Discussion of Other Comments
In addition to the five major issues discussed in the previous section, FHWA also received comments that can be grouped into the following three topics:
(6) Assessment methods;
(7) Blue and brown signs; and
(8) Minimum retroreflectivity levels.
This section contains a discussion of each of these topics.
(6) Assessment methods:
The FHWA received comments from the AASHTO, NCUTCD, ATSSA, AHAS, AAA, AARP, AHUA, ARTBA, Maryland and Wisconsin DOTs, and several counties in Illinois regarding the assessment and management methods for maintaining sign retroreflectivity as proposed in the GUIDANCE statement of the SNPA. The AASHTO and several State DOTs did not support actual measurement of signs as one of the methods, but supported visual nighttime inspections, blanket replacement, control signs, and expected sign life methods.
The city of Plano, Texas and a private citizen suggested that the numerical values in Table 2A-3 should only apply to Method B: Measured Sign Retroreflectivity. Those commenters suggested that for all other methods where subjective judgment is used, such as visual nighttime inspection, the table should serve as guidance for local offices to reject and accept signs.
Finally, the NCUTCD, the Illinois Association of County Engineers, and the DeWitt County, Illinois Highway Department suggested adding additional language to the GUIDANCE statement to explicitly, rather than implicitly, state that other assessment methods based on engineering study can be used to assess sign retroreflectivity. The FHWA believes that the final rule provides several assessment or management methods that agencies can choose from, based on the method that best fits the agencies' resources and needs. An agency can choose to use either assessment methods or management methods, or a combination; however, agencies should develop a method in such a way that it corresponds to the values in Table 2A-3. The methods have been developed to provide flexibility for agencies for addressing their local conditions. To address the comments received regarding the types of assessment methods that should be used, FHWA clarifies the GUIDANCE statement by adding a sixth method to the list of assessment or management methods titled “Other Methods,” which explicitly states that other methods developed based on engineering studies can be used.5
(7) Blue and brown signs:
In the SNPA, FHWA asked for comments on the need for retroreflectivity levels to be developed for signs with blue and brown backgrounds.6 The Maryland State Highway Administration suggested that recommended minimum retroreflectivity levels be established for blue-background signs and that those levels apply to certain signs such as Hospital, EMS, Ambulance Station, and Emergency Medical Care signs, whose nighttime readability can be important. The combined letter from a representative of AAA, AARP, and AHUA, and one comment letter from a sign manufacturer stated that blue and brown signs are intended for use both day and night, and that motorist safety, particularly for older drivers, would be enhanced by including minimum retroreflectivity levels for blue and brown signs. The commenters acknowledged that if blue and brown signs are being excluded because there is a lack of data on which to base a requirement, a “placeholder” could be included in the MUTCD until more data is available and the table of minimum levels can be updated.
The FHWA is currently studying blue and brown minimum sign retroreflectivity levels. Because the study has not been finalized and FHWA did not analyze the costs associated with the sign retroreflectivity of blue and brown signs in the economic impacts study, minimum retroreflectivity levels for blue and brown signs are not included in the MUTCD at this time. At the conclusion of FHWA’s study on this topic, the results may indicate a need to pursue such a requirement. If so, updates or changes to Table 2A-3 would be subject to the public rulemaking process before FHWA could add blue and brown minimum retroreflectivity levels.
(8) Minimum retroreflectivity levels:
Several of the commenters, including AASHTO, NACE, the Illinois and Indiana Associations of County Engineers, DeWitt County, Illinois Highway Department, the North Carolina DOT and the Maryland State Highway Administration suggested that the data within the table were not precise, and reflected data that were developed based on assumptions and varying characteristics.
The FHWA acknowledges that the data are based on some assumptions and varying characteristics; however, they are based on the latest science and empirical-based research emphasizing older drivers.7 The supporting research reflects the best information at this time. One of the key aspects to the research supporting the minimum retroreflectivity levels is that it was based on field studies under conditions on a closed course facility that represented real roadway scenarios to the maximum extent possible without jeopardizing safety. Research subjects were recruited and participated in the research, which ultimately developed cumulative distribution profiles for luminance levels needed to accommodate the legibility of older drivers. These luminance levels were then used in conjunction with computer modeling to determine the retroreflectivity needed under a variety of roadway conditions. The computer modeling allows analyses of an infinite set of roadway scenarios, but is based on the luminance levels derived through the human factors research supported by FHWA.
After the research was completed, FHWA held national workshops, which included nighttime inspections of signs at various retroreflectivity levels. The participants of the workshops evaluated the signs at night using a visual inspection technique. The results of this effort helped confirm that the minimum retroreflectivity levels in Table 2A-3 are appropriate.
The NCDOT suggested that a tiered system be applied to the retroreflectivity levels, similar to the tiered system used for letter heights and sign sizes based on roadway classification.8 The NCDOT commented that retroreflective sign applications for lower speed, lower volume roads should be coordinated with lower retroreflectivity values.
The FHWA believes that the values shown in the table are applicable to all classifications of roads, including lower volume and slower speed roadways. The retroreflectivity levels are based on the legibility design threshold level as specified in Section 2A.14 of the MUTCD (40 feet of legibility per inch of letter height). Therefore, the size of the sign, and the message on the sign, play a key role in the retroreflectivity levels. Smaller signs have smaller messages, which mean drivers need to be closer to the signs to read them. As the distance between the sign and the vehicle decreases, the efficiency of retroreflectivity materials generally decreases, meaning that more retroreflectivity is needed. This often outweighs the increased illumination available from the vehicle headlamps. The minimum retroreflectivity levels were designed to be easy to implement, without added complexities such as a tiered system based on letter heights and sign sizes. However, with the proper support (i.e., an engineering study), and using the values in Table 2A-3 as minimum maintained retroreflectivity levels, there is flexibility in this final rule and the associated MUTCD language that allows for an agency to develop a more complex set of minimum retroreflectivity levels, if it chooses to do so. Such levels cannot be below the minimums in Table 2A-3.
As mentioned in item 3 under Major Issues, a few commenters such as NACE, the NCUTCD and others, believed that Table 2A-3 and its title should be referred to as “Recommended.” The FHWA believes that it is inappropriate to include “Recommended” in the title of a table that is referenced in a STANDARD statement of the MUTCD. In addition, the word “Recommended” implies Guidance, rather than a Standard, and would therefore be confusing.
ATSSA, the AHAS and the MNDOT agreed with eliminating Type I material for ground-mounted signs, and they also agreed with eliminating Types I, II, and III for overhead guide sign legends. These commenters felt that prohibiting the use of these less efficient retroreflective materials would substantially improve the nighttime driving environments, especially for older drivers with a variety of visual impairments. ATSSA also supported including Type X materials so that all currently defined American Society of Testing Materials (ASTM) Type designations that are used for traffic signs will be included in the MUTCD.
The NCDOT disagrees with any retroreflective requirement for illuminated signs. Their reasoning is that the assessment and management methods used to maintain retroreflectivity do not address signs with illumination and that Section 2A.08 does not require retroreflectivity for illuminated signs.
Illuminated signs do need to meet the minimum retroreflectivity requirements because there are times that the signs may not be illuminated due to power failure. Previous research has shown that overhead signs can be effective without lighting, as long as the appropriate retroreflective sheeting materials are used to fabricate the sign.9 With this knowledge, many agencies have elected to use more efficient retroreflective sheeting on overhead guide signs without sign lighting, citing adequate visibility and concerns about energy use and light pollution (although sign lighting may continue to be used in areas of complex surroundings and/or roadway geometries). The minimum retroreflectivity levels in Table 2A-3 in the MUTCD prohibit the use of less efficient reflective materials for overhead signs so that agencies do not use them. As a result, agencies are more likely to select appropriate materials to meet nighttime driving requirements.
One supplier of overhead sign lighting systems and 22 citizens suggested that lighting of overhead signs should be mandatory. This final rule does not change the existing MUTCD language recommending lighting for overhead signs. Mandating lighting for overhead signs is outside the scope of this rulemaking.
One sign manufacturer suggested that retroreflectivity levels measured at 0.5 degree observation angle be included. As discussed in item #12 of the SNPA, research has been completed that supports moving toward the 0.5-degree concept and the ASTM has started working toward a revision to its specifications to describe 0.5-degree measurements.10 The FHWA believes that it is not practical to implement minimum retroreflectivity levels based on an observation angle of 0.5 degrees until measuring devices become more readily available, and the ASTM completes its work developing a standard measurement specification. At that time there may be a need for an alternative table and a transition period established while the 0.2-degree measurement geometries and devices are phased out. If so, these changes will be introduced through public rulemaking procedures described earlier for MUTCD changes or additions.
5As defined in the MUTCD, an engineering study shall be performed by an engineer, or by an individual working under the supervision of an engineer, through the application of procedures and criteria established by the engineer. An engineering study shall be documented. In accordance with the text heading GUIDANCE in the MUTCD, deviations to a recommended practice are allowed if engineering study indicates the deviation to be appropriate..
6Blue signs are generally described as informational signs, and include evacuation route and road user signs. Examples include hospital, specific service signs (food, gas, lodging, camping, and attraction) and tourist-oriented directional signs. Brown signs, which are also informational signs, are primarily recreational and cultural interest area signs.
7Carlson, P.J. and H.G. Hawkins. Minimum Retroreflectivity Levels for Overhead Guide Signs and Street-Name Signs. FHWA-RD-03-082. U.S. Department of Transportation, Federal Highway Administration, Washington, DC. This document is available at the following Web address: http://www.tfhrc.gov/safety/pubs/03082/index.htm
8Part 2 of the MUTCD includes a table titled, “Table 2B-1 Regulatory Sign Sizes” that includes sign sizes for conventional roads, expressways, freeways, and oversized as well as minimum sign sizes. Generally, sign sizes for conventional roads are smaller than those for expressways or freeways.
9Carlson, P.J. and H.G. Hawkins. Minimum Retroreflectivity Levels for Overhead Guide Signs and Street-Name Signs. FHWA-RD-03-082. U.S. Department of Transportation, Federal Highway Administration, Washington, DC. This document is available at the following Web address: http://www.tfhrc.gov/safety/pubs/03082/index.htm
10The ASTM E12 committee is working to develop a standard measurement specification for 0.5 degree instruments. The committee is using ASTM E1709 as a template (ASTM E1709 is the standard measurement specification for 0.2 degree instruments). More information is available at www.astm.org.
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