ESTIMATION OF ANNUAL AVERAGE DAILY TRAFFIC ON LOCAL ROADS IN KENTUCKY

Annual average daily traffic (AADT) is used to estimate intersection performance across Kentucky. The Kentucky Transportation Cabinet (KYTC) currently collects AADTs for state maintained roads, but lacks this information on local roads. A method is needed to estimate local road AADTs in a cost-effective and reasonable manner. A literature review was conducted on AADT models and found no models suitable to Kentucky. Therefore an AADT model using non-linear regression was developed for local roads in Kentucky This model divided the state into three regions utilizing Kentucky’s highway districts. This partitioning accounted for geographic and socioeconomic variability across the state. Each regional model relied upon three independent variables: probe count, residential vehicle registration, and curve rating. HERE proprietary probe counts provide tracking visibility on a select portion of vehicles moving across Kentucky highways. Residential vehicle registrations were used to estimate trip generation information. Finally, the curve rating partially indicates accessibility. The models were adjusted to KYTC daily vehicle miles traveled (DVMT) county control totals for local roads. Sensitivity analysis was conducted to examine the impact of model errors for use in intersection safety analysis. Results indicate that the estimates generated can be effectively used for safety assessment and countermeasure prioritization

Application of IHSDM: KY 30 Case Study

A section of KY 30 in Jackson and Owsley Counties is targeted for redesign to provide a safer and more efficient corridor that will support economic activity in eastern Kentucky. Data for the existing KY 30 alignment and eight alternative alignments developed by HMB Professional Engineers Inc. were provided to researchers at the Kentucky Transportation Center (KTC). KTC researchers also developed a new alternative that modified the existing alignment to improve the safety of various locations. Researchers applied safety analysis procedures from Part C of the Highway Safety Manual (HSM) to the existing and alternative alignments of KY 30 using the Interactive Highway Safety Design Model (IHSDM). The resulting crash predictions were used to analyze each alternative and perform a benefit-cost analysis. Each alignment’s safety benefits were derived by calculating the total reduction in crashes (i.e., subtracting the number of crashes anticipated for an alternative from the number of crashes that would be expected if the segment were not redesigned). Comprehensive crash costs from the National Safety Council (NSC) were applied to the reduction in crashes to estimate, in monetary terms, the safety benefit. This figure was compared to the estimated cost of each project. KTC’s modified existing alignment had a benefit-cost (B/C) ratio of 0.14, meaning project’s cost outweighs the expected safety benefits. The other new build alternatives had negative B/C ratios, meaning the cost of crashes is expected to increase after their implementation. The increase in crash costs for the new build alternatives is due to the increase in crash severity expected on the new alignments coupled with the current alignment remaining a source of crashes (as the latter would remain open to facilitate the mobility of residents). IHSDM analysis only captures expected safety benefits, however. The selected alternative may be economically justifiable based on a holistic evaluation of the potential benefits it offers — in addition to safety benefits. The potential non-safety benefits of each project alternative should be analyzed to inform and improve the decision-making process for the KY 30 redesign

Evaluation of Guardrail Needs and Update of Guardrail Rating Program

The Kentucky Transportation Cabinet (KYTC) seeks to reduce the frequency of roadway departure crashes, which often prove fatal. Roadside barriers such as guardrail have proven effective at mitigating these crashes, however, the demand for installations is high throughout the state. KYTC must prioritize prospective guardrail locations to match available funds with the most critical, or unsafe, sites. The current guardrail rating program (GRP) was established in 1989 to identify and prioritize guardrail needs. Despite periodic updates, the existing program no longer meets the transportation industry’s safety guidelines and policies. The Kentucky Transportation Center (KTC) studied national and state guardrail practices and developed a new methodology for prioritizing guardrail installations. The new GRP model focuses on two main factors: crash frequency and crash severity, with the goal of maximizing safety outcomes for roadway departure crashes

Evaluation of Alternative Rumble Strip Designs

Since Kentucky’s initial rumble strip designs were adopted, there has been additional research and experimentation in other states with alternative designs as a response to complaints from the public about noise pollution caused by rumble strips. The new research indicates that other rumble strip designs might provide increased interior noise/vibration with decreased exterior noise. Application of these alternative designs in Kentucky could result in improved rumble performance, reduced damage to new pavement, decreased noise pollution, installation on roadways with lower speed limits, and allow reinstallation of rumbles on thin overlays/microsurfacing. The research team reviewed national and state guidelines for conventional and alternative rumble strip designs and compiled a synthesis of current rumble strip practices. A series of site visits to rumble strip installations across the state revealed many findings about Kentucky’s current rumble strip practices. This research provides recommendations for conventional, sinusoidal, and shallow rumble strips as well as for rumble strip maintenance, rumble strips on thin overlays, and the use of edgeline and centerline rumble strips

KYTC Sidewalk and Curb Ramp Inventory for ADA Compliance

The Americans with Disabilities Act of 1990 (ADA) requires that all public and private organizations providing services to the public ensure their facilities and infrastructure comply with regulations set forth therein. The ADA requires that a transition plan “identify physical obstacles in the public entity’s facilities that limit the accessibility of its programs or activities to individuals with disabilities.” In the first phase of Kentucky’s transition plan to become ADA compliant, KTC researchers inventoried sidewalks along all state-maintained roads in Kentucky to determine the presence or absence of pedestrian facilities. This sidewalk inventory was used to query Kentucky’s intersection database to achieve two goals: identify intersections along state-maintained roadways that have sidewalks, and determine the presence of curb ramps at intersections. Researchers performed quality control to ensure sidewalk and curb ramp inventories correctly characterized the pedestrian facilities that existed on the roadways. This process showed the error in the inventory to be approximately five percent, below the 10 percent error rate requested by KYTC. As a result of this project, KYTC now has access to a statewide inventory of state-maintained sidewalks and curb ramps that can serve as the basis for Kentucky’s ADA compliance transition plan

Evaluation of Roadway Lighting Practices

Adequate roadway lighting allows better driver visibility during nighttime conditions. Research studies show that lighted roadways on average experience 28 percent fewer vehicles crashes on all roadway types. Most state DOTs have historically used High-Pressure Sodium (HPS) lights for their roadside lighting programs due to their wide availability and relatively low purchase costs. However, the short lifespan of HPS results in frequent replacement, leading to high life cycle costs. Light-Emitting Diode (LED) lights consume less energy, demonstrate improved performance, and require less overall maintenance due to their longer lifespans. Over time, this translates into maintenance cost savings for stateDOTs. In recent years, several state and local governments have begun increasing their use of LED lighting. KTC reviewed other state’s best practices for roadway lighting and assisted KYTC with analyzing the performance differences between HPS and LED. KTC also compiled a statewide roadside lighting inventory through coordination with each KYTC district.After developing the full inventory, the research team conducted light surveys at locations across Kentucky. The light surveys confirmed that LED lights routinely outperform HPS lights. It is recommended that Kentucky continue to transition to LED lighting, find a method for keeping the statewide lighting inventory up to date, and specify light spacing for new installations

Coaxing HIS Data from Mandli Pavement Scans

The Kentucky Transportation Cabinet (KYTC) Division of Planning’s Highway Information Systems (HIS) database provides geometric information about horizontal and vertical curves, but its accuracy is unknown. An updated method of pavement analysis collects data by scanning the pavement as a van equipped with Mandli software drives the area of interest. The scans provide detailed information that can be used to calculate roadway geometry characteristics (e.g., curve radius, cross slope/superelevation, and grade). This study evaluated the ability of the Mandli data to support curve advisory calculations and find a way to utilize Mandli data to improve the existing HIS database. To this end, the report includes a literature review to determine applicability of data, a series of data validation steps to define Mandli’s accuracy, and an evaluation of tools that convert Mandli into usable HIS data. The data attributes of focus are horizontal curve radius, grade, and cross slope. Horizontal curve radii values were evaluated using University of Nevada Reno’s ArcMAP plugin, Florida DOT’s curvature extension tool, and the University of Kentucky’s Curvature Automatic Tool (UKCAT). These tools were tested for usability, efficiency, and accuracy. Vertical curve attributes, including grade and cross slope, were evaluated by comparing Mandli data to manual field measurements, design plans, and other data collection methods. After data collection and analysis, researchers outline a newly developed method for converting Mandli data into a usable form and implementing it in HIS

In-Service Evaluation of High Tension Cable Barrier Systems

The Kentucky Transportation Cabinet has installed hundreds of miles of high-tension cable median barrier (CMB) as a safety innovation. The usage of CMB aids in the prevention of crossover crashes, where a vehicle departs the roadway on the left shoulder, crosses the median, and enters the opposing lane(s) of traffic. KYTC officials have questioned whether all three barrier products perform similarly. Some installed cable barrier systems have lost tension across the entire cable length after a single vehicle impact. If a second vehicle were to strike the cable barrier system in a location other than the damaged area of the first vehicle’s crash, ideally, the high-tension cable barrier system should continue to prevent errant vehicles from crossing the median and causing a head-on collision. The goal of this research was to improve the safety and effectiveness of Kentucky’s cable barrier systems by reviewing state DOT best practices for cable barrier, conducting on-site evaluation of current cable barrier installations, and examining crash data. The research team analyzed each CMB vendor product’s performance and maintenance requirements, and recommended modifications to KYTC policies, specifications, and maintenance procedures. The study showed that CMB systems have decreased crossover crashes in Kentucky, which warrants the continued use of high-tension cable barrier across the state. One recommendation of the study is to institute and enforce tension-monitoring programs, as applicable, for both annual inspections and after repairs

Estimation of Average Daily Traffic on Local Roads in Kentucky

Kentucky Transportation Cabinet (KYTC) officials use annual average daily traffic (AADT) to estimate intersection performance across the state maintained highway system. KYTC currently collects AADTs for state maintained roads but frequently lacks this information on local roads. A method is needed to estimate local road AADTs in a cost-effective and reasonable manner. Kentucky Transportation Center (KTC) researchers conducted a literature review on U.S. AADT models but found that none of them were suitable to Kentucky. Therefore, KTC developed an AADT model using non-linear regression to estimate AADTs on approaches to those intersections. KTC developed a Poisson distributed, non-linear regression model to estimate AADT. This model divided the state into three regions encompassing all of the highway districts: West (Districts 1, 2, 3, and 4), North Central (Districts 5, 6, and 7), and East (Districts 8, 9, 10, 11, and 12). This partitioning accounted for geographic and socioeconomic variability across the state. Each regional model relied upon three independent variables: probe count, residential vehicle registration, and curve rating. HERE proprietary probe counts—indicative of vehicle movements—provide tracking visibility on a select portion of vehicles moving across Kentucky highways. Residential vehicle registrations can be used to estimate trip generation information. Finally, the curve rating partially indicates accessibility. Model results were adjusted to KYTC daily vehicle miles traveled (DVMT) county control totals for local roads. Sensitivity analysis was conducted to examine the impact of model errors for use in intersection safety analysis. Results indicate that the estimates generated can be effectively used for safety assessment and countermeasure prioritization

Improvement of Fatal Crash Analysis and Follow-Up

Executive Summary Fatalities resulting from traffic crashes in Kentucky increased from a low of 638 in 2013 to 834 in 2016 (a 31% increase), and there is not a full understanding of the underlying causes for this trend. This study analyzes fatal crashes using data from both Kentucky’s crash reports and the National Highway Traffic Safety Administration’s (NHTSA) Fatal Accident Reporting System (FARS) to identify countermeasures to combat increasing fatal crash rates. In addition, this study compares Kentucky’s crash reports to the fatal crash data in FARS to identify data inconsistencies and recommend procedures to eliminate these inconsistencies. Emphasis was placed on fatal crashes involving alcohol and drugs because police-reported crash data in Kentucky do not clearly represent the magnitude of alcohol- and drug-related fatal crashes. More detailed analysis of fatal crashes involving alcohol and drugs provides an understanding of the patterns of impaired drivers in terms of their overall characteristics, crash locations, time of day, types of drugs, and other identifying factors that affect patterns and behavior. The study identified crashes involving mature drivers (65+) and lane departure crashes as fatal crash types with the greatest increases since 2013. Pedestrian, motorcycle, intersection, and impairment-related fatal crashes also demonstrated increasing fatal crash rates in 2016. Analysis of restraint use showed that almost 54% of the fatally injured people in 2016 were not wearing a seatbelt when one was available to them. Of those fatally injured in a motorcycle crash, nearly 72% were not wearing a helmet. Based on FARS data, there were 160 fatal crashes in Kentucky in which a driver tested positive for alcohol and 266 fatal crashes where a driver tested positive for at least one drug. The drugs most frequently found in drivers were tetrahydrocannabinol (THC), hydrocodone, and Xanax. In general, fatal crash frequency spiked during the morning and afternoon peak hour periods, with fatalities occurring more frequently between 11 am and 11 pm. The percent of potentially impaired (alcohol- and drug-involved) fatal crashes increased between 5 pm and 4 am from around 40% to a peak of 81% at 4 am. Eastern Kentucky was identified as a region with high fatal crash rates and potentially impaired fatal crash rates. Both Ballard and Union Counties in Western Kentucky showed high fatality and potentially impaired fatality rates as well. Comparisons between the FARS database and Kentucky’s crash reports revealed inconsistencies between the date, time, location, injury severity, and impairment indications in the two databases. Recommendations stemming from this study were divided into four categories: enforcement, legislation/licensing, public involvement, and data collection. The recommendations are aimed at reducing crash fatalities, improving crash data collection, and improving consistency between Kentucky’s crash reports and the national FARS database