIV). We briefly outline the method and use it to study the temperature and electric field dependence of the mobility in regioregular poly(3-octylthiophene). We find that mobility can be explained using the well-known Poole-Frenkel type of law mualphamu(0)(T)exp[B(T)rootE], with an activated zero-field mobility. We also find that the nature of the mobility is determined by the release time from traps in regioregular poly(3-hexylthiophene).