A method of selecting a transport format (11) for transmission of data blocks between a base station and a mobile terminal in a wireless telecommunications system, wherein the mobile terminal is capable of moving at a speed relative to the base station, comprises determining (101) transport formats (11) possible for transmission of data blocks from the device (1); and determining (102) for each possible transport format a set of quality metrics (12). The method further comprises determining (103) for each possible transport format modified sets of quality metrics (13, 14, 15, 18) in dependence of speed and code rate for different speeds; estimating (104) the speed of the mobile terminal, and selecting (105) one of said possible transport formats (11) for transmission of a data block in dependence of said estimated speed and said modified sets of quality metrics (13, 14, 15, 16). This provides a method of selecting a transport format (11) with improved performance in high speed conditions.