A tale of intersection types

Safety performance functions (SPFs) are essential tools to help agencies predict crashes and understand influential factors. Florida Department of Transportation (FDOT) has implemented a context classification system which classifies intersections into eight context categories rather than the three classifications used in the Highway Safety Manual (HSM). Using this system, regional SPFs could be developed for 32 intersection types (unsignalized and signalized 3-leg and 4-leg for each category) rather than the 10 HSM intersection types. In this paper, eight individual intersection group SPFs were developed for the C3R-Suburban Residential and C4-Urban General categories and compared with full SPFs for these categories. These comparisons illustrate the unique and regional insights that agencies can gain by developing these individual SPFs. Poisson, negative binomial, zero-inflated, and boosted regression tree models were developed for each studied group as appropriate, with the best model selected for each group based on model interpretability and five performance measures. Additionally, a linear regression model was built to predict minor roadway traffic volumes for intersections which were missing these volumes. The full C3R and C4 SPFs contained four and six significant variables, respectively, while the individual intersection group SPFs in these categories contained six and nine variables. Factors such as major median, intersection angle, and FDOT District 7 regional variable were absent from the full SPFs. By developing individual intersection group SPFs with regional factors, agencies can better understand the factors and regional differences which affect crashes in their jurisdictions and identify effective treatments.

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Positioning Practices of Orientation and Mobility Specialists When Teaching Street Crossings: Is There a Standard Approach?

Journal of Visual Impairment & Blindness ◽

10.1177/0145482x211000947 ◽

2021 ◽

Vol 115 (2) ◽

pp. 85-94

Author(s):

Kim T. Zebehazy ◽

Rebecca L. Renshaw ◽

George J. Zimmerman

Keyword(s):

Future Research ◽

Personnel Preparation ◽

Demographic Information ◽

Preparation Programs ◽

Variable Position ◽

University Personnel ◽

Orientation And Mobility ◽

Intersection Types ◽

Standard Strategy ◽

Question Survey

Introduction: An important skill for orientation and mobility (O&M) specialists to have is to monitor clients appropriately when they are learning to cross intersections. Techniques books provide some suggestions for positioning during street crossings, but no research has been conducted about consensus or priorities for making appropriate decisions on positioning. The purpose of this study was to investigate general positioning decisions using visual monitoring techniques. Method: A total of 234 participants (practicing O&M specialists, preservice O&M students, and O&M university personnel) completed a 40-question survey. The survey included demographic questions, diagrams of intersections that participants used to select positioning locations, questions about lanes of threat, and questions about important factors to consider when positioning to monitor safety. Commonality of selections were analyzed and compared with demographic information. Results: The greatest consensus was found for all intersection types when the client is positioned on the corner waiting to cross and for identification of the first lane of threat. More variable position selections were made for monitoring during the crossings, and the second and third lane of threat selections were also more variable. Factors respondents indicated as most important to consider when positioning aligned with their positioning choices overall. Discussion: Personnel preparation programs may want to consider to what extent they teach considerations for positioning before and during crossings, and whether the predominant tendency to put oneself between the client and traffic warrants additional conversation. Future research should look at more complex intersections and the additional nuances used to make positioning choices. Implications for practitioners: Practitioners should reflect on whether they actively change their positioning decisions based on the situation and type of intersection versus tending to use a standard strategy.

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