The most important factors for public transport usage is reliability (it comes on time) speed and frequency(under 5-10 min wait time depending on area). For high demand areas- trams, for lower demand - trolleys or busses.

To achieve reliability speed and frequency transport needs own lanes and semaphore priority. If there are too few lanes - make one lane dedicated to pub transport and another - single direction for cars. Voila. You can start at worst with 15-20 min wait time, but reliable, and increase nr or units where demand is higher up to using a tram

Everything else has secondary priority. Even the mentioned safety aspect - it'll matter much less if the next bus will come in 5-10 mins and you can skip the current one because of some drunk ppl.