  The collision-free velocity model is a microscopic pedestrian model, which
despite its simplicity, reproduces fairly well several self-organization
phenomena in pedestrian dynamics. The model consists of two components: a
direction sub-model that combines individual desired moving direction and
neighbor's influence to imitate the process of navigating in a two-dimensional
space, and an intrinsically collision-free speed sub-model which controls the
speed of the agents with respect to the distance to their neighbors.
  In this paper we generalize the collision-free velocity model by introducing
the influence of walls and extending the distance calculations to
velocity-based ellipses. Besides, we introduce enhancements to the direction
sub-module that smooth the direction changes of pedestrians in the simulation;
a shortcoming that was not visible in the original model due to the symmetry of
the circular shapes. Moreover, the introduced improvements mitigate backward
movements, leading to a more realistic distribution of pedestrians especially
in bottleneck scenarios.
  We study by simulation the effects of the pedestrian's shape by comparing the
fundamental diagram in narrow and wide corridors. Furthermore, we validate our
generalized approach by investigating the flow through bottlenecks with varying
exit's widths.
