  In this work, BV RI light curves of 55 Type II supernovae (SNe II) from the
Lick Observatory Supernova Search program obtained with the Katzman Automatic
Imaging Telescope and the 1 m Nickel telescope from 2006 to 2018 are presented.
Additionally, more than 150 spectra gathered with the 3 m Shane telescope are
published. We conduct an analyse of the peak absolute magnitudes, decline
rates, and time durations of different phases of the light and colour curves.
Typically, our light curves are sampled with a median cadence of 5.5 days for a
total of 5093 photometric points. In average V-band plateau declines with a
rate of 1.29 mag (100 days)-1, which is consistent with previously published
samples. For each band, the plateau slope correlates with the plateau length
and the absolute peak magnitude: SNe II with steeper decline have shorter
plateau duration and are brighter. A time-evolution analysis of spectral lines
in term of velocities and pseudoequivalent widths is also presented in this
paper. Our spectroscopic sample ranges between 1 and 200 days post-explosion
and has a median ejecta expansion velocity at 50 days post-explosion of 6500
km/s (Halpha line) and a standard dispersion of 2000 km/s. Nebular spectra are
in good agreement with theoretical models using a progenitor star having a mass
<16 Msol. All the data are available to the community and will help to
understand SN II diversity better, and therefore to improve their utility as
cosmological distance indicators.
