TECHBRIEF |
Driver Attitudes and Behaviors at Intersections and Potential Effectiveness of Engineering CountermeasuresPublication No. FHWA-HRT-05-158 FHWA Contact: Ray Krammes, HRDS-05, 202–493–3312 To view PDF files, you need the Acrobat® Reader®. This document is an executive summary of the report Driver Attitudes and Behaviors at Intersections and Potential Effectiveness of Engineering Countermeasures, FHWA-HRT-05-078, published by the Federal Highway Administration in November 2005. Introduction and Background This report describes the results of the focus group portion of this research. The objective of the focus groups was to identify driver attitudes and behaviors related to intersection safety and to assess the likely impacts of new or existing infrastructure-based technologies/countermeasures. Focus group discussions provide an established method to obtain this rich information. These types of discussions allow researchers to probe responses and introduce new ideas in a flexible manner that cannot be achieved with quantitative research. Also, focus groups provide continual feedback and exchange between the moderator and the respondents. The opportunity for self-correction gives more robust and accurate responses. For example, if an answer or response is unclear or ambiguous, the interviewer can rephrase the question and gather desired insights accordingly. If new ideas emerge during a focus group, the interviewer can investigate them in more depth. Because the samples are small and not representative of the total population, and thus minimally generalizable, qualitative research cannot be a valid substitute for quantitative research. Because the research relies on nondirective, semistructured interviews, the stimulus situation is not the same for every respondent. Therefore, focus group studies should not be viewed as definitive; quantitative research is also necessary to arrive at indepth conclusions. During the focus groups, participants discussed various intersection driving scenarios and associated countermeasures. The discussion scenarios were selected based on crash data and the availability of infrastructure-based countermeasures. In particular, an analysis of crash types at intersections using 1998 General Estimates System (GES) data conducted by Najm, Koopmann, and Smith indicates that the most common crash types involve straight crossing path crashes in signalized intersections (SCP/SI) and straight crossing path crashes in unsignalized intersections (SCP/UI), in addition to left turn across path/opposite direction (LTAP/OD) crashes at signalized intersections, and left turn across path/lateral direction (LTAP/LD) crashes at unsignalized intersections.(1) Three of these crash types were selected as scenarios, including SCP/SI, LTAP/OD (signalized intersection), and LTAP/LD (stop-controlled intersection), based on maximizing the diversity of situational factors and countermeasure types that could be presented to focus group participants. In addition to these crash types, a scenario based on rear-end crash situations was also added, because this type of crash at intersections was highly prevalent.
In particular, rear-end crashes at intersections comprise approximately 12 percent of all roadway crashes, according to 1993 GES data.(2) Four focus groups were conducted at each of three test sites: Washington, DC; Chicago, IL; and Seattle, WA. At each site, the four groups corresponded to the age/gender characteristics identified as important to this project (see table 1). The groups were:
At each site, the focus groups took place over two separate evenings, with two focus groups conducted per evening. A total of 119 individuals participated in the focus groups. Table 1. Number of focus group participants as a function of location and age/gender characteristics.
Materials for the focus group sessions included written and graphic descriptions of the intersection scenarios and corresponding countermeasures. The graphics in the main report show how the countermeasures look to drivers and include schematic layouts to coincide with each scenario to demonstrate how the countermeasures function and how they are positioned in the roadway environment. The graphics were accompanied by clear written explanations of how the countermeasures worked as well as any impacts they would have on the traffic flow. Key visual aspects (e.g., flashing lights) that may not be evident from the graphics were also explained to the focus group participants. Most countermeasures were selected for particular scenarios if they addressed one or more of the primary driver-related causal factors identified with each crash type.(2) If data were available, the potential effectiveness of individual countermeasures was also considered.(3) To reduce the chances of biasing the participants' evaluations of the relative potential effectiveness of individual countermeasures, the researchers tried to match the level of description and detail for all countermeasures, as well as present the information in a common format where possible. The four scenarios addressed in the focus groups and discussed below were:
The Moderator Guide in appendix B of the main report provides a step-by-step overview of the discussion flow for the scenarios. In general, the discussion focused on describing each scenario, gaining an understanding of driver behavior in the scenarios (i.e., asking how drivers behave in this situation), and understanding the many primary and secondary factors (e.g., situations, attitudes, habits, beliefs, and consequences) that influence their decisions and behaviors during the scenario (i.e., why drivers behave the way they do). Following the discussions of the scenarios, the researchers addressed the focus group participants' opinions of and responses to nine countermeasures:
The researchers developed a brief take-home survey (shown in appendix D of the main report) to obtain participant responses about relevant intersection activities that were not discussed in the focus groups due to time restrictions. The questionnaire included 12 Likert scale and open-ended questions. All questions addressed the following scenario: "These questions are about the driving situation discussed in the group where the light turns yellow just as you approach an intersection. Specifically, you have enough time to stop if you brake quickly; otherwise the light is likely to turn red while you are in the intersection unless you speed up quite a bit." Results and Conclusions The results and conclusions below are organized according to the four intersection scenarios that have been the focus of this investigation: (1) red-light running, (2) left turns at busy intersections, (3) turning left onto a major road with moderate traffic, and (4) rear-end crashes. For each of the four scenarios, we present our conclusions as answers to three key questions that reflect the technical objectives for the focus groups:
Scenario 1: Red-Light Running
What are drivers most likely to do in this scenario? For this scenario, the focus groups indicated that almost all older drivers would stop at the intersection, while many to most middle-aged and younger drivers would go through the intersection and violate the red light. Results from the take-home survey confirmed this general trend. Interestingly, the drivers who indicated that they would go through the light acknowledged that they would do so in a deliberate and purposeful manner based on the current circumstances. In other words, they recognized the risks associated with running a red light under the circumstances described above, yet would often choose to do so anyway. Figure 4 summarizes the responses from key questions included in the take-home survey.
1 All countermeasures are labeled using an "X.Y" designation, where "X" refers to the scenario and "Y" refers to the relevant countermeasure associated with that scenario. For example, "1.1" refers to the first countermeasure discussed within scenario 1, and "1.2" refers to the second countermeasure discussed within scenario 1. Why do drivers engage in these behaviors? The take-home surveys indicated that drivers' decisions to go through on a late yellow/early red light are primarily based on attitudes/beliefs and social norms. This encouraging preliminary finding means these factors can be addressed by typical public awareness and similar advertising campaigns. The factors that are more difficult to change, such as habits and experience with critical incidents, had no impact in driver decisionmaking. What engineering countermeasures have the most promise for improving traffic safety? Opinions about high-visibility traffic lights (countermeasure 1.2) were mixed: older drivers believe that they would improve safety, while younger drivers (males in particular) believe that they would not help or did not apply to them. Many drivers thought that this countermeasure would work best in suburban or rural areas because it might otherwise get lost in all of the other downtown lights and other traffic control devices. Opinions about the likelihood of advance traffic-light warning signs (countermeasure 1.3) improving safety were very mixed. Most subjects thought that this countermeasure would be most helpful in high-speed areas (i.e., rural and suburban locations). Opinions about intersection collision warning systems (countermeasure 1.4) were very positive; many drivers—across all age groups and locations—believe that this type of countermeasure would definitely aid drivers' ability to stop before entering a potentially dangerous intersection. Some respondents expressed concerns about drivers' knowledge of the system and questioned whether warning information would occur in time for drivers to stop safely. Many drivers expressed concern that this countermeasure was aimed at the law-abiding driver, not the red-light runner. However, most drivers preferred this approach to an in-vehicle only approach. Scenario 2: Left Turns at Busy Intersections
What are drivers most likely to do in this scenario? Why do drivers engage in these behaviors? What engineering countermeasures have the most promise for improving traffic safety? Scenario 3: Turning Left Onto a Major Road With Moderate Traffic
What are drivers most likely to do in this scenario? Why do drivers engage in these behaviors? What engineering countermeasures have the most promise for improving traffic safety? Opinions about synchronized adjacent traffic signals (countermeasure 3.2) were generally positive, with well over half of the drivers expressing the opinion that this countermeasure would improve safety. Scenario 4: Rear-End Crashes
What are drivers most likely to do in this scenario? Why do drivers engage in these behaviors? What engineering countermeasures have the most promise for improving traffic safety? Opinions about improved skid resistance (countermeasure 4.2) were positive. Most focus group participants believed they would improve safety and would be preferable to rumble strips. Many believed a combination of the rumble strips and the improved skid resistance countermeasure would be the most effective intervention. References
Researchers—This study was performed by C.M Richard, E.F. Michaels, and J.L. Campbell at Battelle Human Factors Transportation Center in Seattle, WA. Distribution—This TechBrief is published on the Turner-Fairbank Highway Research Center Web site only. To download this TechBrief, go to www.tfhrc.gov. Availability—The report, Driver Attitudes and Behaviors at Intersections and Potential Effectiveness of Engineering Countermeasures (FHWA-HRT-05-078), which is the subject of this TechBrief, is being published on the Turner-Fairbank Highway Research Center Web site only. To download this report, go to www.tfhrc.gov. Key Words—Driver attitudes and behaviors, focus groups, intersection safety, engineering countermeasures. Notice—This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document. The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers' names appear in this report only because they are considered essential to the objective of the document. Quality Assurance Statement—The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement. |
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March 2006 |
HRT–05–158 HRDS-05/03-06(WEB)E |
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