Flexural fatigue is one of the main failure modes in asphalt mixtures. After reviewing and critiquing the current literature about fatigue in pavement engineering, this research project focused on dissipated energy approach because it takes into account the evolution of the material during a test. A comparison between the traditional method and several dissipated energy methods was made by using statistical analysis. Further research investigation involved the understanding of fatigue testing machines. Different categories of tests give different fatigue life values; so which one best represents the real world? This project focuses on pure fatigue tests and diametrical fatigue tests. The main innovative contribution of this thesis is the development of a new fatigue test: ITFT in strain controlled mode. It is a simple fatigue test widespread in UK often used by civil engineering firms to characterise stiffness and fatigue properties of asphalt materials mostly for construction and maintenance sites. Currently, the ITFT characterises the behaviour of asphalt material under repeated constant load; so no ITFT data obtained in strain control mode exist. To overcome this lack, ITFT in strain control mode was developed; this allows comparing results between simple flexural tests and diametrical tests. Results show that fatigue lives obtained by means of the ITFT are smaller than fatigue lives obtained by pure fatigue tests, this is due to the accumulation of permanent deformation during the ITFT; however ITFT results are reliable and statistically not different from 4PB results. It is true that pure fatigue does not really exist in real life; failure is a more complicated phenomenon. Thus, developing ITFT in strain control mode could reduce the gap between research in laboratory (where pure fatigue tests often are used) and in the fields (where experience showed that quick and simple tests are preferred by engineering consultancies).