Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Civil, Construction, and Environmental Engineering


One thousand licensed drivers were asked a question regarding assignment of right-of-way at an uncontrolled T intersection when a vehicle on the stem of the T and a vehicle to the left of the first both arrive at about the same time. Of 487 responses to the question 68.38 percent were incorrect. After screening out those drivers who incorrectly answered a control question, there were still 50.70 percent incorrect responses. Age was the only one of the socio-economic and driving experience variables examined that were determined to be related to correctness of response. Older drivers tended to have a greater proportion of correct responses than younger drivers;Traffic and accident data were collected for randomly selected uncontrolled T and four-legged intersections. The accident rates calculated for these intersections were 0.251 accidents per million entering vehicles (MEV) and 0.733 accidents per MEV, respectively. A statistical test was performed on the difference in the rates and it was found to be significant at the 0.005 level;An interesting finding from the literature search was that eight states now have special right-of-way rules for T intersections. No research was found to provide the impetus for that legislation;It was concluded that a difference exists between drivers' perception and legal right-of-way assignment at uncontrolled T intersections. However, the lower accident rate for uncontrolled T intersections as compared with uncontrolled four-legged intersections suggested that placing STOP or YIELD signs on the stems of T intersections would not be an appropriate response to that difference. To reinforce the expectation of what appears to be a majority of drivers, the law should be changed in Iowa to give the right-of-way at uncontrolled T intersections to vehicles on the non-terminating roadway, as has been done in eight other states. More research is needed on nationwide uniformity in the laws governing T intersection right-of-way and possible revision of the Uniform Vehicle Code.



Digital Repository @ Iowa State University,

Copyright Owner

Robert Elba Montgomery



Proquest ID


File Format


File Size

166 pages