SEGMENTATION STRATEGIES FOR ROAD SAFETY ANALYSIS

This dissertation addresses the relationship between roadway segment length and roadway attributes and their relationship to the efficacy of Safety Performance Function (SPF) models. This research focuses on three aspects of segmentation: segment length, roadway attributes, and combinations of the two. First, it is shown that choice of average roadway segment length can result in markedly different priority lists. This leads to an investigation of the effect of segment length on the development of SPFs and identifies average lengths that produce the best-fitting SPF. Secondly, roadway attributes are filtered to test the effect that homogeneity has on SPF development. Lastly, a combination of segment length and attributes are examined in the same context. In the process of conducting this research a tool was developed that provides objective goodness-of-fit measures as well as visual depictions of the model. This information can be used to avoid things like omitted variable bias by allowing the user to include other variables or filter the database. This dissertation also discusses and offers examples of ways to improve the models by employing alternate model forms. This research revealed that SPF development is sensitive to a variety of factors related to segment length and attributes. It is clear that strict base condition filters based on the most predominant roadway attributes provide the best models. The preferred functional form was shown to be dependent on the segmentation approach (fixed versus variable length). Overall, an important step in SPF development process is evaluation and comparison to determine the ideal length and attributes for the network being analyzed (about 2 miles or 3.2 km for Kentucky parkways). As such, a framework is provided to help safety professionals employ the findings from this research

Evaluation of Pavement Marking Performance

The objective of the investigation was to evaluate the useful life of pavement markings. The Manual on Uniform Traffic Control Devices (MUTCD) provides general guidelines for the application and installation of pavement markings. However, performance requirements for various types of pavement markings are not included. Retroreflectivity data were collected throughout Kentucky on various longitudinal pavement markings using mobile and manual techniques. Data were collected on two-year old and one-year old lines. The retroreflectivity levels were analyzed and the several recommendations were made. Minimum levels of retroreflectivity should be set for determining what roads to restripe annually. These values should be lower than the passing/bonus thresholds used in the Quality Control/Quality Assurance (QA/QC) program. It is recommended that yellow lines should be above 100 mcd/m2/lux and white lines should be above 150 mcd/m2/lux. Retroreflectivity measurements should be collected and used to determine which roads should be painted each year. The current Maintenance Rating Program (MRP) can be used to facilitate this process. An inventory of striped roads should be maintained to allow a determination of when specific roadway sections were last restriped. The effect of the amount of beads per gallon on retroreflectivity should be studied further; however it seems fewer beads could be used

Crash Data Analysis Tool: Research Report + User Guide

This manual describes the Crash Data Analysis Tool (CDAT), which can be used by KYTC staff and the agency’s work partners to securely access crash datasets. CDAT users can query and download data using flags stored during post-processing. Unlike KyOPS, however, CDAT’s location data are validated using geographic coordinates and several of county, route, and milepoint fields to ensure crashes are properly geocoded. CDAT grants access to data and information that can be used in conjunction with KYTC’s Data Driven Safety Analysis (DDSA) Implementation Guide to conduct highway safety analysis numerous KYTC processes. Historically, the Cabinet’s Division of Traffic Operations has occasionally requested this type of safety analysis. Now that CDAT is available, other business areas can realize benefits from advanced safety analysis. Recently, the Divisions of Planning and Design have collaborated with Traffic Operations to better understand how the HSM can be used in their routine functions. Moving forward, the DDSA Implementation Guide and CDAT will play an integral role in the Cabinet’s efforts to incorporate HSM methodology into its decision making. Additionally, CDAT can help maintain consistency across safety analyses. Often, KYTC staff and Kentucky Transportation Center (KTC) researchers perform analyses that result in dissimilar crash counts. Inconsistent results are common when queries are complex or rely on specific crash location information, when different tools or different data sets are used, or if staff have incomplete knowledge of crash coding

2019 Safety Belt Usage Survey in Kentucky

The objective of the survey summarized in this report was to establish a statewide safety belt usage rate in Kentucky for 2019. This rate can be compared to those determined from previous surveys. The 2019 statewide survey documents the continued effect associated with law enforcement, related education, and general public attitude

Development of an Improved Method for Determining Advisory Speeds on Horizontal Curves

Horizontal curves are an integral part of the highway alignment. However, a disproportionately high number of severe crashes occur on them. One method transportation agencies use to reduce the number crashes at horizontal curves is the installation of curve warning signs which post an appropriate advisory speed. Appropriate curve advisory speeds can be determined using several methods. Some of these methods are time-consuming to perform and are error-prone. The purpose of this research was to find the most efficient and accurate data collection method for determining curve advisory speeds. Several processes were developed and tested. They were then validated against the results of a manual process referred to as the Direct Method and other traditional methods (such as the ball-bank indicator), which are generally assumed to produce accurate results. Comparing the results of these methods allow researchers evaluate their accuracy and usefulness for setting advisory speeds. The results illustrate the potential of a more user-friendly methodology that allows for efficient and accurate data collection. The advisory speeds determined by this research will assist the Kentucky Transportation Cabinet to properly sign horizontal curves. Previous research suggests that posting appropriate advisory speeds results in a safer driving experience

2014 Safety Belt Usage Survey in Kentucky

The objective of the survey summarized in this report was to establish a statewide safety belt usage rate in Kentucky for 2014. This rate can be compared to those determined from previous surveys. The 2014 statewide survey continues to document the increase in usage associated with the change in the law to allow primary enforcement and related education and enforcement

2017 Safety Belt Usage Survey in Kentucky

The use of safety belts and child safety seats is a proven means of reducing injuries to motor vehicle occupants involved in traffic crashes. The objective of the survey summarized in this report was to establish a statewide safety belt usage rate in Kentucky for 2017. This rate can be compared to those determined from previous surveys. The 2017 statewide survey documents the continued increase in usage associated with the change in the law to allow primary enforcement and related education and enforcement

2018 Safety Belt Usage Survey in Kentucky

The objective of the survey summarized in this report was to establish a statewide safety belt usage rate in Kentucky for 2018. This rate can be compared to those determined from previous surveys. The 2018 statewide survey documents the continued increase in usage associated with the change in the law to allow primary enforcement and related education and enforcement