Document Type


Date of Award

Fall 1-31-2011

Degree Name

Doctor of Philosophy in Transportation - (Ph.D.)


Civil and Environmental Engineering

First Advisor

Janice Rhoda Daniel

Second Advisor

Lazar Spasovic

Third Advisor

I-Jy Steven Chien

Fourth Advisor

Athanassios K. Bladikas

Fifth Advisor

RongFang Liu


Factors influencing seat belt usage have been extensively researched in the safety analysis literature. Most of this research has focused on factors that influence seat belt usage for a driver and front seat passenger in a vehicle. Few research studies have investigated factors that impact seat belt usage for back seat occupants. This research investigates the factors associated with seat belt usage for front-seat as well as backseat occupants of vehicles in the state of New Jersey. Using logistic regression, seat belt usage models were developed to examine the contribution of several variables on seat belt usage for five vehicle occupants.

The age of the occupant was found to be a significant factor for influencing the seat belt usage of both the driver and the right-back passenger. Gender was determined to be a significant variable for all of the models, with the exception of the right-back seat occupant model. The models show that in general male occupants in the front-seat tend to be less likely to wear a seat belt compared to female occupants. The results are just the opposite for back seat occupants. The results showed that a driver traveling alone is less likely to be belted than if he or she was driving with another passenger. The results also indicated that more occupants in the vehicle increase the likelihood that the back-seat occupants are buckled. Occupants on urban principal arterials were found to be more likely to be belted than on other roadways. The driver's seat belt usage was found to be significant for all the non-driver seat belt usage models.

Essentially, research and enforcement campaigns on seat belt usage have been focus on front seat occupants. Seat belt usage for back seat occupant is also very important. Unbelted back seat occupants put themselves and other occupants at serious risk when riding unbuckled. A comprehensive literature review on back seat passenger seat belt usage was conducted in this research. Injury severity models were developed in this research to obtain injury severity level of drivers and right-front seat occupants in motor vehicle crashes, using several independent variables. Using SPSS version 10.00 Statistical software, ordinal logistic regression models were developed. The results showed among other variables that seat belt usage by back seat occupants has an impact on the injury severity of front seat occupants. In particular, the impact is greater as the number of back seat occupants in the vehicle during a crash increases.



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