Because traffic signs play a significant role in the safe and efficient operation of the nation's highways, it is important that they be in good condition. As they age, signs can lose their color and their ability to reflect light, which can make them difficult to see and read. Before 1993, the Manual on Uniform Traffic Control Devices (MUTCD) stipulated that signs must be "reflectorized or illuminated" but provided no guidelines. Before the MUTCD underwent a congressionally mandated revision, the Federal Highway Administration (FHWA) "initiated and conducted a comprehensive research and demonstration program to address the various retroreflectivity performance issues." Several research studies on these performance issues resulted from this FHWA program.

One such study sought "to assess the national impact of implementing the FHWA proposed guidelines for minimum levels of retroreflectivity of traffic signs, on State and local highway agencies." Sunil Taori and Hugh W. McGee reported the study's results in "Impacts of Maintaining Traffic Signs Within Minimum Retroreflectivity Guidelines," a paper submitted for presentation at the 77th Annual Meeting of the Transportation Research Board (January 1998).

The signs within local jurisdictions did not fare as well in the analysis as those belonging to state agencies. Overall local signs were older, they met fewer minimum retroreflectivity guidelines, and more of them would need replacement at a higher cost. The study estimated that replacement costs nationwide would be about $144 million for local agencies and $32 million for state agencies.

METHOD

Researchers asked a number of state and local agencies to participate in the study. The FHWA provided them hand-held retroreflectometers to measure the retroreflectivity of signs currently in use.

Highway signs are classified primarily by function and color (four groups) and by sheeting material (four groups). The FHWA has proposed minimum retroreflectivity values for signs in each group. Researchers asked agencies to evaluate the retroreflectivity of a sample of their signs based on these guidelines. The agencies then submitted a report that included this data and discussed the impact of replacing signs using the guidelines--including the cost of replacement. The agencies were also asked to comment on the hand-held retroreflectometer's handling ease.

RESULTS

Sixteen state agencies and nine local agencies participated in the study. Not all agencies submitted all the requested information, and some submitted data that was not requested for the study. In addition, "some agencies submitted retroreflectivity measurements that were highly questionable." These irrelevant or questionable data were not included in the analysis.

Results showed that "local jurisdictions have a significantly higher percentage of Type I [Engineering Grade (EG)] sheeting signs than the States." Type I sheeting has both lower reflectivity and a shorter life span than higher-grade sheeting materials. Local agencies also had a higher percentage of older signs (10-15 years or older). Typically, these signs "are not replaced as frequently as those under State control and are in service for longer durations than they should be."

As a result, "signs under local jurisdictions would, in general, have a higher replacement rate than those under States." More than 5 percent of the local signs in each group would need replacing, while less than 5 percent of state signs in each group would require replacement--with the exception of white-on-green guide signs. More than 9.5 percent of white-on-green state signs would need replacement, as compared with just 3 percent of those in local jurisdictions, primarily because states have a "significantly higher number" of these guide signs than do local jurisdictions. Almost 10 percent of the local "black-on-yellow/orange warning signs" ("the most crucial group of signs for local agencies") would require replacement, as well as about 8 percent of the "next crucial group," white-on-red regulatory signs (Stop, Yield, Do-Not-Enter, and Wrong-Way).

The cost estimate for replacing signs required "an estimate of sign densities (i.e. number of signs per mile)." Two state and seven local agencies provided data on sign densities; in total, "71,605 signs covered by 4,694 miles (7557 km) of State highways and 26,822 signs under 3,296 miles (5307 km) of local roads were included in the analyses." Several factors (labor and equipment costs, material type, etc.) affect the total cost of a traffic sign. Because price rates vary across jurisdictions, "it was difficult to derive an average cost of installing a new sign or replacing an old sign with a new one." As such, nationwide, "the final costs of sign replacement varied greatly."

Consequently, "the unit cost of sign installation [i.e., sign installed cost per unit area of the sign size] was selected as a basis to estimate the national cost of replacing signs not meeting the proposed minimum retroreflectivity values." The researchers found, "[T]he unit costs of installing new signs used for this study were: $9.00 per sq. ft. ($96.88 per sq. m.) for Type I material and $11.25 per sq. ft. ($121.09 per sq. m.) for Type III material." Cost estimates were tabulated for only Type I and Type III (High-Intensity (HI) Grade) sheeting materials, because no agencies submitted data that included either Type II or Type IV sheeting material signs.

Table 1 lists the costs of each of the four sign groups for both state and local jurisdictions, and Table 2 lists the total estimated national cost of replacing signs that do not meet minimum retroreflectivity guidelines.

As both tables indicate, local jurisdictions would incur higher replacement costs. It should be noted that cost estimates do not include the costs of removing and disposing of signs, nor do they reflect material recycling practices. In addition, most state and local agencies have an existing sign replacement program, which means sign replacement would likely not require additional personnel or equipment. Replacement is logically an ongoing project rather than a broad-scale, one-time effort. Most agencies replace signs on an as-needed basis. Therefore, the authors suggested that "many agencies . . . will not likely feel any additional impact of implementing the minimum retroreflectivity guidelines." However, some state and local agencies "estimated a significant impact on their budgets because of the perceived need for additional staff for sign inventory and inspections, and more equipment (reflectometers and even vehicles)." Others felt that despite higher initial costs, the long-term costs would not be any higher than normal.

Regarding the hand-held retroreflectometer's handling ease, most agencies found it "time-consuming and cumbersome."

LIMITATIONS

Sample sizes for the analyses were limited by the number of local agencies that responded to the survey (nine local as opposed to 16 state agencies). In addition, the data submitted did not include any from large cities. As a result, "the densities of sign for local jurisdictions available from the survey . . . may not accurately reflect the actual magnitude of number of signs per roadway mile, as the large cities normally have higher densities of signs than the participating jurisdictions."

CONCLUSIONS