## 1 Introduction  
At the scene of a traffic emergency, the first responders including police officers, firefighters, rescuers, paramedics, and emergency medical technicians are the trained personnel who are among the first to arrive and provide assistance. Depending on the emergency circumstances, there are numerous risks that first responders may face during their response and operations. High speeds, reckless drivers, busy roads, and constant multi-faceted distractions create situations where the first responders may be at risk of being struck by vehicles while working on the side of the roads. Being struck by a vehicle represents the second-largest hazard to police officers' lives, which is a considerable risk [1; 2; 3; 4]. Furthermore, there are several responsibilities that each officer performs during a shift, which increases their exposure to collisions. For example, these duties include investigating vehicle crashes, assisting motorists, deploying/providing equipment, overseeing work zones, patrolling, performing traffic control, performing a traffic stop, and training [2].  
Past and recent data can provide some insights into these risks. Between 1998 and 2008, 141 police officer deaths resulted from officers being struck by a vehicle [3]. From 2013 to 2017, in the USA, 238 officer deaths were classified under accidental circumstances, 40 of those were pedestrian officers who were struck by a vehicle [2]. Fourteen of the 40 officers were recorded as wearing high visibility clothing, 21 were not wearing high visibility clothing [2]. The lighting conditions were dark for 8 out of the 21 victim officers who were not wearing high visibility clothing [2].  
The US fire administration recorded 1470 total deaths for firefighters between 1996-2010 [5], out of which 70 deaths were due to the firefighters being struck by a vehicle. In 2017, 18 firefighters died in vehicle-related incidents and 10 of them were struck by vehicles [6]. In 2018, 3 of 16 firefighters died of being struck by vehicles [6].  
Although the likelihood of being struck by a vehicle is low, the consequences are potentially fatal, given the speed and weight of approaching vehicles. Reducing these risks through technology development, procedural changes, training, and education require a better understanding of the underlying causes of such incidents. While police officers' data have been researched and reported much more in comparison to firefighters and emergency medical services data, lack of data and gaps in the literature suggest that research on emergency responders' collisions when on duty is still underexplored. Reducing roadside collision risks requires new technologies, practices, and training. By reviewing the existing literature and employing machine learning methods to five years of data on collisions, this paper aims to identify the factors that influence collisions between vehicles and first responders, particularly those who are working on roads.  
The paper is organized as follows. Section two provides a literature review on the parameters that have been identified as relevant to road collisions involving first responders. Section three presents the methodology and data. Statistical analysis on the National Collision Database (NCDB) of Canada, as well as the implementation of machine learning (ML) algorithms on the data, are described and discussed in section four. Section five concludes the paper, acknowledging limitations and proposing future directions in light of the findings.