Preliminary Economic Impacts of Implementing Minimum Levels of Pavement Marking Retroreflectivity
FINAL REPORT
Publication No. FHWA-SA-08-010
Chapter 2: Basic Input Data
The first step in conducting an economic analysis of minimum pavement marking retroreflectivity guidelines is to identify key input data that serve as the basis for the initial analysis, and which have the potential to be adjusted at a later time as more specific information becomes available. The input data gathered for the analysis include:
- Quantities of pavement markings subject to the minimum retroreflectivity guidelines, including the quantities of each type of material. This information includes:
- An inventory of roadway mileage, stratified by area type (rural or urban), functional classification (interstate, freeway, expressway, principal arterial, minor arterial, collector, and local road), and jurisdictional ownership (federal, state, county, and city),
- A count of average laneage for all relevant roadway categories, and
- Estimates on striping configurations for two- and three-lane undivided highways (related to passing zone policies);
- Service life data for both white and yellow marking materials based on the amount of time that the materials can maintain a specified retroreflectivity level;
- Typical replacement costs for pavement marking materials, stratified by jurisdiction (federal, state, county, and city); and
- Potential retroreflectivity levels that would define the replacement thresholds.
Pavement Marking Quantities
The total quantity of pavement marking subject to the minimum retroreflectivity guidelines is determined through a multi-step effort which includes estimating the total mileage by functional class, developing typical pavement marking configurations for each functional class, and calculating the total miles of pavement markings by material using information on material type usage.
Roadway Mileage
The total miles of rural and urban roadway by functional classification were obtained from FHWA's Highway Statistics 2003 Table HM-20 (for the total system) and Table HM-50 (broken down by jurisdiction) (2). For each functional class, the data were further divided into mileage by the number of lanes (using Highway Statistics Table HM-55). The use of the roadway mileage in the analysis procedure is described in more detail in the next chapter.
Pavement Marking Configurations
It should be noted that the researchers also assumed that the minimum retroreflectivity guidelines would apply only to long lines, not any other types of pavement markings such as stop/yield lines, crosswalks, words, or arrows. Furthermore, the only long lines included in the analysis are those that are required by the MUTCD. As an example, low-volume roads (less than 6,000 vpd) do not require edge line markings. Therefore, this analysis does not include edge line markings for low-volume roads.
Typical striping configurations for each functional classification are shown in Appendix A. These configurations are based on MUTCD guidance and the assumptions listed below.
- All longitudinal markings are 4 inches wide.
- All lane line patterns consist of a 10 ft stripe followed by a 30 ft gap.
- Rural minor arterials, rural major collectors, and urban collectors have sufficiently low average daily traffic (ADT) (less than 6,000 vpd) that they do not require edge lines.
- Rural major collectors and urban collectors have sufficiently low ADT (less than 6,000 vpd) that they do not require center lines unless they have three or more lanes. The center lines on segments with ADT greater than 6,000 vpd consist of double-solid yellow lines.
- Rural minor collectors, rural local roads, and urban local roads have sufficiently low ADT (less than 6,000 vpd) that they do not require any pavement markings.
These striping configurations were then combined with the mileage estimates to obtain an estimate of the total miles of pavement markings. The next chapter provides more details about how this information was used in the actual analysis.
Pavement Marking Material Quantities
There are several types of pavement marking materials in use around the United States. Each type of material has cost and service life implications which are an important part of an economic analysis. Unfortunately, the researchers are not aware of any databases of significance that provide a useful estimate of the quantities of each type of material by class of roadway. However, there have been some surveys of practices that give some indications of the use of various materials (3,4). The authors used the information from these surveys to select typical distributions of material types for analysis. Several different material type scenarios were analyzed. These scenarios are described in the analysis chapter of this report.
Pavement Marking Service Life and Material Cost
As with the other quantities, there are no national databases of pavement marking material use and costs. Therefore, the researchers relied upon the most recently available information to populate the cost information. The researchers only included material types in the analysis where recent and sufficient data were available to generate representative cost estimates. The material types used in the analyses total approximately 95 percent of the pavement markings installed in the United States (by mileage) (3). The costs represent contractor-installed costs. In many cases, agency-installed costs can be much lower. However, there is substantial variation in costs around the country. Furthermore, factors such as rising energy costs, new environmental restrictions, and raw material availability will have a significant impact on pavement marking costs in the future. The analysis tool provides a function that allows users to enter their own pavement marking material costs.
The costs ($/ft) for the pavement marking materials used in this report were obtained from a variety of sources, including a 2002 NCHRP synthesis (3), a 2005 unpublished FHWA report (4), a 2007 TxDOT report (5), and the 2007 FHWA workshops on minimum pavement marking retroreflectivity (held in Denver and Pittsburgh during the summer of 2007) (6). For the economic analysis, representative cost estimates were generated as base costs and then increased and decreased by 25 percent to provide a range of cost data to use in the analysis. These costs are based on figures representing contractor-installed markings. They include the total costs for installation (e.g., materials, labor, overhead, lane closures, etc.). Table 1 summarizes the cost data used in the economic analysis.
| Material | Cost ($/linear ft) for jurisdiction (Low/Base/High) | |
|---|---|---|
| Federal / State | City / County | |
| Epoxy | $0.23/0.30/0.38 | $0.45/0.60/0.75 |
| Methyl Methacrylate | $0.94/1.25/1.56 | Insufficient data |
| Tape (profiled) | $2.06/2.75/3.44 | $3.00/3.00/4.00 |
| Thermoplastic | $0.26/0.35/0.44 | $0.38/0.50/0.63 |
| Waterborne Paint | $0.05/0.06/0.08 | $0.11/0.15/0.19 |
The service life estimates for each material type was generated from an FHWA-sponsored research effort (7). Although the report was not published, it represents one of the most detailed field efforts that investigated the service life of pavement markings applied in their natural orientation (i.e., longitudinally as opposed to a transverse application, which is a common way to test markings but provides only indirect service life information) and as a function of retroreflectivity levels (7). Only service lives for the FHWA research recommended minimum retroreflectivity levels were provided explicitly in the source document (7). The regression model parameters used to determine these service life values were used to determine service life values for a range of minimum retroreflectivity levels. The regression models provide service lives in terms of cumulative traffic passes (CTPs). This information was used to develop service life values in months for use in the spreadsheet as a function of the marking retroreflectivity level. The service life values used in the economic analysis are contained in one of the worksheets (marking specifications) of the analysis tool. The individual sheets of the analysis tool, which is described in detail in the next chapter, are presented in Appendix B, where the service life values used in the analysis can be observed.
Potential Retroreflectivity Values
As one would expect, the results of an economic assessment of minimum pavement marking retroreflectivity levels will depend upon the threshold criteria that are used to define the end of service. However, the threshold criteria have not yet been set. Therefore, the researchers have reviewed recent proposals for minimum pavement marking retroreflectivity and conducted the analysis for a range of minimum retroreflectivity levels.
Over the last 15 or 20 years, numerous research efforts have evaluated pavement marking retroreflectivity. Using the results from these research efforts, there have been a few specific proposals for minimum levels of pavement marking retroreflectivity. This chapter describes these minimum retroreflectivity proposals and the process used to develop each proposal. It is important to note that none of the minimum retroreflectivity proposals has been published in the technical literature in a manner that would make it accessible to the profession.
Internal FHWA Initial Research Recommendations
In 1999, an internal FHWA report presented the initial research recommendations for minimum levels of retroreflectivity (8). These levels are shown in Table 2. In this report, the authors compiled information from nine previous studies heavily focused on pavement retroreflectivity. However, to account for deficiencies present in the available information, two new investigations were also devised. Taken together, the research presented in the report provides a comprehensive view of previous research, as well as a foundation on which FHWA research recommendations for minimum retroreflectivity are based.
| Option 1 | Non-Freeway, ≤ 40 mph |
Non-Freeway, ≥ 45 mph |
Freeway, ≥ 55 mph |
|
|---|---|---|---|---|
| Option 2 | ≤ 40 mph | ≥ 45 mph | ≥ 60 mph, > 10K ADT |
|
| Option 3 | ≤ 40 mph | 45-55 mph | ≥ 60 mph | |
| With RRPMs |
White | 30 | 35 | 70 |
| Yellow | 30 | 35 | 70 | |
| Without RRPMs |
White | 85 | 100 | 150 |
| Yellow | 55 | 65 | 100 | |
Source: Reference (8). |
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The research retroreflectivity recommendations in the internal FHWA report were based on an FHWA-sponsored research study focused on pavement marking retroreflectivity (9). This report, also unpublished, proposed the minimum retroreflectivity levels shown in Table 3. Although the report was not published by the FHWA, Zwahlen did publish the research results in a peer-reviewed journal paper (10).
| Speed (mph) | Minimum Required RL (mcd/m2/lx) | |
|---|---|---|
| Without RRPMs Preview = 3.65 sec |
With RRPMs Preview = 2 sec |
|
| 0-25 | 30 | 30 |
| 26-35 | 50 | 30 |
| 36-45 | 85 | 30 |
| 46-55 | 170 | 35 |
| 56-65 | 340 | 50 |
| 66-75 | 620 | 70 |
FHWA Pavement Marking Workshop Recommendations
In the fall of 1999, the FHWA sponsored a series of three public agency workshops on minimum pavement marking retroreflectivity. These workshops presented the research and recommendations summarized in the internal FHWA report and solicited input from the 67 public agency participants. An unpublished report describes the workshops and the minimum retroreflectivity recommendations that are based on the input received during the workshops (11). The report presented two alternatives for the format of the retroreflectivity guidelines — one based on road speed and one based on road classification. These recommendations are presented in Tables 4 and 5. These recommendations are not based on the specific results of any single research effort, but represent a general consensus of opinion from the local and state public agency personnel that participated in the workshops.
| Marking Color | Minimum RL a (mcd/m2/lux) for Indicated Speed b | ||
|---|---|---|---|
| ≤ 30 mph | 35-50 mph | ≥ 55 mph | |
| White | Presence c | 80 | 100 |
| Yellow | Presence | 65 | 80 |
Notes: |
|||
| Marking Color | Minimum RL a (mcd/m2/lux) for Class of Roadway | ||
|---|---|---|---|
| Local and Minor Collector |
Major Collector and Arterial |
Highways, Freeways, and all roads ≥ 55 mph |
|
| White | Presence b | 80 | 100 |
| Yellow | Presence | 65 | 80 |
Notes: |
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ATSSA Recommendations
In the summer of 2004, the American Traffic Safety Services Association (ATSSA) undertook an internal effort to develop recommendations for minimum levels of pavement marking retroreflectivity. The recommended minimum levels are shown in Table 6. These recommendations were developed through the ATSSA Pavement Marking Committee and approved by the ATSSA Board of Directors. As with the FHWA pavement marking workshop recommendations, the ATSSA recommendations are not based on any specific research effort. Rather, they represent a consensus of those involved in providing traffic safety services. As with the other minimum retroreflectivity recommendations, the ATSSA recommended levels have not been published.
| Posted Speed (mph) | ≤ 50 | ≥ 55 |
|---|---|---|
| Retroreflectivity (mcd/m2/lux) | 100 | 125 |
| Notes: Retroreflectivity levels are based on 30 meter geometry. Retroreflectivity levels apply to both white and yellow markings. |
||
An interesting aspect of the ATSSA recommendations is that they suggest that the same numerical minimum value be applied to both white and yellow markings. This recommendation is based on the factors listed below.
- Yellow longitudinal markings receive less light from headlamps than white longitudinal markings because they are on the left side of a vehicle and headlamp beam patterns focus more light toward the right side of the vehicle.
- The measure of retroreflectivity is a metric that can be used to quantify visibility. As such, a minimum retroreflectivity level defines a minimum visibility level. Assuming that the visibility of white and yellow markings should be the same, then their retroreflectivity level should be the same, despite the lower retroreflectivity levels typically associated with yellow markings.
- The retroreflectivity level should not be reduced based simply on the fact that a yellow marking fabricated from the same basic material as a white marking has a lower retroreflectivity value than the white marking of the same material – it is possible to utilize yellow marking materials that will achieve the same retroreflectivity as a given white material.
Summary of Minimum Retroreflectivity Guidelines
Table 7 presents a summary of the retroreflectivity recommendations from the efforts described above. The summary shows that most of the research recommendations are based on minimum levels for white and yellow markings that are near a value of 100 mcd/m2/lx. The summary also shows that speed is a popular classification metric to distinguish between different levels of minimum pavement marking retroreflectivity.
| Effort | Speed (mph) | Recommended Retroreflectivity (mcd/m2/lx) | |
|---|---|---|---|
| White | Yellow | ||
| FHWA Initial Research |
≥ 60 | 150 | 100 |
| 45-55 | 100 | 65 | |
| ≤ 40 | 85 | 55 | |
| FHWA Workshops |
≥ 55 | 100 | 80 |
| 35-50 | 80 | 55 | |
| ≤ 30 | Presence | Presence | |
| ATSSA | ≥ 55 | 125 | 125 |
| ≤ 50 | 100 | 100 | |
| Average | Higher Speed | 125 | 102 |
| Moderate Speed | 93 | 73 | |
| Lower Speed | 85 | 55 | |
The researchers used the summarized research recommendations to define minimum pavement marking retroreflectivity levels to use in the economic impacts analysis. Three sets of minimum pavement marking retroreflectivity levels were developed for the economic analysis. A base case was developed using values that best represent the summarized research recommendations. Two additional cases were also developed using values approximately 20 percent lower than the base case and values approximately 20 percent higher than the base case. For each case, there are low-, moderate-, and high-speed groups, each of which are associated with specific roadway functional classifications. Table 8 shows the specific values used in the economic analysis.
| Case | Speed | Retroreflectivity (mcd/m2/lx) | |
|---|---|---|---|
| White | Yellow | ||
| Low Values | High Speed | 100 | 85 |
| Moderate Speed | 85 | 55 | |
| Low Speed | 70 | 45 | |
| Base Values | High Speed | 125 | 100 |
| Moderate Speed | 100 | 70 | |
| Low Speed | 85 | 55 | |
| High Values | High Speed | 150 | 125 |
| Moderate Speed | 125 | 85 | |
| Low Speed | 100 | 65 | |
