Synthesis of Iowa Research to Address Rural Safety, RB04-013, 2014

Information about roadway departures, rural intersections, and rural speed management countermeasures relevant to Iowa was summarized on webpages (www.ctre.iastate.edu/research-synthesis/) to allow agencies to more effectively target specific types of crashes in Iowa. More information about each of the countermeasures described in this tech transfer summary, as well as speed impacts, reported crash modification factors, costs, usage within Iowa, and Iowa-specific guidance, is available on the Synthesis of Safety-Related Research web pages at www.ctre.iastate.edu/research-synthesis/. The project provides Iowa agencies with a resource (both web pages and relevant publications) to address rural safety. The team is coordinating with the Iowa Local Technical Assistance Program (LTAP), the Iowa Highway Research Board, the Iowa Association of Counties, and other groups to explore additional ways to distribute the information to local and county agencies.

Lane-Departure Safety Countermeasures: Strategic Action Plan for the Iowa Department of Transportation, 2011

Lane departure crashes are the single largest category of fatal and major injury crashes in Iowa. The Iowa Department of Transportation (DOT) estimates that 60 percent of roadway-related fatal crashes are lane departures and that 39 percent of Iowa’s fatal crashes are single-vehicle run-off-road (SVROR) crashes. Addressing roadway departure was identified as one of the top eight program strategies for the Iowa DOT in their Comprehensive Highway Safety Plan (CHSP). The goal is to reduce lane departure crashes and their consequences through lane departure-related design standards and policies including paved shoulders, centerline and shoulder rumble strips, pavement markings, signs, and median barriers. Lane-Departure Safety Countermeasures: Strategic Action Plan for the Iowa Department of Transportation outlines roadway countermeasures that can be used to address lane departure crashes. This guidance report was prepared by the Institute for Transportation (InTrans) at Iowa State University for the Iowa DOT. The content reflects input from and multiple reviews by both a technical advisory committee and other knowledgeable individuals with the Iowa DOT.

Design, Construction, and Field Testing of an Ultra High Performance Concrete Pi-Girder Bridge, TR-574, 2011

Among the variety of road users and vehicle types that travel on U.S. public roadways, slow moving vehicles (SMVs) present unique safety and operations issues. SMVs include vehicles that do not maintain a constant speed of 25 mph, such as large farm equipment, construction vehicles, or horse-drawn buggies. Though the number of crashes involving SMVs is relatively small, SMV crashes tend to be severe. Additionally, SMVs can be encountered regularly on non-Interstate/non-expressway public roadways, but motorists may not be accustomed to these vehicles. This project was designed to improve transportation safety for SMVs on Iowa’s public roadway system. This report includes a literature review that shows various SMV statistics and laws across the United States, a crash study based on three years of Iowa SMV crash data, and recommendations from the SMV community.

Revision to the SUDAS Traffic Signal Design Guide, TR-546, 2009

Changes in technology have an impact on standard practice, materials, and equipment. The traffic signal industry is constantly producing more energy-efficient and durable equipment, better communications, and more sophisticated detection and monitoring capabilities. Accordingly, this project provides an update to the traffic signal content within the Statewide Urban Design and Specifications (SUDAS) Design Manual and Standard Specifications. This work was completed through a technical advisory committee with a variety of participants representing contractors, the Iowa Department of Transportation, cities, consultants, vendors, and university research and support staff.

Safety Benefits of Paved Shoulders, 2009

Single vehicle run-off-road (ROR) crashes are the largest type of fatal passenger vehicle crash in the United States (NCHRP 500 2003). In Iowa, ROR crashes accounted for 36% of rural crashes and 9% of total crashes in 2006. Run-off-road crashes accounted for more than 61.8% of rural fatal crashes and 32.6% of total fatal crashes in Iowa in 2006. Paved shoulders are a potential countermeasure for ROR crashes. Several studies are available which have generally indicated that paved shoulders are effective in reducing crashes. However, the number of studies that quantify the benefits are limited. The research described in this report evaluates the effectiveness of paved shoulders. Model results indicated that covariate for speed limit was not significant at the 0.05 confidence level and was removed from the model. All other variables which resulted in the final model were significant at the 0.05 confidence level. The final model indicated that season of the year was significant in indicating expected number of total monthly crashes with a higher number of crashes occurring in the winter and fall than for spring and summer. The model also indicated that presence of rumble strips, paved shoulder width, unpaved shoulder width, and presence of a divided median were correlated with a decrease in crashes. The model also indicated that roadway sections with paved shoulders had fewer crashes in the after period as compared to both the before period and control sections. The actual impact of paved shoulders depends on several other covariates as indicated in the final model such as installation year and width of paved shoulders. However, comparing the expected number of total crashes before and after installation of paved shoulders for several scenarios indicated around a 4.6% reduction in the expected number of monthly crashes in the after period.

Road Safety Audit for Union County IA 25 from the WCL of Creston to North H-24 Intersection, 2008

In April 2008 a preliminary investigation of fatal and major injury crashes on Iowa’s primary road system from 2001 through 2007 was conducted by the Iowa Department of Transportation, Office of Traffic and Safety. A mapping of these data revealed an apparent concentration of these serious crashes on a section of Iowa 25 north of Creston. Based on this information, a road safety audit of this roadway section was requested by the Office of Traffic and Safety. Iowa 25 is a two-lane asphaltic concrete pavement roadway, 22 ft in width with approximately 6 ft wide granular shoulders. Originally constructed in 1939, the roadway was last rehabilitated in 1996 with a 4-in. asphalt overlay. Except for shoulder paving through a curve area, no additional work beyond routine maintenance has been accomplished in the section. The 2004 traffic map indicates that IA 25 has a traffic volume of approximately 2070 vehicles per day with 160 commercial vehicles. The posted speed is 55 mph. This report contains a discussion of audit team findings, crash and roadway data, and recommendations for possible mitigation of safety concerns for this roadway section.

Feasibility of Visualization and Simulation Applications to Improve Work Zone Safety and Mobility

Visualization is a relatively recent tool available to engineers for enhancing transportation project design through improved communication, decision making, and stakeholder feedback. Current visualization techniques include image composites, video composites, 2D drawings, drive-through or fly-through animations, 3D rendering models, virtual reality, and 4D CAD. These methods are used mainly to communicate within the design and construction team and between the team and external stakeholders. Use of visualization improves understanding of design intent and project concepts and facilitates effective decision making. However, visualization tools are typically used for presentation only in large-scale urban projects. Visualization is not widely accepted due to a lack of demonstrated engineering benefits for typical agency projects, such as small- and medium-sized projects, rural projects, and projects where external stakeholder communication is not a major issue. Furthermore, there is a perceived high cost of investment of both financial and human capital in adopting visualization tools. The most advanced visualization technique of virtual reality has only been used in academic research settings, and 4D CAD has been used on a very limited basis for highly complicated specialty projects. However, there are a number of less intensive visualization methods available which may provide some benefit to many agency projects. In this paper, we present the results of a feasibility study examining the use of visualization and simulation applications for improving highway planning, design, construction, and safety and mobility.

Evaluating the Relationship between the Driver and Roadway to Address Rural Intersection Safety using the SHRP 2 Naturalistic Driving Study Data, RB05-013, 2016

Rural intersections account for 30% of crashes in rural areas and 6% of all fatal crashes, representing a significant but poorly understood safety problem. Transportation agencies have traditionally implemented countermeasures to address rural intersection crashes but frequently do not understand the dynamic interaction between the driver and roadway and the driver factors leading to these types of crashes. The Second Strategic Highway Research Program (SHRP 2) conducted a large-scale naturalistic driving study (NDS) using instrumented vehicles. The study has provided a significant amount of on-road driving data for a range of drivers. The present study utilizes the SHRP 2 NDS data as well as SHRP 2 Roadway Information Database (RID) data to observe driver behavior at rural intersections first hand using video, vehicle kinematics, and roadway data to determine how roadway, driver, environmental, and vehicle factors interact to affect driver safety at rural intersections. A model of driver braking behavior was developed using a dataset of vehicle activity traces for several rural stop-controlled intersections. The model was developed using the point at which a driver reacts to the upcoming intersection by initiating braking as its dependent variable, with the driver’s age, type and direction of turning movement, and countermeasure presence as independent variables. Countermeasures such as on-pavement signing and overhead flashing beacons were found to increase the braking point distance, a finding that provides insight into the countermeasures’ effect on safety at rural intersections. The results of this model can lead to better roadway design, more informed selection of traffic control and countermeasures, and targeted information that can inform policy decisions. Additionally, a model of gap acceptance was attempted but was ultimately not developed due to the small size of the dataset. However, a protocol for data reduction for a gap acceptance model was determined. This protocol can be utilized in future studies to develop a gap acceptance model that would provide additional insight into the roadway, vehicle, environmental, and driver factors that play a role in whether a driver accepts or rejects a gap.

Maintenance of Traffic for Innovative Geometric Design Work Zones, 2015

Currently there are no guidelines within the Manual on Uniform Traffic Control Devices (MUTCD) on construction phasing and maintenance of traffic (MOT) for retrofit construction and maintenance projects involving innovative geometric designs. The research presented in this report addressed this gap in existing knowledge by investigating the state of the practice of construction phasing and MOT for several types of innovative geometric designs including the roundabout, single point urban interchange (SPUI), diverging diamond interchange (DDI), restricted-crossing left turn (RCUT), median U-turn (MUT), and displaced left turn (DLT). This report provides guidelines for transportation practitioners in developing construction phasing and MOT plans for innovative geometric designs. This report includes MOT Phasing Diagrams to assist in the development of MOT strategies for innovative designs. The MOT Phasing Diagrams were developed through a review of literature, survey, interviews with practitioners, and review of plans from innovative geometric design projects. These diagrams are provided as a tool to assist in improving work zone safety and mobility through construction of projects with innovative geometric designs. The aforementioned synthesis of existing knowledge documented existing practices for these types of designs.

Review of Geometric Design Criteria and Lighting Design Criteria, 1968

The investigations for this report were initiated in October, 1967, to perform the following: l. Review the current Iowa State Highway Commission roadway geometric design standards and criteria for conformance with national policies and recent research findings with special attention to high way safety. 2. Review the current Iowa State Highway Commission roadway lighting design standards and criteria for conformance with national policies and recent research findings with special attention to high way safety

Safety Edge Crash Modification Factors, Tech Brief, 2016

This study evaluated the safety impact of the Safety Edge for construction projects in 2010 and 2011 in Iowa to assess the effectiveness of the treatment in reducing crashes.