<p></p>Traffic safety management on interstates is crucial during adverse winter weather. According to the Federal Highway Administration (FHWA), there are over 5,891,000 vehicle crashes each year in the United States. Approximately 21% of these crashes are weather-related. INDOT spends $60 million on winter operations each year to minimize the weather impacts on driver capability, vehicle performance, road infrastructure, and crash risk. Several studies have sought to investigate the relationship of crash counts with weather, speed, traffic and roadway data during snow events, in order to help agencies, identify needs and to distribute the resources effectively and efficiently during winter weather events. The limitation of these studies is that weather variables are often correlated to each other, for example, visibility may be correlated to snow precipitation and air temperature may be correlated to net solar surface radiation. The randomness of crash occurrence also increases difficulty in such studies. In this study, a random parameter negative binomial model was used for Interstate I-465 in Indianapolis in winter 2018 and 2019.The results show that during snow events in Indiana, air temperature, wind speed, snow precipitation, net solar surface radiation, and visibility significantly impact the number of crashes on I-465. Driving over the speed limit (55 mph), especially on wet pavements are more likely to lose control of vehicles and cause crashes. Travel speed between 45 mph to 55 mph and travel speed between 15 mph to 25 mph are both strong factors. Somewhat surprising was that speeds between 25mph and 45mph were not found to be significant. The number of interchanges is also positively related to crash counts due to the high number of conflict points at ramp merging sections. Also, travelling over speed limit is a random parameter with unobserved heterogeneity which is intuitive since speeding could be more dangerous in certain areas with complex road geometry and narrower lanes. Traffic counts have a negative correlation with crash counts, likely due to faster speeds when fewer vehicles are travelling on the loop. Crash counts increased about70% during severe storm days on I-465, and visibility and air temperature are highly correlated to crash counts. These key findings can help the agency to deploy warnings when visibility is low, or temperature falls sharply.help the agency to deploy warnings when visibility is low,or temperature falls sharply.

Crash data suggests that intersections are areas producing conflicts among the various road users because of entering and crossing movements. Traffic signal control systems may not always be sufficient in preventing collisions at intersections between emergency and other vehicles. The Firefighter Fatality Retrospective Study of 2002 illustrates that the second leading cause of fatal injury for firefighters is vehicle collisions. Furthermore, the involvement of an emergency vehicle in a crash can negatively affect the overall efficiency of emergency response services. Thus, there is a need to facilitate the implementation of higher-payoff strategies to improve the safety of emergency vehicle passage through signalized intersections. This research aims to provide a basis for the transportation professionals to identify problem areas and take measures that will potentially enhance intersection safety for emergency vehicles. It includes the presentation and comparison of the EV crash situation in Northern Virginia. The results indicate that 49% of all EV accidents along U.S. Highways in Northern Virginia occurred at signalized intersections. This percentage is 75% along U.S. Highways in Fairfax County, the largest county in Northern Virginia, and it is 79% along U.S. 1 in Fairfax County. The analysis, also, illustrates that the major collision type at signalized intersections was of the angle type, which suggests that an appropriate warning sign may be absent. These findings enhance our understanding of emergency vehicle crash characteristics and thus, may facilitate the identification of possible warrants to be used in determining the appropriateness of installing signal preemption equipment at signalized intersections. / Master of Science