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Publication Number: FHWA-HRT-07-042
Date: April 2007
Maintaining Traffic Sign Retroreflectivity: Impacts on State and Local Agencies
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2. Traffic Sign Costs
The most basic way to look at the impacts on State and local agencies imposed by establishment of minimum maintained traffic sign retroreflectivity levels is to analyze the change in cost for an individual sign. The sections below isolate the various elements of sign cost, provide some estimates of the cost differences between various materials, discuss the effect of service life, and summarize other influences on sign cost.
2.1. Elements of Sign Cost
There are costs associated with the design, fabrication, installation, and maintenance of a traffic sign as a result of the materials, labor, and equipment needed. The major elements include.
In analyzing the impacts, it is necessary to isolate those cost elements that are truly affected by the proposed minimum levels of retroreflectivity. On the assumption that agencies will be able to spread the efforts to upgrade non-compliant signs over a 7-year or 10-year implementation period, the most significant additional cost becomes that of the sign face materials. Associated with the above assumption is that most replacements will take place under planned maintenance cycles. Thus, there should be no additional costs to the agencies for labor and time required to physically replace signs. An assumption is also made that agencies are currently following the MUTCD guidance in Section 2A.22 which recommends night-time inspections. There may be additional costs to agencies for equipment modifications to work with alternative sheeting materials, for conducting training for staff on working with these materials, and for labor and equipment related to new sign management processes and procedures. It is difficult to estimate the magnitude of the additional costs on a per sign basis, but they are considered to be a small percentage of the total cost of a sign.
2.2. Sign Cost Updates
The most significant impact associated with improving the night visibility of a sign is the difference in the cost of the sign sheeting material selected. There are limited data available on the types of materials currently being used by State and local agencies, so a general analysis of cost impacts was undertaken. Table 2 provides a rough approximation of unit cost differences, in dollars per square foot ($/ft2) of sign face, for available materials by ASTM designation.11 These numbers reflect the upward side of the various reported costs for available sign materials.
Upgrading sign sheeting materials from Type I to Type III or Type IV, which is the most likely change that would result from establishment of minimum maintained retroreflectivity levels, will result in an increase of approximately $0.75/ft2. For a typical 36" x 36" sign, that would translate to a $6.75 increase in the cost of the sign sheeting material. While this is a 100 percent increase in the cost of the sheeting (from $6.75 to $13.50), the total cost for an installed sign is estimated to be $100-200, (based on average reported costs in Reference 6, updated for inflation) which implies that the $6.75 increase in sheeting cost translates to a 3 to 7 percent increase in installed cost. All other costs for the sign and the replacement activities would remain unchanged. The overall costs to an agency would be dependent upon the total number of signs in their inventory and the degree of change made.
2.3. Sign Life Cycle Costs
The best measure of the cost of a sign to an agency is its life-cycle cost, under which the total cost is distributed over the years of useful life that the sign will provide. Generally, signs are expected to provide adequate detectability and legibility for 7 to 15 years, depending on the sign sheeting, but there are currently no specific criteria or models that can definitively predict service life. Estimates of the life-cycle cost of a sign are difficult to establish, but important to consider for long-term budgeting.
To illustrate the influence of service life, assume that an agency plans to upgrade 1,000 yellow 36" x 36" warning signs. Three materials are considered for these signs: Type X, Type Y, and Type Z. These materials vary in cost and expected service life as shown in Table 3. Over a 30-year period, it would be necessary to replace Type X signs five times after initial installation. The Type Y materials would require two replacements and the Type Z material only one replacement during the 30 years. The cumulative sign sheeting costs indicate that it might actually save the agency money to select a higher cost material with a longer service life. The most dramatic outcome occurs when total installation costs are added to the sign sheeting costs. Assume an average cost of $150 to install or replace a 36" x 36" warning sign. This includes labor, hardware, administrative expenses, and other costs, and is incurred each time the sign reaches the end of its useful life. In this example, signs manufactured with Type X material must be installed six times, but only three times for Type Y and twice for Type Z. The total costs of the sign and replacement operations clearly illustrate that what appears in the beginning to be the more expensive option is the less expensive option in the end. In reality, the costs in this example would increase due to inflation and other external changes that might affect the service life or unit costs of the materials. Table 4 illustrates how an annual increase of 3.5 percent in sign material, fabrication, and installation costs would affect the live cycle costs of the example.
2.4. Factors Influencing Sign Costs
Agencies that have historically used Type I sheeting for the majority of their signs are likely to experience higher implementation costs than will agencies that have historically used Type II, or III sheeting. Initial cost increases may even be higher if agencies opt to use microprismatic sheeting (Types IV, VII, VIII, IX and X). In addition to the cost differences between sheeting types, there are other factors that can influence the implementation costs incurred by an agency, including:
It is the responsibility of highway agencies under the MUTCD to maintain acceptable levels of night visibility for in-place traffic signs. The minimum maintained retroreflectivity levels for traffic signs provides only the starting point for processes that will lead to improved night visibility over the road network. An agency may choose to define "acceptable" as some level above the minimum levels to better serve the needs of the driving public. For example, retirement communities may wish to use brighter signs to better accommodate older drivers. It is hoped that agencies will adopt retroreflectivity levels for traffic signs that are commensurate with the visual requirements of roadway users based on actual local conditions.
Topics: research, safety, visibility and retroreflectivity
Keywords: research, safety, retroreflectivity, maintained retroreflectivity, minimum maintained retroreflectivity, impact, impact assessment, impacts analysis, national impact assessment
TRT Terms: reflective signs, retroreflectivity