Nighttime Visibility of Traffic Signs: Chapter 3 - Summary of Findings

CHAPTER 3 - SUMMARY OF FINDINGS

There were essentially three major parts to the workshops. The first part of the workshop consisted of presenting information to the participants regarding background information, retroreflectivity principles, updates to the minimum retroreflectivity levels, and implementation options. The second part of the workshop was the nighttime sign visibility demonstration. The third part of the workshop was devoted to soliciting input from the participants regarding the FHWA effort to develop a proposed rule on minimum retroreflectivity levels. While participants were encouraged to ask questions and offer opinions at any time during the workshops, most of the discussion and input came during the second day of the workshop. The main findings of the workshops were identified during the second day of each workshop. This input was the primary reason for conducting the workshops and will provide the greatest value to the FHWA in future rulemaking efforts. A key focus of the second day's discussion was to try and find some level of consensus among each workshop's participants on some of the key issues.

The general format of the second day was similar for each workshop. Participants started by discussing the results of the nighttime demonstration. This was followed by a discussion of the key issues related to nighttime sign visibility, minimum sign retroreflectivity, and the scope of a minimum retroreflectivity rule. The workshop concluded with the participants developing recommended language for the MUTCD. For the second through fourth workshops, the key issues were discussed among all the participants with the objective of trying to identify the most significant issues that impact the development and implementation of minimum retroreflectivity and/or nighttime visibility guidelines. The discussion of key issues was conducted in a slightly different manner at the first workshop (Lakewood). At this workshop, the participants were divided into two groups for small group discussions on specific topics. The groups then switched topics so that each group discussed all of the topics. Afterward, the group discussion leaders presented a summary of each groups' opinions.

The workshops proved to be a valuable tool for identifying and addressing the comments and concerns of the participants. The workshops also provide valuable insight into issues that need to be considered in developing a proposed rule on minimum retroreflectivity levels. There were a number of consistent messages throughout all of the workshops and this chapter summarizes the key findings identified in the four workshops. In many cases, the statements and opinions of the participants were consistent from one workshop to another and represent the thoughts of most participants. In other cases, the findings described in this chapter may represent those of a few participants, but are strong opinions that merit mention in this report. Because the workshops were focused on agency concerns, it should also be noted that the opinions described in this chapter are mostly those of the public agency participants, not the private sector participants.

MAJOR FINDINGS

The initial portion of the discussion period on the second day was devoted to developing a list of issues and defining the most critical aspects of providing nighttime sign retroreflectivity and visibility. Each of the four workshops developed a list of issues that addressed topics ranging from the technical aspects of minimum retroreflectivity levels to policy implications of revising the MUTCD to address sign visibility and/or retroreflectivity. Most of the opinions identified during these discussions were shared by the majority of the public agency personnel participating in the workshops. The major findings, representing the opinions of the public agency personnel, are presented below. Unless indicated otherwise, virtually all of the public agency participants agreed with these findings.

• Participants recognized that governmental agencies have a responsibility to provide signs that have a reasonable level of daytime and nighttime visibility.
• Participants agreed that there are already general retroreflectivity and sign inspection requirements in the MUTCD that agencies should be following.
• The primary focus of having minimum levels of in-service retroreflectivity is to improve the nighttime visibility of signs. Drivers need signs that are visible, but not necessarily signs above a specific level of retroreflectivity. Therefore, the proposed rule should focus on nighttime sign visibility instead of minimum retroreflectivity.
  • Retroreflectivity is a sign property that is only one of several factors that defines the overall visibility of a sign. Examples of other factors that affect sign visibility include the amount of illumination reaching the sign; the positional relationship between the headlamps, sign, and driver; the luminance needs of the driver; and the transmissivity of the windshield.
  • A sign's retroreflectivity may be at the minimum level, but the sign may not be visible for any number of reasons (i.e., sight distance obstructions, inadequate illumination, or dew on the sign). Accordingly, the MUTCD focus should be on nighttime sign visibility, not just retroreflectivity. Addressing sign visibility instead of retroreflectivity provides greater flexibility in the implementation options rather than just addressing retroreflectivity.
• The workshop participants would like to see the FHWA develop information that provides a stronger link between improving nighttime sign visibility and reducing nighttime crashes. They felt that this type of safety data should be included as part of the rulemaking effort if agencies will be required to devote greater resources to improving nighttime sign visibility. The participants felt that public agency staff would be more effective in promoting sign improvement programs and requesting larger sign budgets if they had data that indicated that such programs and expenditures would lead to a substantial decrease in crashes.
• Many of the agencies participating in the workshop were critical of the 1993 Congressional mandate to revise the MUTCD to include a minimum standard of retroreflectivity. Some opposed the mandate because of the "unfunded mandate" aspects; others opposite the mandate because of the lack of proven safety benefits associated with the minimum levels. Because the mandate was implemented through a legislative process, some participants indicated that they may use the legislative process to try to rescind the mandate.
  • The participants did not want the MUTCD to be revised in a manner that would require their agencies to devote greater resources to signing activities or increase their tort exposure. Participant suggestions for minimizing the resource or tort impacts include:
  • The MUTCD should establish a general objective or goal and allow agencies the flexibility to develop policies and procedures to implement the objective or goal. The MUTCD should not require specific actions of agencies other than what an agency determines is needed to meet the goal. The agencies should be responsible for developing the specific procedures to be followed to meet the goal.
  • The MUTCD language should be formatted as guidelines (should) and not as a standard (shall).
  • The MUTCD guidelines should be simple to implement and the equipment and procedures required to implement the guidelines should be reasonably available to agencies.
  • The MUTCD should describe options for minimum visibility or retroreflectivity that agencies can choose from according to the resources and objectives of individual agencies.
  • The MUTCD should not contain numeric values for minimum levels of retroreflectivity. It is preferable that specific numeric values be provided in a supplemental document.
  • The MUTCD guidelines should be usable by government agencies that do not have a transportation department or engineering staff.
  • Participants felt that agencies should have the option of exempting some signs from the visibility/retroreflectivity guidelines. Examples include parking, pedestrian, and bicycle signs. Other types of signs were also mentioned as possible exemptions.
• The MUTCD language should provide agencies with some degree of flexibility on the time frame to replace signs found to be inadequate. Examples of phrases that would provide this type of flexibility include:
  • Replace as soon as reasonable.
  • Replace as soon as conditions and resources permit.
  • Schedule for replacement when a need is identified.
• The participants indicated that transportation agencies (especially the local ones) have limited ability to devote additional resources to signing activities without reducing the resources devoted to other important and essential transportation-related programs (such as pavement repair, signal timing, and maintenance of signs and markings). The participants felt that federal funding should be provided to both state and local agencies to encourage agencies to embrace the concept of improved nighttime sign visibility.
• The time frame for implementing the MUTCD guidelines should be based upon the expected retroreflective life of signs. This may be a function of material warranties, documented service life, or a time frame consistent with asset management policies. The agencies also expressed the need for a three-year period to get improved sign management processes in place.
• The attorneys participating in the workshops recommended using the term "reasonable" to describe the visibility or retroreflectivity performance threshold. They recommended avoiding terms and phrases such as "ensure (or assure) adequate (or effective) sign visibility."

EVALUATION METHODS

A significant portion of the workshops was devoted to discussions on the options that might be available to agencies to improve the nighttime visibility of signs. Several different terms were used to describe the options, including evaluation methods, assessment procedures, implementation options, and management processes. All of the terms are intended to describe actions that an agency can take to provide a reasonable level of nighttime sign visibility to road users. The term "evaluation methods" is used in this report to represent the various actions that an agency may use to provide a reasonable level of nighttime sign visibility.

There was essentially unanimous agreement among the public sector participants that the MUTCD should not dictate the methods or processes to be used to determine that signs meet the goal of reasonable nighttime visibility. Instead, the MUTCD should describe various evaluation methods that agencies can choose from to provide reasonable nighttime sign visibility. The ability to choose from several options will allow agencies to adopt a method that best fits the resources and current practices of the individual agency.

A number of different methods were presented and discussed during the various workshops. Most can be divided into either of two categories - evaluation procedures and management processes. Evaluation procedures involve some type of assessment of the performance of individual signs and include actions such as visual inspection or retroreflectivity measurement. Management procedures represent processes that do not require an assessment of individual signs and is typically based on an expectation of expected retroreflective life. The following describes the methods that were identified by workshop participants as the most likely to be used by agencies.

• Visual Inspection - Signs are visually inspected during nighttime conditions to determine if the signs have a reasonable level of retroreflectivity. An agency may use several different methods of tying the visual inspection results to the minimum retroreflectivity levels. These methods may include formal training of the personnel conducting the inspections; standardization of the vehicle types, headlamps, and inspector age; and viewing calibration panels at or near minimum retroreflectivity values before conducting the inspection.
• Scheduled Replacement - Signs are scheduled for replacement before they reach the end of their expected retroreflective life. The expected service life is based on the time that a sign would last in the field before reaching the minimum level of in-service retroreflectivity. The expected sign life may be based on the warranty provided by the manufacturer or agency data on the service life of various sign sheeting materials. Prior experience has demonstrated that sign life varies according to many different factors, such as grade of sheeting; sheeting manufacturer; type of sign substrate; direction of exposure; climate; atmospheric contaminants; height and lateral distance from the edge of the travel lane; and other factors.
• Control Signs- Replacement of signs in the field is based on the performance of a sample of control signs. The control signs may be a small sample located in a maintenance yard or a larger sample of signs in the field. The control signs are closely monitored by the agency to determine the end of service life for signs in the field. Various methods can be used to determine the end of service life for the control signs, including measured retroreflectivity, comparison to inspection panels, or visual inspection. When a control sign reaches the end of its life, all associated signs in the field are also replaced.
• Inspection Panels - Small panels at specific retroreflectivity levels are used as part of a visual inspection to evaluate retroreflectivity. Panels are fabricated at retroreflectivity levels near the various minimum levels or an agency's replacement criteria. The panels are temporarily attached to a sign and then viewed from a distance. If the inspection panel is brighter than the sign, the sign should be replaced.
• Measured Retroreflectivity - The retroreflectivity of a sign is measured with a retroreflectometer instrument and compared to the minimum levels. If the measured retroreflectivity is less than the minimum, the sign should be replaced.
• Other Methods- Participants indicated that agencies should have the ability to identify additional methods that can be used to provide reasonable levels of nighttime sign retroreflectivity as they gain experience with these and other methods.
• Combination of Methods - Participants also indicated that an agency should be able to use some combination of these or other methods.

The following describe the general opinions and findings of the workshops relative to most of the evaluation and management methods described above.

• Visual Inspection
  • Visual inspections were perceived as the best option overall as well as the option most agencies are likely to adopt. They are also perceived to be the most likely means to find visibility problems with signs.
  • This method was also perceived to have the smallest administrative and fiscal burden of all the methods.
  • Many agencies already perform some type of periodic sign inspections, although not all inspections are performed at night.
  • Sign inspections are an important activity and are already recommended in the MUTCD in Section 2A.23 for both day and night conditions.
  • Inspections require a minimal investment of resources on the part of the agency beyond the current MUTCD requirements.
  • Visual inspections are subjective and more difficult to tie to minimum retroreflectivity levels.
  • Agencies will need to establish procedures to provide consistency within the agency as well as consistency in the implementation of the minimum retroreflectivity levels.
  • There may be a need to provide employee training programs so that agencies can conduct inspections. Inspection guidelines should address:
    • Type of vehicle used for inspections.
    • Type of headlamps in the inspection vehicle.
    • Aiming of inspection vehicle headlamps.
    • Age and visual acuity of the inspector(s).
    • Type of personnel that can conduct inspections. Some felt that non-transportation personnel from an agency (for example, secretaries or bookkeepers) should conduct the inspections as representative drivers. A few of the local agency participants wanted to use personnel from other governmental agencies to conduct the inspections as part of their regular duties (for example, police officers and other emergency personnel who routinely drive roads at night)
• Scheduled Replacement
  • Sign life could initially be based on warranty periods. More detailed information should be developed by agencies to refine the expected life of sign sheeting, as there is no relationship between warranty periods and minimum retroreflectivity levels.
  • This method requires agencies to know the type of sheeting for each sign.
  • Agencies would need to track sign age to determine replacement. Multiple options exist for tracking sign age.
    • An identification sticker can be placed on the front or back of the sign indicating the year of fabrication or installation. One agency currently places a two-digit number representing the year of fabrication on at the bottom of the face of the sign. Several agencies use colored stickers on the back of a sign to identify the year that a sign is fabricated or installed.
    • A sign management system can be used to track fabrication and installation dates of specific signs.
  • Computerized sign management systems provide an effective means of tracking the age of signs in an agency.
  • To improve the productivity of crews replacing signs, an agency may want to replace all signs throughout specific corridors at periodic intervals as an alternative to replacing individual signs located throughout an entire jurisdiction.
• Control Signs
  • This method requires agencies to have the capability to measure the retroreflectivity of the control signs.
  • Without an appropriate sampling process, the control signs may not be representative of the larger sign population they are intended to represent. This could lead to the replacement of signs that don't need replacing or not replacing signs that do need replacement.
    • Agencies will need guidelines on the number of control signs that are needed to appropriately represent signs in the field.
• Inspection Panels
  • Inspection panels are needed for each color and type of retroreflective sheeting.
  • This method is time consuming because it requires the attachment and removal of panel(s) for each sign inspected. It may be more cost effective to replace a sign in question rather than use the inspection panel to assess a marginal sign.
  • This method would most likely supplement one of the other methods as a means of evaluating signs when there is a question regarding replacement.
  • There are no current sources where agencies can obtain inspection panels at or near the minimum levels of sign retroreflectivity.
• Measured Retroreflectivity
  • This method provides the most direct means of implementing the minimum levels of in-service retroreflectivity developed by the research effort.
  • This method is time consuming if all the signs in a jurisdiction are measured. It may be best used to support one of the other methods or as a means of evaluating questionable signs.
  • Agencies need access to field retroreflectometers to use this method and personnel trained on the use of the retroreflectometers.
  • The level of precision associated with field measurement of sign retroreflectivity has not been established. While small differences between measured values and minimum levels are not likely to be significant from a performance standpoint, they could be significant from a tort standpoint.

Participants in some of the workshops indicated that a sign management system could also be used as one of the evaluation methods. However, a sign management system is a tool that would support one or more of the evaluation methods. A sign management system does not provide a means for evaluating nighttime sign visibility, but does provide a means of managing information that can be used to predict when a sign should be replaced without using field evaluation methods. Several participants mentioned that insurance carriers for some agencies will reduce the premiums if an agency uses a sign management system.

CURRENT PRACTICES

Participants in several workshops described some of the sign maintenance and replacement practices that their agencies are currently using or considering adopting. The following list describes some of the practices that were identified by different agencies. It should be noted that the facilitators did not attempt to make an accurate count of the practices used by the agencies participating in the workshops. Participant comments indicated that many of these practices have been implemented in the last few years. This suggests that some agencies have recognized the importance of implementing improved sign management processes.

• Sign inventory systems - At least five of the agencies represented at the workshops currently utilize some form of sign inventory system. At least one of these systems provides sign crews in the field with the capability to update the inventory system through the use of handheld Personal Data Assistants (PDAs). Several of the sign inventory systems are linked to Geographic Information Systems (GIS) data. Not many of the agencies currently maintain retroreflectivity data in their inventory systems; however, the systems that don't could be modified to include such data. Three additional agencies are currently implementing or considering the implementation of sign inventory systems.
• Visual inspections - Several agencies indicated that they conduct nighttime visual inspections on a regular basis. At least one of the agencies had conducted specific training for personnel involved in nighttime sign inspections.
• Sign improvement programs - Several of the state agencies mentioned that they have implemented programs to improve the quality of signing on a statewide basis.
  • Two states have initiated statewide sign replacement programs.
  • Two states have sponsored research to measure retroreflectivity of signs in the field. This data is being used to predict expected sign life.
• Sign age practices - At least two states described practices for indicating sign installation or fabrication dates in a manner that can be viewed by personnel traveling at normal roadway speeds.

IMPACTS

Throughout the workshop discussions, the public agency participants identified numerous perceived impacts that new requirements for improved nighttime visibility or minimum retroreflectivity would have on agencies. Many of the impacts are related to the additional resources that would be needed for an agency to implement any new criteria in the MUTCD. Other impacts are associated with other aspects of the concept.

• Administrative Impacts
  • New guidelines may require agencies to devote more personnel to signing activities. These personnel may need training to conduct the expanded duties.
  • Training activities may need to be coordinated at a national or state level. The training program may need to include some form of certification to identify those that are qualified to conduct sign evaluations.
  • Many agencies will need to increase their sign documentation efforts to have records that show evaluations were conducted and that signs met the evaluation criteria. Agencies will also need to keep these records over a longer period of time than they currently do.
• Fiscal Impacts
  • The magnitude of the fiscal impacts has not yet been sufficiently defined for the updated minimum retroreflectivity levels. Prior research has indicated that the impacts of the 1998 minimum values would be small for most agencies (11). The report stated that many agencies "will not likely feel any additional impact of implementing the minimum retroreflectivity guidelines."
  • The guidelines may lead to a higher sign replacement rate than presently exists. This will increase the signing costs for an agency.
  • Even if sign replacement rates remain the same, the use of more expensive sheeting may increase sign costs.
  • Factors that are expected to increase the fiscal burden on agencies are listed below. Not all impacts will apply to all agencies.
    • Cost of training personnel.
    • Cost of overtime pay for nighttime inspections.
    • Cost of acquiring evaluation equipment (for example, retroreflectometers or inspection panels).
    • Cost of additional documentation and longer retention of the information.
  • Unless the federal government provides supplemental funding, the fiscal resources required to meet the minimum visibility/retroreflectivity guidelines may have to be diverted from other transportation responsibilities.
  • It will be difficult for transportation management to support requests to elected officials for additional funding unless a documented safety benefit can be linked to the expenditures.
  • Implementing processes to manage sign replacement has been shown in some agencies to reduce overall sign costs, although the start-up costs can be large.
• Implementation Impacts
  • Some participants felt that conducting nighttime visual inspections were beyond the capabilities of their agency, primarily due to the overtime pay that would be required or the lack of training. A few participants noted that daytime sign inspections would be just as effective a nighttime visibility assessment tool as nighttime inspections. However, most participants agreed that daytime inspections cannot be used to reliably assess nighttime sign visibility.
  • Guidelines that eliminate the use of Type III (high intensity) sheeting for the legend of overhead signs will be a burden to many of the agencies with overhead signs. Most of these signs currently use Type III sheeting and the replacement intervals for these signs are typically longer than post-mounted signs.
  • Implementing changes over an extended period of time will reduce the impacts on agencies. This will help agencies to make the necessary changes in policies, procedures, staffing, training, and materials to implement the guidelines.
  • The evaluation methods should be implemented in a manner that recognizes the potential for changes in sign visibility that can occur between evaluation periods. There are many different events and occurrences that may lead to a decrease in sign visibility. Examples include:
    • Sign removal due to vandalism or crash impact.
    • Physical damage to the sign face (which may or may not be visible in daytime conditions).
    • Sign sheeting deterioration.
    • Growth of brush or vegetation.
• Tort Impacts
  • The specifics of the MUTCD language will have a significant impact on the extent of the tort liability impacts on agencies. The greater the level of detail in the MUTCD language, the greater the expected tort exposure for agencies.
  • Sign visibility and/or sign retroreflectivity has not generally been a significant tort issue in the past.

It should be noted that most of the participant discussion in the workshop focused upon the negative impacts of revising the MUTCD. The extent of negative impacts will vary from agency to agency, depending upon the current sign replacement practices in individual agencies. The negative impacts are expected to be smaller for those agencies that currently have effective sign replacement practices. It may not be appropriate to expect the FHWA to shoulder the fiscal impacts for those agencies that have not implemented effective sign replacement practices. There is also the potential for positive impacts from improved signing, including lower overall sign costs due to more effective sign replacement strategies and improved safety due to better sign visibility.

UNANSWERED QUESTIONS AND RESEARCH NEEDS

In addition to identifying various impacts associated with the visibility/retroreflectivity concept, the workshop participants asked numerous questions related to minimum retroreflectivity levels. The facilitators were able to answer most of these questions, but there were several questions that have not yet been addressed in the research program. These are listed below.

• What is the impact of ambient lighting on the visibility of signs?
  • Can intersection and street lighting provide sufficient luminance without retroreflectivity?
• Should minimum levels represent best case, typical case, or worst case scenarios?
• How will agencies develop accurate information on sign sheeting service life as a function of sheeting type, exposure direction, color, and other factors?
  • What is the impact of product lines changes on previous data about sign service life?
• What driver characteristics are of greatest concern?
  • How does driver age relate to the types of vehicles driven?
  • How many older drivers actually drive at night?
• How can agencies stop the trend of headlamps directing less illumination towards signs?
  • It is worth noting that the participants felt that it is not appropriate for agencies to assume the increased costs of improving the infrastructure that result from changes in automobile manufacturing standards. Headlamp performance changes every few years while signs that agencies install are intended to last at least 7-10 years, often longer. Participants felt that headlamp changes that impact traffic control device performance should be limited or better coordinated with the transportation agencies. A few participants even suggested that automobile manufacturers should provide funding for traffic control device improvements when changes are made.

WORKSHOP MUTCD LANGUAGE RECOMMENDATIONS

When the 2000 MUTCD was released, it contained a section on minimum retroreflectivity levels (Section 2A.09) that was reserved for future text based on FHWA rulemaking. One of the objectives of the workshops was to have the participants in each of the workshops develop recommended language for this section.

About half way through the morning discussion (following the discussion on identifying the major issues associated with minimum retroreflectivity levels), the facilitators asked the participants to develop the recommended MUTCD language. As a starting point, the discussion began with MUTCD language that had been developed by the facilitators. One version of the initial language was used for the first three workshops and a revised version was used for the last workshop. Both initial versions are presented at the beginning of Appendix H. Approximately an hour of the workshop was devoted to revising the initial MUTCD language so that it was generally acceptable to the participants in a particular workshop. After each workshop indicated a general consensus on the language it had developed, the facilitators distributed copies of the prior workshops' recommended MUTCD language. This generally led to a few minor additions to a workshop's recommended language. The resulting workshop recommendations for MUTCD language are presented in Appendix H.

There are similarities and differences in the recommended language developed by each workshop. The first three workshops elected to develop language for the section that was reserved for future text, although all three changed the title to a visibility emphasis instead of a retroreflectivity emphasis. The fourth workshop elected to revise the existing language in Section 2A.08, which addresses retroreflectivity and illumination, instead of adding a new section. All four workshops included language indicating that agencies should provide reasonable nighttime visibility of signs. All four workshops included a list of potential implementation options in the recommended language. Table 6 lists the options that were included by each workshop.

Three of the workshops included a list of signs in the MUTCD language that could be exempted from an agency's process for providing reasonable nighttime sign visibility. Participants gave several reasons for potentially exempting certain signs from visibility and/or retroreflectivity guidelines, including:

• Some signs have internal or external sign lighting and do not require any level of retroreflectivity for nighttime visibility. This is common for freeway guide signs and some mast-arm mounted street name signs.
• Some signs apply to situations where traffic is stopped or moving at very low speeds. Examples include:
  • Parking, Standing, and Stopping Signs (Series R7 and R8).
  • Street Name Signs (D3) on local roads with speed limits of 30 mph or less.
• Some signs are intended for pedestrians and bicycle users that do not require the same level of minimum retroreflectivity as signs intended for motorized vehicles. Examples include:
  • Walking/Hitchhiking/Crossing (R9, R10-1 through R10-4b).
  • Bikeways, including shared-use paths and bicycle lane facilities.
  • Some signs are provided for informational purposes only and may not be considered critical signs. Examples include:
  • General Information (I Series).
  • Specific services signs.
  • Recreational/Cultural Interest signs.
  • Blue D6 and D9 series signs.
  • Adopt-A-Highway.
  • Tourist-Oriented Directional Signs (Chapter 2G).

There are some significant differences in how the individual workshops approached the development of MUTCD language.

• The Lakewood workshop presented the implementation methods and sign exclusions as support statements. The other workshops presented the methods in Guidance or Option statements.
• All four workshops included a statement that sign replacement should not be based on retroreflectivity alone.
• All four workshops referenced a supplemental document.

POST-WORKSHOP FINDINGS

During the workshops, some of the participants indicated that some professional societies have developed official positions or policies on minimum levels of retroreflectivity. After the workshops were completed, the facilitators contacted several organizations to identify their official positions or policies on this issue. Several of the organizations responded and their positions/policies are presented in Appendix G. The presence of these policies indicate that many professionals and professional organizations recognize the importance of nighttime visibility and retroreflectivity, and that many organizations are following the development of federal guidelines related to nighttime visibility for traffic signs.