## 2 Background
### First Responder's Collisions  
In first responder's collision literature, focus has been directed on emergency workers/first responders who are on foot performing their duty. Some duties include roadside pullovers, check stops, traffic control, etc. For factors in the environmental category, the discussion is centered around reduced visibility which includes nighttime driving and poor weather conditions. When there is reduced visibility, risk increases for first responders. Visibility influences reaction and response time or the time in which a driver can stop. Stopping times can vary after a driver first sees a pedestrian first responder working on the side of the roads. Night-time driving data are significant to understand because oncoming traffic/drivers must react quickly when their field of vision is reduced or compromised by oncoming vehicle headlights. Collisions during night-time driving are considerably higher than collisions during the daytime and factors such as a lighter pavement are expected to decrease headlight illumination distance and worsen visibility [25]. In a study conducted by the National Highway Traffic Safety Administration, it was found that high beam headlights are better than low beam headlights to detect pedestrians; however, there is little time to respond to moving pedestrians [26]. The limitations experienced at night are made worse when large vehicles are driven as bigger and higher vehicle hoods reduce the visibility of the driver [21]. Poor weather conditions compound these factors and reduce visibility. Drivers may not be in control of vehicles when road conditions are poor and weather such as icy roads, snow-covered roads, and heavy rain can prevent individuals from reacting quicker [5]. For the road characteristic category, reducing collisions can be achieved through safety instruments and protocols. An important protocol is the use of Traffic Control Zones (TCZ). A TCZ protects responders and maintains the flow of traffic [5]. In most cases of pedestrian workers being struck by vehicles, the TCZ was not adequately established or appropriately positioned [5]. To ensure that a TCZ is set up, there is a need for channeling devices such as signs, barricades, cones, and control vehicles, all of which are intended to assist in warning oncoming drivers of a potential threat or situation that is occurring. Without such devices, the roadside workers may be left vulnerable. In any case, road workers need to be expedient when responding to an incident. An example of this would be a police officer pulling over a driver. Police officers in this situation typically do not have the time to set up a full TCZ, and rely on their police vehicle emergency lights and siren. The sirens act as a device to signal to oncoming traffic that there is a ongoing situation and that they should be aware. Moreover, officers' protocol is to use their vehicles as a barrier that gives them room to work. For the driver characteristic category, reckless driving and driving under the influence are contributing factors that increase risks to pedestrian first responders. Research has consistently identified that driving under the influence of drugs and alcohol reduces the ability of drivers to make quick decisions, decreases the ability to track moving targets, and worsens the driver's ability to perform two tasks at the same time (distracted attention) [27]. Driving under the influence is a significant factor when vehicles strike a pedestrian or car. In addition to basic skills, knowledge of road conditions, traffic volume, time of day are all considerations. Higher usage of cell phones and other distracting devices compromise drivers' focus, which leads to more accidents and collisions [5]. Besides the common factors influencing the collisions, three other parameters can be highlighted in vehicles striking pedestrian road workers: (1) situational awareness for pedestrian first responders; (2) unmarked vehicles and unmarked first responders; and (3) lack of discretion by first responders.