  We carry out a systematic study of interferometry radii in ultrarelativistic
heavy-ion collisions within a two-dimensional transport model. We compute the
transverse radii R_o and R_s as a function of p_t for various values of the
Knudsen number, which measures the degree of thermalization in the system. They
converge to the hydrodynamical limit much more slowly (by a factor 3) than
elliptic flow. This solves most of the HBT puzzle for central collisions:
R_o/R_s is in the range 1.1-1.2 for realistic values of the Knudsen number,
much closer to experimental data ($\simeq 1$) than the value 1.5 from
hydrodynamical calculations. The p_t dependence of R_o and R_s, which is
usually said to reflect collective flow, also has a very limited sensitivity to
the degree of thermalization. We then study the azimuthal oscillations of R_o,
R_s, and R_{os} for non central collisions. Their amplitudes depend little on
the Knudsen number, and reflect the eccentricity of the overlap area between
the two nuclei.
