I'm conducting a research about the impact of BRT lane on number of crashes.it's before/after study with using eb method.I have data for crashes and traffic exposure for 3 years.treated sites are defined and my questions are as follows:
1. is it necessary to consider non treatment sites ?
2. what's a difference between reference sites and comparison sites ?
please note that a BRT lane was constructed at 2012
Thanks for your time and consideration