Influence of Infrastructure Design on Distracted Driving (2022)

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

2 Chapter 1. Introduction 1.1 Background The topic of driver distraction has attracted considerable attention in recent years. About 9% of fatal crashes are reported as distraction-affected crashes (National Center for Statistics and Analysis 2019). Distraction is any activity that diverts a driver’s attention from the driving task, including cell phone use; eating, drinking, or smoking; adjusting vehicle controls; reaching for or moving objects; attention to passengers; personal grooming; inattention; and attention to features outside the vehicle (NHTSA, 2021). Much of the public discussion has focused on texting and the use of cell phones. Although the majority of distractions are driver behaviors (e.g., texting, eating, personal grooming) or related to situations within the vehicle (e.g., interacting with passengers, adjusting vehicle controls), some distractions occur outside the vehicle. The latter are referred to in this report as outside-the-vehicle distractions (OVDs). Stutts et al. (2001) evaluated distraction-related crashes recorded in the National Highway Traffic Safety Administration (NHTSA) Crashworthiness Data System, which includes an annual sample of approximately 5,000 police-reported crashes involving at least one vehicle being towed from the scene. The authors found that around 8.3% of drivers involved in crashes were reported as being distracted and estimated that almost 30% of the crashes in which those drivers were involved were attributed to scenarios outside the vehicle (whether involving a person, object, or event). Glaze and Ellis (2003) evaluated a survey completed by law enforcement officers that described crashes in Virginia involving one or more drivers who were noted as being inattentive. The authors reported that 13% of the crashes described in the survey involved drivers who were distracted by something outside of the vehicle and 10% involved drivers looking at scenery or landmarks. Roadway infrastructure also contributes to crash risk, although typically in the form of deficient elements (e.g., poor pavement friction, narrow shoulders, difficult geometry) (Treat et al. 1979). However, some infrastructure elements may cause driver distraction to such a degree that they pose a risk. Because long glances away from the driving task are correlated with crash risk (Klauer et al. 2006, Olson et al. 2009, Klauer et al. 2010, Victor et al. 2015), infrastructure features that cause drivers to fixate on that feature are the most likely to be problematic. For instance, drivers may fixate on objects that are unusual (e.g., aesthetic bridges) or confusing (e.g., signing or markings) or that require an unusual amount of time to locate (e.g., a specific wayfinding sign among multiple roadside objects). While many studies have focused on driver distractions such as cell phone use, the impact of infrastructure elements on distraction and the extent to which they may cause distraction has not been well studied. 1.2 Objectives With the exception of billboards and general urban clutter, very few IRDs have been researched in the past. As a result, the interaction between the built environment and driver distraction is not

3 well understood. This project provides an opportunity to develop a better understanding of this interaction. To broaden the understanding of the relationships between roadway or roadside features and IRD crashes, the objectives of BTS-09 are as follows: • Develop a set of conceptual Safety Frameworks to evaluate the association between distracted driving and roadway or roadside infrastructure. • Assess the efficacy of the Safety Frameworks. • Develop guidance for stakeholders interested in addressing IRD. 1.3 Overview of Report This report describes activities undertaken to meet the objectives of BTS-09 and provides the project’s conclusions and recommendations. The report is organized as follows: • Chapter 2 describes common measures of distraction as well as surrogate measures for distraction that may be useful for the various types of data that are available. • Chapter 3 provides a literature review, which includes a summary of studies that have identified the safety impacts of OVDs as well as studies that have assessed the safety impacts of specific infrastructure elements (e.g., billboards, railroad crossings). • Chapter 4 outlines the databases that were examined to assess their suitability for use in evaluating the impact of IRDs in general as well as their feasibility for use in developing the Safety Frameworks for this study. • Chapter 5 summarizes the general outline for the Safety Frameworks developed in this study, which includes the following: o Overview of the type of analysis conducted. o Research questions evaluated. o Data sets utilized. o Description of the analysis conducted, including variables used, statistical methods, and results. o Discussion on the efficacy of the approach. • Chapter 6 outlines a Safety Framework for the use of crash narratives to assess the impact of infrastructure design on distraction. The framework utilized crash narratives from the state of Michigan. Crash narratives for fatal and serious injury crashes that had been coded as involving an OVD were reviewed and the data were analyzed; the resulting analysis provides a template that could be used to conduct a similar analysis. • Chapter 7 outlines a Safety Framework for the use of crash data to assess the impact of infrastructure design on distraction. Crash data from the state of Iowa, along with a wind turbine database, were used to develop several different models that could be used as templates to evaluate the efficacy of using crash data to develop relationships between infrastructure elements and distraction. • Chapter 8 outlines the first of two Safety Frameworks for the use of naturalistic driving study (NDS) data to assess the impact of infrastructure design on distraction. This framework used a curated data set from the Second Strategic Highway Research Program (SHRP2) NDS to evaluate driver behavior in the vicinity of railroad crossings. The framework demonstrates an

4 approach for using SHRP2 NDS data to assess the impact of infrastructure elements on distraction. • Chapter 9 outlines the second of two Safety Frameworks for the use of NDS data to assess the impact of infrastructure design on distraction. This framework used a curated data set from the SHRP2 NDS to evaluate the impact of overhead dynamic message signs (DMS) on distraction and demonstrated another approach for using the SHRP2 NDS data. • Chapter 10 outlines a Safety Framework for the use of driving simulator data to assess the impact of infrastructure design on distraction. The study used a curated data set from the University of Iowa’s National Advanced Driving Simulator (NADS) to evaluate driver behavior in the vicinity of highway signs. The framework demonstrates an approach for using driving simulator data to assess the impact of infrastructure elements on distraction. • Chapter 11 summarizes the findings of this study, makes recommendations, and provides a list of research questions worth exploring in the future. 1.4 Common Definitions Working definitions of the terms utilized in this research were developed to ensure consistency throughout the project. The key terms are defined below. 1.4.1 Infrastructure An operational definition of what constitutes an infrastructure element was developed based on existing definitions of infrastructure and in consideration of the project’s objectives. The working definition of infrastructure varies considerably among stakeholders. Transportation agencies generally tend to think of infrastructure in terms of their own assets and facilities. Examples include pavements, bridges, tunnels, traffic signals, signs, pavement markings, roadway lighting, culverts, and bicycle or pedestrian facilities. From this perspective, infrastructure ends abruptly at the right-of-way line and almost certainly excludes anything built on adjoining privately owned land. The Victorian Roadway Management Act (Australia) defines infrastructure as follows: “the infrastructure which forms part of a roadway, pathway, or shoulder, including structures forming part of the roadway, pathway or shoulder; materials from which a roadway, pathway, or shoulder is made” (Zelada and Eddy 2019). The U.S. Bureau of Transportation Statistics defines infrastructure as follows: “Transportation infrastructure consists of the structures that support the movement of goods and people, such as highways and streets, bridges, railroads, airports, and ports. It does not include transportation equipment like motor vehicles, aircraft, and ships” (BTS 2020). The International Energy Agency defines roadway infrastructure as follows: “Road transport infrastructure is defined as the road network and associated physical infrastructure, such as signage, lighting, and vehicle refueling services (i.e., gas stations)” (IEA 2011). All definitions agree that roadway infrastructure encompasses the roadway, shoulder, and any roadway-related items. Other stakeholders may define infrastructure more broadly to include any human-created device or structure that is readily visible to motorists. Examples could include

5 signs, billboards, buildings, sculptures, monuments, outdoor lighting systems, wind turbines, and similar structures or items that are typically situated adjacent to the roadway (i.e., within or outside of the clear zone but still visible to drivers), including items that are neither within the right-of-way nor part of the roadway infrastructure. Since this definition creates an impossibly large number of variables to consider, the definition may be refined to include those objects whose purpose is related to the transportation infrastructure, those for which a roadway agency is responsible, or those whose placement a roadway agency is likely to be able to address through policy (e.g., billboards, sculptures, monuments, wind turbines). As a result, the operating definition of infrastructure for this project is as follows: Infrastructure is defined as any fixed object that forms part of the roadway cross section, including the roadway itself, the shoulder, the median, and any right-of-way owned or operated by the corresponding roadway agency. Additionally, other fixed objects may be considered infrastructure if they are located adjacent to the roadway and their primary function is related to the traveling public (e.g., billboards) or a transportation agency is reasonably likely to be able to implement a policy addressing their use or placement (e.g., monuments or wind turbines). This definition includes physical assets as well as design elements and the location of those design elements. Design elements include, but are not limited to, horizontal and vertical curvature, roadway cross sections, roadside features, bridges and structures, intersections, access points, drainage elements, railroad crossings, signing, and lighting. 1.4.2 Rural and Urban The 2010 United States census defined “urban” based on the population density within individual census tracts and “rural” as anything not considered to be urban. The most basic definition of “urban” includes two types of areas: an “urbanized area,” which is a contiguous group of census tracts with a population of 50,000 or more, and an “urban cluster,” which is a contiguous group of census tracts of between 2,500 and 50,000 people (U.S. Census Bureau 2011). For the sake of simplicity, “rural” may be defined as anything outside of an incorporated area of 2,500 or more people. However, census tracts do not necessarily correspond to municipal boundaries. Additionally, due to the irregular shape of the census’s urban boundaries, they are not readily usable by law enforcement officers. As a result, the urban or rural flags on crash report forms generally do not coincide with the census’s urban and rural areas. For this reason, it was decided that when crash data were used, the attending officer’s description would designate rural versus urban unless spatial position or other information in the crash record suggested that a different designation should be used. For the purposes of BTS-09, the definition of rural versus urban is as follows: When an event can be spatially located, “rural” is defined as “anything outside of an incorporated area of 2,500 or more people.” Alternatively, “urban” is defined as “anything within an incorporated area of 2,500 or more people.” When only a crash form definition is available to distinguish rural from urban, the attending officer’s designation of rural versus urban will be utilized.

6 1.5 Summary This chapter described the background and objectives of this study, an overview of the report, and the working definitions that are used throughout the report. In the upcoming chapters, we will present background information on driver distraction and review the current state of knowledge related to IRD.