Available at: https://digitalcommons.calpoly.edu/theses/411
Date of Award
MS in Civil and Environmental Engineering
Civil and Environmental Engineering
Anurag Pande, Ph.D.
National and statewide (California) collision numbers are currently on the
decline; however, the U.S. is declining at a much slower rate than most other
developed countries, and in some aspects is actually regressing in terms of traffic
safety. Although state highway safety is improving, local roadway safety may
actually be regressing. Approximately three-quarters of all U.S. public roadways,
and approximately 80% of all injury accidents fall under the jurisdiction of cities.
However, cities may not be allocating the proper level of resources, or operating
under the proper administrative methodologies to adequately address these
This research finds that on average, California cities are experiencing
increasing annual collision rates. In particular, small cities with populations of
less than 25,000 are experiencing the largest increases, whereas larger cities are
experiencing static or slightly decreasing collision rates. California’s statewide
collision statistics and the administration surveys conducted as part of this study
indicate that there is a correlation between a city’s administrative
analysis/mitigation methodologies and their annual collision rate trends.
Specifically, cities with lower traffic engineering staff to population ratios tend to
have increasing collision rates, as opposed to cities with high staff to population
ratios, which have decreasing collision rates. Also, this research shows that cities
that allocate more traffic safety resources to enforcement over engineering tend
to have increasing collision rates, as opposed to cities allocating more resources
to engineering that have decreasing collision rates.
This research also finds that there are predominant and correctable
factors that lead to the various collision types. Cities that employ routine system
wide traffic safety audits addressing location-specific collision trends based on
these predominant factors tend to have decreasing collision rates, as opposed to
those that do not.
In general, collision rates among U.S. cities are increasing largely due to
increasing rates on roadways within the jurisdiction of smaller cities, most
commonly with populations under 25,000. Over one-third of cities are not staffed
at the proper levels, not allocating the necessary resources to traffic engineering
activities, and are not employing an adequate evaluation/mitigation strategy. The
findings of this study provide guidance and framework to cities for developing
effective traffic safety strategies by identifying the characteristics of those cities
that have been successful in reducing collision rates as examples. In particular
the value of this research is important for non-engineering administrative staff
and political bodies in terms of establishing appropriate staffing levels and
resource allocations necessary for an effective traffic safety program.
The findings of this study provide guidance and framework to cities for
developing effective traffic safety policy preference by identifying the
characteristics of those cities that have been successful in reducing collision
rates as examples. In particular this research is important for non-engineering
administrative staff and political bodies in terms of establishing appropriate
staffing levels and resource allocations necessary for a transportation
department to be effective in reducing traffic collisions and resulting damages.