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Engineering

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Resources about highway and vehicle engineering solutions and performance in rural safety.

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Intersections

Noteworthy Practices

Guidelines for Using Centerline Rumble Strips in Virginia
Virginia Transportation Research Council

Safety Evaluation of Transverse Rumble Strips on Approaches to Stop-Controlled Intersections in Rural Areas (PDF)
Federal Highway Administration, 2012
Examines the impact of transverse rumble strips on crashes, specifically total crashes, injury crashes, and specific crash types.

Modern Roundabouts: A Safer Choice (Video [WMV, MOV])
Federal Highway Administration, 2010
This video discusses the safety, operational, environmental, and aesthetic benefits of roundabouts.

Evaluating Safety and Operation of High-Speed Intersections
Oregon Department of Transportation, Federal Highway Administration, 2010
FHWA-OR-RD-10-15
This report reviews a research effort to evaluate the safety and operations of high-speed intersections in the State of Oregon. In particular, this research effort focuses on four-leg, signalized intersections with speed limits of 45 mph or greater where the intersections are not in the immediate vicinity of other signalized intersections.

Comprehensive Intersection Resource Library
Federal Highway Administration, 2010
This Web site covers topics in five broad categories: traditional signalized intersections, traditional unsignalized intersections, roundabouts, highway/rail grade crossings, and alternative intersection designs such as single-point intersections.

Intersection Safety Implementation Plan Process
Federal Highway Administration, 2009
This document provides States a process for creating an implementation plan to guide intersection safety implementation activities. It is specifically targeted toward State Safety Engineers who have intersection safety as an emphasis area in their SHSP.

Safety at Unsignalized Intersections
Federal Highway Administration, 2009
This presentation on the topic of safety at unsignalized intersections covers the following topics: nature and magnitude of the problem, documents available to help with countermeasure selection, types of crashes, countermeasures and associated crash reduction factors.

Roundabouts (PDF)
Federal Highway Administration, 2010
FHWA-SA-10-006
This technical summary explores the characteristics of modern roundabouts while reinforcing the need to apply a principles-based approach to design.

Two Low-Cost Safety Concepts for Two-Way STOP-Controlled, Rural Intersections on High-Speed Two-Lane, Two-Way Roadways (PDF)
Federal Highway Administration, 2009

Key Intersection Safety Resources (PDF)
Federal Highway Administration (FHWA), 2008
Lists publications, training, and other resources available on the topic of intersection safety.

Crash Analysis of Roundabouts at High-Speed Rural Intersections (PDF)
Transportation Research Record No. 2096 (2009) [For TRR subscribers only]
This research conducted a safety analysis of 17 intersections on high-speed rural roadways in the United States that were converted to roundabouts. The findings show the average injury crash frequency was reduced by 84%, average injury crash rate was reduced by 89%, angle crashes were reduced by 86%, and fatal crashes were reduced by 100%.

Toolbox of Countermeasures and Their Potential Effectiveness for Intersection Crashes (PDF)
Federal Highway Administration, Institute of Transportation Engineers, 2007
Issue Brief 8
This issue brief documents estimates of the crash reduction that might be expected if a specific countermeasure or group of countermeasures is implemented with respect to intersection crashes. The crash reduction estimates are presented as Crash Reduction Factors (CRFs).

Guidelines for Selection of Speed Reduction Treatments at High-Speed Intersections (PDF)
Transportation Research Board, 2008
NCHRP Report 613
This report evaluates the effectiveness of treatments to reduce vehicle speeds at high-speed intersections.

Safety Effectiveness of Lane and Shoulder Width Combinations on Rural, Two-Lane, Undivided Roads (PDF)
Transportation Research Record No. 2103 (2009) [For TRR subscribers only]
There is a need to evaluate low-cost safety strategies that states may implement as part of their Strategic Highway Safety Plan. FHWA organized a pooled fund study of 26 states to evaluate several low-cost safety strategies, including the reallocation of total paved width. This study identifies whether it is safer to increase lane width or increase shoulder width given a fixed total width. Individual state results did not indicate a clear trade-off between lane and shoulder width for a fixed total width. Supplementing the results of this study with previous research, crash modification factors (CMFs) are provided for several lane-shoulder combinations. The selected values present a more apparent trade-off, indicating a slight benefit to increasing lane width for a fixed total width.

Impact of Some Site-Specific Characteristics on the Success of the Signalization of High-Speed Intersections (PDF)
Iowa State University, Ames; Iowa Department of Transportation, 2008

Strategies to Address Nighttime Crashes at Rural, Unsignalized Intersections (PDF)
Center for Transportation Research and Education, Iowa State University, 2008
IHRB Project TR-540, CTRE Project 05-220
Citizens request the installation of roadway lighting in their communities based on several motivations, including the experience or perception that lighting improves traffic safety and reduces crime, while also providing a tangible benefit of taxpayer dollars at work. Roadway authority staff fully appreciate these citizen concerns; however, roadway lighting is expensive to install, supply energy to, and maintain in perpetuity. The installation of roadway lighting is only one of a number of strategies agencies have to address nighttime crash concerns. This research assists local agencies in deciding when, where, and how much rural intersection lighting to provide.

Two Low-Cost Safety Concepts for Two-Way STOP-Controlled, Rural Intersections on High-Speed Two-Lane, Two-Way Roadways
Federal Highway Administration, 2008
FHWA-HRT-08-063
As a part of the FHWA efforts to reduce intersection crashes, two concepts have been identified: 1) rumble strips on outside shoulders and in a painted yellow median island on major road approaches and 2) channelizing separator islands on side road approaches with supplemental STOP signs.

Intersection Decision Support: An Overview
Minnesota Department of Transportation, 2007
MN/RC 2007-33
Discusses the four main research results of the Rural IDS research program. Rural Intersection Decision Support (IDS) focuses on enhancing the driver's ability to successfully negotiate rural intersections.

Braking Behavior at Rural Expressway Intersections for Younger, Middle-Aged, and Older Drivers (PDF)
University of Iowa, 2007
High speed expressway intersections can be problematic for drivers of all ages. The purpose of this study is to evaluate driver performance at a high crash rate rural expressway intersection for three age groups: older (65 to 80), younger (18 to 25), and middle-aged drivers (35 to 55). This study reports preliminary findings associated with 30 drivers (ten drivers in each age group) who participated in an instrumented vehicle study.

A Simulator-Based Evaluation of Smart Infrastructure Concepts for Intersection Decision Support for Rural Thru-STOP Intersections (PDF)
Minnesota Department of Transportation, 2007
MN/RC 2007-31
Describes the human factors basis for an intersection decision support (IDS) system intended to improve the safety of rural intersections in Minnesota’s Interregional Corridors (IRCs). The purpose of the human factors effort is to understand the task of rural intersection negotiation, identify high-risk user groups, describe the human factors that contribute to intersection accidents, and determine what conceptual types of information to present in the IDS display to improve driver performance and safety.

Safety Effects of Offset Right-Turn Lanes at Rural Expressway Intersections(PDF)
Iowa State University, 2007
Examines offset right-turn lane implementation at three two-way stop controlled rural expressway intersections and documents their safety performance using naive before-after crash data analysis. The results show that offset right-turn lanes can be effective in reducing the frequency of near-side right-angle collisions occurring at TWSC rural expressway intersections.

Stopping Behavior at Real-World Stop-Controlled Intersections with and without In-Lane Rumble Strips
Minnesota Local Road Research Board, 2006
Mn/DOT 2006-42
This was the third in a series of studies investigating various aspects of rumble strips.

Safety Impact of Street Lighting at Isolated Rural Intersections (PDF)
Minnesota Department of Transportation, 2004
Many Minnesota highway agencies do not routinely install or maintain streetlights at rural intersections or retain formal warrants or guidelines for installation. This study was initiated to evaluate the effectiveness of rural street lighting in reducing nighttime crashes at isolated rural intersections so that Minnesota agencies have more information to make lighting decisions.

Reducing Crashes at Controlled Rural Intersections
Minnesota Local Road Research Board, 2003
MN/RC 2003-15
This report is the culmination of a project intended to provide an initial exploration into ways to reduce crashes by manipulating the infrastructure.

Crash Models for Rural Intersections: Four-Lane by Two-lane Stop-Controlled and Two-lane by Two-lane Signalized(PDF)
Federal Highway Administration (FHWA), 1999
FHWA-RD-99-128
This report describes the collection, analysis, and modeling of crash and roadway data for intersections on rural roads in California and Michigan for the years 1993-1995.

Estimation of Safety at Two-way Stop-controlled Intersections on Rural Highways
Transportation Research Board, 1993
The application of the generalized linear modeling approach to the development of a model relating unsignalized intersection traffic demands to accident frequency is described. Several techniques for assessing model fit have been described and any inherent limitations noted.

Low-Cost Innovative Approaches to Improve Safety at Unsignalized Intersections on 4-Lane Divided Highways
Intersection crashes represent a significant portion of total crashes nationwide, accounting for an average of 9,000 fatalities and 1.5 million injuries annually. Without resorting to roundabouts or grade separations, there are a number of relatively low-cost approaches (either already in use in other countries or that could be developed) to improve the safety of unsignalized intersections on four-lane divided highways.


Barriers and Roadsides

Road Restraint Systems website
European Union Road Federation, 2012
A website dedicated to passive road safety systems and their use in the European Union.

Impact of Shoulder Width and Median Width on Safety
Transportation Research Board, 2009

Extended Road Shoulders on Rural Roads: A Measure for Cyclists and Pedestrians (PDF)
Norwegian Institute of Transport Economics, 2008

Safe and Aesthetic Design of Urban Roadside Treatments(PDF)
Transportation Research Board, 2009
NCHRP Report 612
Explores recommended design guidelines for safe and aesthetic roadside treatments in urban areas. The report also examines a toolbox of roadside treatments designed to balance pedestrian, bicyclist, and motorist safety and mobility.

Cross Median Crashes: Identification and Countermeasures
Minnesota Department of Transportation, 2008
Mn/DOT 2008-17
This report reviews the state-of-art with regard to identifying highway sections where median barriers would be most effective in preventing median-crossing crashes (MCC), and if necessary, develop remedies for any identified deficiencies.

Vegetation Control for Safety: A Guide for Local Highway and Street Maintenance Personnel (PDF)
Federal Highway Administration, 2008
FHWA FHWA-SA-07-018
Vegetation, if not controlled, can present a safety hazard for several reasons. Trees close to the road can present a fixed object hazard. Tall grass, weeds brush and tree limbs obscure or limit a driver's view of the road ahead, traffic control devices, approaching vehicles, wildlife and livestock, and pedestrians and bicycles. The purpose of this guide is to help local road agency maintenance workers identify locations where vegetation control is needed to improve traffic and pedestrian safety, to provide guidance for maintenance crews, and to make them aware of safe ways to mow, cut brush and otherwise control roadside vegetation.

A Guide to Standardized Highway Barrier Hardware
American Association of State Highway and Transportation Officials, American Road and Transportation Builder's Association, Association of General Contractors, 2005
AASHTO-AGC-ARTBA Task Force 13
A publication that provides specifications for both highway barrier hardware and systems. Includes barrier systems test level (TL) designation for various highway barrier applications. Also provides individual component details and specifications as well as system details.

Highway Safety and Trees: The Delicate Balance
Federal Highway Administration (FHWA), 2006
Everyone is a stakeholder when it comes to safety. Highway Safety and Trees: The Delicate Balance stresses that the design of highway projects should be a cooperative effort involving the highway agency, concerned communities, organizations, and individual citizens. Use this video to initiate a dialogue. The video provides an opportunity for all parties to recognize the benefits and risks associated with trees. It discusses many solutions from roadway relocation to use of guardrail to removal of trees from the most hazardous locations. It encourages highway agencies and the public to work together to improve safety while minimizing damage to the environment.

Barrier Guide for Low Volume and Low Speed Roads(PDF)
Federal Highway Administration (FHWA), 2005
FHWA-CFL/TD-05-009
This Guide is intended to provide assistance in the warranting, selection, and design of roadside barriers. The Guide is prepared specifically for warranting, selecting, and designing barriers on Federal Lands Highways projects that are low volume and/or low speed facilities. The guidelines present practical and useful guidance for common conditions and situations encountered in the design of roadside barriers for Federal Lands Highway projects.

Development of the Midwest Guardrail System (MGS) for Standard and Reduced Post Spacing and in Combination with Curbs (PDF)
Midwest Roadside Safety Facility, University of Nebraska-Lincoln, 2004
TRP-03-139-04
A new strong-post W-beam guardrail system called the Midwest Guardrail System (MGS) was developed, tested, evaluated, and provides increased safety for impacts with higher center-of-mass vehicles. The new barrier utilizes W-beam guardrail and standard W6x9 steel posts.


Treatments and Solutions

Design Guidance for High-Speed to Low-Speed Transition Zones for Rural Highways
Transportation Research Board, 2013

Implementing the High Risk Rural Roads Program
Federal Highway Administration, FHWA-SA-10-021, 2010
The High Risk Rural Roads Program (HRRRP) was established through the Highway Safety Improvement Program for construction and operational improvements on high risk rural roads. This report highlights common challenges to the HRRRP, lessons learned, and noteworthy practices shared by states.

Guidelines for Implementation of Cable Median Barrier
Transportation Research Board, 2010
This report provides a detailed examination of accidents in Kansas that determined the need for a cable median barrier.

Simulator Evaluation of Low-Cost Safety Improvements on Rural Two-Lane Undivided Roads (PDF)
Federal Highway Administration, 2010
FHWA-HRT-09-062
In this study, a driving simulator experiment was conducted to evaluate two sets of alternative low-cost safety improvements for rural areas. The first set of improvements was directed toward enhancing the visibility of curves on rural two-lane undivided roads at night.The second set of improvements was directed toward slowing traffic on rural two-lane undivided roads in small towns during the day by focusing on traffic calming within the towns.

Local Roads Safety Resource CD
Federal Highway Administration, 2010
The CD provides quick and easy access to the latest information on local roads safety. Organized by topic area in one place, the CD provides guidance, tools, and other resources from government agencies and national associations on local roadway safety.

Maintenance of Signs and Sign Supports - A Guide for Local Highway and Street Maintenance Personnel
Federal Highway Administration, 2010
This guide is intended to help local agency maintenance workers ensure their signs are maintained to meet this need.

Engineering Countermeasures for Reducing Speeds
Federal Highway Administration, 2009
This resource is a desktop reference of infrastructure improvements that can be implemented to lower speeds and their effectiveness.

Guidance for the Design and Application of Shoulder and Centerline Rumble Strips (PDF)
Transportation Research Board, 2009
NCHRP Report 641
Guidance for the Design and Application of Shoulder and Centerline Rumble Strips explores the design and application of shoulder and centerline rumble strips as a crash reduction measure, while minimizing adverse effects for motorcyclists, bicyclists, and nearby residents.

Safety Evaluation of Improved Curve Delineation (PDF)
Federal Highway Administration, 2009
FHWA-HRT-09-045
The goal of this research was to evaluate and estimate the effectiveness of improved curve delineation on rural two-lane undivided roads. This strategy is intended to reduce the frequency of crashes related to lack of driver awareness approaching curves as well as while navigating through curves by providing more conspicuous signing and lane markings.

Traffic Calming on Main Roads Through Rural Communities - TechBrief
FHWA, 2009
This TechBrief summarizes an evaluation of the effects on speed of low-cost, traffic-calming treatments on main rural highways passing through small, rural communities in Iowa. The full report, Appropriate Traffic Calming Techniques for Small Iowa Communities (TR-523), is available on Iowa State University 's Web site at: http://www.ctre.iastate.edu/research/detail.cfm?projectID=-226410767.

Traffic Calming for High-Speed Rural Roadways (PDF)
Minnesota Department of Transportation, 2008

Maintaining Traffic Sign Retroreflectivity
The FHWA Nighttime Visibility Web site includes the text of the final rule for maintained sign retroreflectivity, the changes to the MUTCD text, a brochure that explains the changes, training materials, and other related items. The final rule provides additional requirements, guidance, clarification, and flexibility in maintaining traffic sign retroreflectivity that is already required by the MUTCD. The minimum retroreflectivity levels and maintenance methods consider changes in the composition of the vehicle population, vehicle headlamp design, and the demographics of drivers.

Roadway Departure Safety Web site
Federal Highway Administration, 2008
This Web site provides highway designers, decision makers, and practitioners with information and guidance that will lead to safer roads and roadsides, with the priority of keeping drivers on the road.

Evaluation of Rumble Stripes on Low-Volume Rural Roads in Iowa: Phase I (PDF)
Center for Transportation Research and Education, Iowa State University, 2009
IHRB Project TR-577
The research described in this report evaluated the effectiveness of “rumble stripes” in reducing run-off-road crashes and in improving the longevity and wet weather visibility of edge line markings.

Driving Down Lane-Departure Crashes: A National Priority (PDF)
American Association of State Highway and Transportation Officials, 2008
Progress has been made over the past 25 years to reduce the highway traffic accident fatality rate from 2.76 fatalities per 100 million vehicle miles traveled in 1982 to 1.41 in 2006. However, while this is a major improvement, there are still about 42,000 deaths every year in the United States due to highway traffic accidents. Almost 60 percent of these fatalities involve vehicles leaving their lane and crashing and, of these, more than half result from vehicles leaving the road and rolling over or hitting fixed objects, such as utility poles or trees. Recognizing the need to address this challenge, national safety leaders gathered together in 1996 to develop a strategic plan for saving lives and preventing injuries.

Evaluation of the Effectiveness of Pavement Rumble Strips (PDF)
Kentucky Transportation Center, 2008
KTC-08-04 / SPR319-06-1F
This report analyzes the effectiveness of continuous shoulder rumble strips (CSRS) and centerline rumble strips (CLRS) on rural two lane roads in Kentucky. This study evaluates the safety benefits, and design details associated with the application of the CSRS and CLRS. The recommended practices proposed as a result of the crash analysis have the potential to reduce both run off the road and opposite direction crashes on rural two lane roads in Kentucky. These recommendations provide benefits for narrow roadways with little to no shoulder as well as larger roadways with wider paved shoulders.

Toolbox of Countermeasures and Their Potential Effectiveness for Roadway Departure Crashes (PDF)
Federal Highway Administration, 2007
FHWA-SA-07-013
This issue brief documents estimates of the crash reduction that might be expected if a specific countermeasure or group of countermeasures is implemented with respect to roadway departure crashes and other non-intersection crashes. The crash reduction estimates are presented as Crash Reduction Factors (CRFs).

Safety Benefits of a Road Departure Crash Warning System (DVD)
Transportation Research Board, 2008
Transportation Research Board Annual Meeting 2008 Paper No. 08-1656
More than 1.2 million road-departure crashes occur in the United States annually and these crashes often involve collisions with fixed objects or rollovers. According to 2004 statistics, although collisions with fixed objects or rollovers accounted for only 19 percent of all police-reported crashes, they accounted for 43 percent of the fatal crashes. To reduce road-departure crashes, the United States Department of Transportation (USDOT) allocated funding to develop and evaluate a Roadway Departure Crash Warning System (RDCW), which alerts drivers of impending lane or road departure. The Volpe National Transportation Systems Center carried out an independent evaluation of the RDCW using data collected in a field operational test (FOT). Safety benefits analysis, the topic of this paper, revealed that when the RDCW was activated drivers had fewer departure conflicts (close calls). Projections based on the FOT data indicate that with full national deployment and 100 percent system availability, approximately 9,400-74,800 fewer road-departure crashes would occur each year in the United States.

Analysis of Run-Off-Road Crashes in Relation to Roadway Features and Driver Behavior (PDF)
Iowa State University, 2007
The state of Wisconsin has been collecting crash information for the entire state trunk highway system that covers over 11,000 miles of roadways. This study examined crashes that occurred between 1998 and 2002, located based on a state-developed linear referencing system. A method (PRÈCIS), originally developed to systematically identify crashes on undivided state trunk highways (STH) and compute crash rates, crash densities (crashes/mile), and other safety statistics at any given point along a STH using a floating highway segment, was utilized. The study expanded the PRÈCIS application to divided highways and established relationships between driver actions that lead to a run-off-road crash and roadway information collected from the State Trunk Network log database.

Estimating Safety Benefits of Shoulder Rumble Strips on Two-Lane Rural Highways in Minnesota: Empirical Bayes Observational Before-and-After Study (PDF)
Transportation Research Board, 2007
Transportation Research Record: Journal of the Transportation Research Board No. 2019
Approximately 40% of all 2004 fatal crashes were single-vehicle, run-off-the-road (SVROR) crashes. The problem was even more significant on two-lane rural roads, where shoulder rumble strips were an important treatment in the prevention of these crashes and have proved effective on freeways. However, no studies have evaluated the effectiveness of shoulder rumble strips in reducing SVROR crashes on two-lane rural highways. An empirical Bayes before-and-after study was performed to evaluate the safety-effectiveness of milled-in continuous shoulder rumble strips on two-lane rural highways in Minnesota. The treatment was installed at 23 treatment sites (183 mi). This study reports a 13% reduction in all SVROR crashes and an 18% reduction in injury-producing SVROR crashes after installation of this treatment.

Evaluating the Effectiveness of Continuous Shoulder Rumble Strips in Reducing Single-Vehicle Ran-Off-Roadway Crashes in Nevada (PDF)
Iowa State University, 2007
Single-vehicle ran-off-roadway crashes are of significant concern in Nevada. This paper summarizes some findings of a research project to evaluate the effectiveness of continuous shoulder rumble strips to reduce such crashes in Nevada. The efforts evaluated safety records on roadways in Nevada on which continuous shoulder rumble strips had been installed. Analyses of the data showed that overall the continuous shoulder rumble strips treatment has been effective in reducing the frequency of single vehicle ran-off-roadway crashes and the corresponding crash rates.

Guidance for Implementation of the AASHTO Strategic Highway Safety Plan: Volume 20: A Guide for Reducing Head-On Crashes on Freeways (PDF)
Transportation Research Board, 2008
NCHRP Report 500
The American Association of State Highway and Transportation Officials (AASHTO) has adopted a national highway safety goal of halving fatalities over the next 2 decades—or reducing the number of fatalities by 1,000 per year. This goal can be achieved through the widespread application of low-cost, proven countermeasures that reduce the number of crashes on the nation's highways. This twentieth volume of NCHRP Report 500: Guidance for Implementation of the AASHTO Strategic Highway Safety Plan provides strategies that can be employed to reduce head-on crashes on freeways. The report will be of particular interest to safety practitioners with responsibility for implementing programs to reduce injuries and fatalities on the highway system.

Changeable Message Sign Displays During Non-Incident, Non-Roadwork Periods
Transportation Research Board, 2008
NCHRP Synthesis 383
This synthesis focuses on using Changeable Message Signs (CMSs) to display types of messages other than real-time messages for non-recurrent, environmental, special event traffic, and other special problems, as well as AMBER alerts, during non-incident/ non-roadwork periods as an alternative to leaving the CMS blank.

Use of Edge Line Markings on Rural Two-Lane Roadways (PDF)
Kentucky Transportation Center, University of Kentucky, 2008
KTC-08-02/SPR330-07-1I
The objective of this study was to review roadway characteristics and crash data in Kentucky and determine if revisions should be made to current guidelines for the use of edge lines. Recommendations were made concerning the use of edge lines, centerlines, and paved shoulders on rural, two-lane roadways with varying pavement widths.

Color Effectiveness of Yellow Pavement Marking Materials
Transportation Research Board, 2008
Research Results Digest 328
This digest explores range of chromaticity coordinates that observers classify as yellow and white under daytime and incandescent illumination.

Applications of Illuminated, Active, In-Pavement Marker Systems (PDF)
Transportation Research Board, 2008
NCHRP Synthesis 380
Illuminated, active, in-pavement marker systems (IPMs) can provide a greater level of information to road users than conventional pavement marker systems. This synthesis explores the state of IPM technology, experiences with IPM applications, and potential IPM research needs.

Passing Sight Distance Criteria
Transportation Research Board, 2008
NCHRP Report 605
This report presents recommendations on the adequacy of current procedures and guidelines used to estimate minimum passing site distance (PSD) requirements for highway design and pavement marking.

Four-Lane to Three-Lane Conversion Case Study: State Highway Through a Small Town
Video presentation by Keith Knapp, Center for Excellence in Rural Safety (University of Minnesota), March 2008
Four-lane undivided highways passing through small towns often have poor safety records, characterized by collisions between left-turning vehicles and oncoming traffic in the opposite lanes. Converting to three lanes with a central two-way turn lane is one solution frequently considered by transportation agencies. But while conversion to three lanes can provide advantages to local stakeholders, Keith Knapp cautioned that careful planning is necessary to carry out a successful conversion.

To help ensure a successful conversion, Knapp said, it is important to match the highway cross-section to the traffic flow characteristics. If the two center lanes of a four-lane undivided roadway are already being used primarily for left turns, for example, converting to a three-lane cross section may result in a safety improvement without much loss of mobility However, if traffic flow is dominated by through traffic with few turning vehicles, a conversion may not yield appreciable benefits.

Additional information on conversions is available in Safety and Operational Characteristics of Two-Way Left Turn Lanes (Mn/DOT 2006-25) (PDF 2.2 MB) and the Iowa DOT’s Guidelines for the Conversion of Urban Four-Lane Undivided Roadways to Three-Lane Two-Way Left-Turn Lane Facilities (PDF 630 KB).

Horizontal Curve Signing Handbook (PDF)
Texas Transportation Institute, 2007
TxDOT Report 0-5439-P1
The procedures described in this handbook are intended to improve consistency in curve signing and driver compliance with the advisory speed. The handbook describes guidelines for determining when an advisory speed is needed, criteria for identifying the appropriate advisory speed, an engineering study method for determining the advisory speed, and guidelines for selecting other curve-related traffic control devices. A procedure spreadsheet (xls) is available.

Low Cost Local Road Safety Solutions
The American Traffic Safety Services Association, 2006
Tool to help local jurisdictions focus on proven low cost safety solutions.

Low-Cost Treatments for Horizontal Curve Safety, 2006
Federal Highway Administration (FHWA), 2006
FHWA-SA-07-002
Provides practical information on low-cost treatments that can be applied at horizontal curves to address identified or potential safety problems.

Good Practices: Incorporating Safety into Resurfacing and Restoration Projects
Federal Highway Administration (FHWA), 2006
FHWA-SA-07-001
The report identifies a set of common issues host agencies confronted in developing integrated resurfacing-safety improvement programs, and also observed a set of common success factors

Preliminary Evaluations of Safety Treatments on Rural Highways in Texas (PDF)
Texas Department of Transportation, 2004
FHWA/TX-05/0-4048-5
Focuses on before-and-after evaluations of safety treatments installed between 1995 and 2000 at 50 locations on rural highways in Texas.

Roadway Safety Tools for Local Agencies
Transportation Research Board, 2004
NCHRP Synthesis 321
Provides an overview of tools for local governments, including how to develop a Local Safety Improvement Program

Low-Cost Innovative Approaches to Improve Safety at Unsignalized Intersections on 4-Lane Divided Highways
Intersection crashes represent a significant portion of total crashes nationwide, accounting for an average of 9,000 fatalities and 1.5 million injuries annually. Without resorting to roundabouts or grade separations, there are a number of relatively low-cost approaches (either already in use in other countries or that could be developed) to improve the safety of unsignalized intersections on four-lane divided highways.

ITE: Traffic Calming
Web site developed by the Institute of Transportation Engineers with support from FHWA. Contains information about calming measures, as well as seminar materials, reports, and discussions.

Traffic Calming in Minnesota
Minnesota Local Road Research Board,
Web site developed for the Minnesota Local Road Research Board (LRRB), containing a searchable database of traffic calming projects implemented in Minnesota and traffic calming data collection guidelines


Analysis and Performance

Crash Modification Factors Clearinghouse
Federal Highway Administration, 2010
A crash modification factor (CMF) is a multiplicative factor used to compute the expected number of crashes after implementing a given countermeasure at a specific site. The Crash Modification Factors Clearinghouse houses a database of CMFs along with supporting documentation to help transportation engineers identify the most appropriate countermeasure for their safety needs.

Applicability of FHWA Crash Prediction Module to Selecting Candidate Locations for Safety Audits of Two-Lane Rural Highways (PDF)
Transportation Research Board, 2009
Transportation Research Record: Journal of the Transportation Research Board No. 2137
The Interactive Highway Safety Design Model (IHSDM) is a suite of software developed by FHWA for monitoring and analyzing two-lane rural highways in the United States. IHSDM consists of six modules: Policy Review, Crash Prediction (CPM), Design Consistency, Traffic Analysis, Intersection Review, and Driver/Vehicle. Of the six modules, CPM was selected for possible use in safety audits of two-lane rural highways. The study concludes that CPM could be useful for engineering decision making during safety audits of two-lane rural highways. Interpreting the outputs from CPM, however, requires knowledge and experience in highway design.

Evaluating Effectiveness of Dynamic Speed Display Signs in Transition Zones of Two-Lane, Rural Highways in Pennsylvania
Transportation Research Board, 2010
Although law enforcement is an effective way to manage speeds, it requires significant resources to ensure adequate spatial and temporal compliance. A before, during, and after observational study of free-flow vehicle operating speeds was undertaken at 12 transition zones to determine the effectiveness of dynamic speed display signs (DSDSs).

Safety Evaluation of Improved Curve Delineation
Federal Highway Administration, 2009
FHWA-HRT-09-045
The goal of this research was to evaluate and estimate the effectiveness of improved curve delineation on rural two-lane undivided roads. This strategy is intended to reduce the frequency of crashes related to lack of driver awareness approaching curves as well as while navigating through curves by providing more conspicuous signing and lane markings.

Relationship between Road Geometry, Observed Travel Speed, and Rural Accidents
Land Transport New Zealand, 2009

Interactive Highway Safety Design Model
Federal Highway Administration, 2008
Version 5.0.0
The 2008 public release (Version 5.0.0) of Interactive Highway Safety Design Model (IHSDM) is available for free downloading at www.ihsdm.org. The existing 2007 IHSDM is a suite of software analysis tools for evaluating safety and operational effects of geometric design decisions on two-lane rural highways. It includes five evaluation modules: policy review, crash prediction, design consistency, intersection review, and traffic analysis. The 2008 release includes the addition of a fully functioning beta version of a driver/vehicle module (DVM) as well as significant enhancements to output/reporting capabilities, the evaluation process/wizard, the graphical user interface (GUI), data handling, the highway editor, accessibility features, help/documentation, and the administration tool. The DVM is a computational model of driver behavior that simulates the driver's perceptual, cognitive, and control processes to generate steering, braking, and acceleration inputs to the vehicle.

Cost Effective Safety Improvements for Two-Lane Rural Roads (PDF)
Federal Highway Administration (FHWA), 2008
TNW2008-04
This study focuses on accident analysis of two-lane rural roads in Washington State. Results from the statistical analyses and accident risk models not only help identify accident causal factors, but also provide valuable insights for developing countermeasures against two-lane rural road traffic accidents.

Evaluation of the Applicability of the Interactive Highway Safety Design Model to Safety Audits of Two-Lane Rural Highways
Utah Department of Transportation, 2008
UT-08.02
This report explores the crash prediction and intersection review modules included in the FHWA's Interactive Highway Safety Design Model.

Methodology to Predict the Safety Performance of Rural Multilane Highways (PDF)
TRB’s National Cooperative Highway Research Program (NCHRP) Web-Only Document 126, 2008
Explores a methodology designed to predict the safety performance of various elements considered in the planning, design, and operation of nonlimited-access rural multilane highways.

Evaluation of the Use and Effectiveness of Wildlife Crossing
Transportation Research Board, 2008
NCHRP Report 615
This report documents the development of an interactive, web-based decision guide protocol for the selection, configuration, and location of wildlife crossings.

Prediction of the Expected Safety Performance of Rural Two-Lane Highways
Federal Highway Administration (FHWA), 1999
FHWA-RD-99-207
This report presents an algorithm for predicting the safety performance of a rural two-lane highway.

Accident Models for Two-Lane Rural Roads
Federal Highway Administration (FHWA) Office of Safety and Traffic Operations R&D, 1998
FHWA-RD-98-133
The Accident Analysis Module is expected to estimate the safety of two-lane rural highway characteristics for existing and new projects.

Accident Modification Factors for Traffic Engineering and ITS Improvements
Transportation Research Board, 2008
NCHRP Report 617
This report explores the development of accident modification factors (AMFs) for traffic engineering and intelligent transportation system improvements. AMFs, also known as crash reduction factors, are designed to provide a simple and quick way of estimating the safety impacts of various types of engineering improvements, encompassing the areas of signing, alignment, channelization, and other traffic engineering solutions.

Effect of Resurfacing on Safety of Two-Lane Rural Roads in New York State
Transportation Research Board, 1994
In the early 1980s, two kinds of resurfacing projects were undertaken in New York State: Fast track projects involving only resurfacing, and reconditioning and preservation (R&P) projects in which roadside and roadway safety improvements have been incorporated with resurfacing. The question was whether following resurfacing the fast track projects [226.7 mi (364.8 km)] perform less well, from a safety viewpoint, than the R&P projects [137.2 mi (220.8 km)]. Findings indicated that in fast track projects safety initially declined, but in R&P projects safety improved. Another conclusion that emerges from this work is that, within the first 6 to 7 years of pavement life, safety improves as the pavement ages. The Empirical Bayes approach to the study of the safety effect has been used.

Highway Safety Challenges on Low-Volume Rural Roads
Federal Highway Administration (FHWA)
This paper analyzes the crash occurrence and potential safety treatments on low-volume rural roads.

Interactive Highway Safety Design Model (IHSDM)
The IHSDM Library includes all recently published materials on IHSDM in electronic and/or hard copy format.


Other

FHWA Road Safety Audit Guidelines
Federal Highway Administration (FHWA), 2005
FHWA-SA-06-06
Provides a foundation for public agencies and Tribal Governments in the U.S. to draw upon when developing their own road safety audit policies and procedures and when conducting road safety audits within their jurisdictions.

RSA Newsletter
Federal Highway Administration, 2008
RSA newsletter provides current information on road safety audits. This issue contains: RSA Snapshots, Quarterly Highlights, Safety Policy Memorandum Provision on RSAs, TRB, NHI, and Utah LTAP News, Upcoming Event: NHI RSA Web Conference.

Pedestrian Safety on Rural Highways (PDF)
Federal Highway Administration (FHWA), 2004
FHWA-SA-04-008
The research described in this paper sought to identify the characteristics of rural pedestrian fatalities in ten states with above-average rates of rural pedestrian fatalities.

Forward Looking Blindspots: A report of A-Pillar induced field-of-view obstruction and driver performance in a simulated rural environment
Minnesota Local Road Research Board, 2002
Mn/DOT 2002-16
This study analyzed the relationship between the size of the forward looking blindspot (FLB) produced by vehicles A-post (windshield frame), the speeds of two vehicles approaching an intersection at right angles, and driver behavior relative to a likely accident event.

 

Center for Excellence in Rural Safety | University of Minnesota | Minneapolis, MN 55455 | Location & Contact Information