  The processes responsible for the effective longitudinal transport of solar
energetic particles (SEPs) are still not completely understood. We address this
issue by simulating SEP electron propagation using a spatially 2D transport
model that includes perpendicular diffusion. By implementing, as far as
possible, the most reasonable estimates of the transport (diffusion)
coefficients, we compare our results, in a qualitative manner, to recent
observations {at energies of 55 -- 105 keV}, focusing on the longitudinal
distribution of the peak intensity, the maximum anisotropy and the onset time.
By using transport coefficients which are derived from first principles, we
limit the number of free parameters in the model to: (i) the probability of
SEPs following diffusing magnetic field lines, quantified by $a \in [0,1]$, and
(ii) the broadness of the Gaussian injection function. It is found that the
model solutions are extremely sensitive to the magnitude of the {perpendicular}
diffusion coefficient and relatively insensitive to the form of the injection
function as long as a reasonable value of $a=0.2$ is used. We illustrate the
effects of perpendicular diffusion on the model solutions and discuss the
viability of this process as a dominant mechanism by which SEPs are transported
in longitude. Lastly, we try to quantity the effectiveness of perpendicular
diffusion as an interplay between the magnitude of the relevant diffusion
coefficient and the SEP intensity gradient driving the diffusion process. It
follows that perpendicular diffusion is extremely effective early in a SEP
event when large intensity gradients are present, while the effectiveness
quickly decreases with time thereafter.
