Road safety normally hinges on the environment, roadway and vehicular factors. The interaction between vehicles is largely ignored in road safety analysis. How can we factor vehicular interaction into the road safety equation.
In traffic there are many various kinds of interactions/encounters, with different safety consequences. For introduction, see safety pyramid/hierarchy concept in Aliaksei Laureshyn's thesis (chapter 2.3) - http://portal.research.lu.se/ws/files/5337337/1522970.pdf
Jiri, you always beat me... Please also consider conflict analysis. This applies to intersections mainly. This is a very dynamic field of research at the moment with practical applications emerging. It draws on microsimulation modelling.
You may need a CCTV footage or a helicopter view to analyse the space between different vehicles such as trucks, buses, cycles, scooters, cars etc. and their speed characteristics.