  Intersection safety often relies on the correct modelling of signal phasing
and timing parameters. A slight increase in yellow time or red time can have
significant impact on the rear end crashes or conflicts. This paper aims to
identify the relationship between surrogate safety measures and signal phasing.
Unmanned Aerial Vehicle (UAV) video data has been used to study an
intersection. Post Encroachment Time (PET) between vehicles was calculated from
the video data as well as speed, heading and relevant signal timing parameters
such as all red time, red clearance time, yellow time, etc. Random Parameter
Ordered Logit Model was used to model the relationship between PET and these
signal timing parameters. Overall, the results showed that yellow time and red
clearance time is positively related to PETs. The model was also able to
idendity certain signal phases that could be a potential safety hazard and
would need to be retimed by considering the PETs. The odds ratios from the
models also indicates that increasing the yellow and red clearance times by one
second can improve the PET levels by 16% and 3% respectively.
