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Pedestrian and Bicyclist Traffic Control Device Evaluation Methods

CHAPTER 1. INTRODUCTION

OVERVIEW

State, county, and city transportation agencies implement a variety of innovative countermeasures to improve pedestrian and bicyclist safety (see figure 1). These countermeasures include the following:

• Traffic control devices.
  
  
• Geometric designs.
  
  
• Educational programs.
  
  
• Enforcement activities.

© Texas Transportation Institute

Figure 1. Photo. Bar pair crosswalk intended to improve pedestrian and bicyclist safety.

When determining whether these countermeasures are effective, most engineers and planners rely on anecdotal observations or their professional judgment. In some cases, a limited quantitative safety evaluation is conducted. However, these evaluations are often limited in terms of scope, experimental design, and/or statistical rigor because many State and local agencies lack research funds or sufficient knowledge of experimental design and statistics to conduct proper evaluations of new traffic control devices or other traffic features.

If better safety evaluation methods for pedestrian and bicyclist countermeasures were available to State and local agencies, local evaluations could provide sound safety effectiveness data for decision making on national standards like MUTCD or American Association of State Highway and Transportation Officials (AASHTO) guides and programs.

One problem with evaluating bicyclist and pedestrian safety treatments is the difficulty of using direct safety outcomes such as pedestrian and bicyclist crashes. These types of crashes are relatively infrequent and therefore occur in small quantities. Consequently, any pedestrian or bicyclist safety evaluation that uses a crash-based analysis would require tens or hundreds, if not thousands, of study sites to obtain statistical significance. This is often impractical or impossible in typical experiments involving innovative devices. Additionally, local agencies rarely have the resources necessary to install and evaluate innovative traffic control devices at more than a few locations. As a result, surrogate MOEs are often the only feasible approach to evaluate the effectiveness of a device. A significant focus of this report is to provide an approach for establishing when a particular surrogate measure is appropriate.

OBJECTIVE

The purpose of this report is to assist practitioners in conducting sound evaluations on the effectiveness of pedestrian and bicyclist traffic control devices. The report is designed for practitioners (State transportation departments, county or city engineers, and other traffic officials). Additionally, personnel without specialized statistical analysis skills should be
able to use the report.

The report includes (but is not limited to) the following information:

• When to conduct an evaluation.
  
  
• Why evaluations are important and who will use them.
  
  
• What practitioners should know before requesting permission to conduct an evaluation of an innovative traffic control device.
  
  
• When and how to write a request for experimentation.
  
  
• Examples of evaluation reports.
  
  
• MOEs (including crash-based measures, user understanding, compliance and behavior, and other surrogate measures).
  
  
• Evaluation design (before-after with/without comparison sites, cross sectional, etc.).
  
  
• Data collection (exposure, behavior, compliance, traffic data, crashes, etc.).
  
  
• Common statistical analysis techniques to determine the likelihood that the measured results are a true reflection of the device’s effectiveness rather than based on chance.
  
  
• Common evaluation errors, such as regression to the mean, and how to avoid them.

This report provides basic information on each of these elements so that a sound evaluation can be conducted. A reliable evaluation, regardless of whether the results are positive or negative, will allow other practitioners to learn from and build on the experience of the implementation of a new traffic control device, placement, or application. Sound evaluations can also lead to the dismissal or elimination of a traffic control device either because it does not provide positive driver or pedestrian results or because it does not offer an improvement over existing traffic control options. One such example is the use of fluorescent yellow-green crosswalk markings. Evaluation of these markings showed that they offered no advantage over standard white crosswalk markings. Therefore, they were not adopted for further use.

FHWA and the National Committee on Uniform Traffic Control Devices (NCUTCD) rely on evaluations to determine if a new device or treatment should be adopted in MUTCD or if it should be considered for further evaluation. Although an evaluation conducted by one agency may not be sufficient to determine if a device should be adopted, the results may be combined with other evaluations completed by other agencies. Inadequate, incomplete, or improper evaluations will lead to poor decision making by agencies and other practitioners.

KEY COMPONENTS

Key components or documents include the following:

• The 2009 MUTCD is the legal standard that must be used by road managers nationwide in order to install and maintain traffic control devices on all public streets, highways, bikeways, and private roads open to public traffic (see figure 2).⁽¹⁾
  
  

© Texas Transportation Institute

Figure 2. Photo. The 2009 MUTCD.

•  NCUTCD is an organization whose purpose is to assist with the development of standards, guidelines, and warrants for traffic control devices and practices used to regulate, warn, and guide traffic on streets and highways. NCUTCD makes recommendations to FHWA and other agencies for revisions to MUTCD and other national standards. NCUTCD develops public and professional awareness of the principles of safe traffic control devices and practices and provides a forum for qualified individuals with diverse backgrounds and viewpoints to exchange information.⁽²⁾
  
  
• FHWA specializes in highway transportation and performs research in many areas including transportation operations, highway materials, construction methods, and safety.

The FHWA MUTCD team administers MUTCD, including the experimentation process, and is available to assist with technical questions or comments about MUTCD. Contact information for the team is available at http://mutcd.fhwa.dot.gov/team.htm.