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Clearview Typeface Supplement, English version

This submittal is made at the request of the Federal Highway Administration, Office of Transportation Operations in support of a request by the Pennsylvania Department of Transportation for approval to use the Clearview typeface on traffic control devices in lieu of FHWA Standard Alphabets for Traffic Control Devices based on the research of the Pennsylvania Transportation Institute and the Texas Transportation Institute.

September 2, 2004

Contents

Overview: Initial Assumptions & Problem Statement
Design Development
Results of Research and Evolution of the Design
The Clearview Type System
Letter and Word Spacing: Manual and Computer Based
Criteria for Updating the Standard Alphabets
Request for Use as an Approved Alternate Typeface for Highway Signs
General Application Guidelines
The Clearview Type System Alphabets
Letter Spacing Tables
Conceptual Applications
Clearview Tables 1-B through 2-W
Clearview Tables 3-B through 4-W
Clearview Tables 5-B through 6-W
Clearview Typeface Display

Credits

The Clearview Type System for traffic control devices was developed by a design team that included Martin Pietrucha, Ph.D. and Philip Garvey of the Pennsylvania Transportation Institute (PTI), Donald Meeker and Christopher O'Hara of Meeker & Associates, Inc., James Montalbano of Terminal Design, Inc., with supporting research by Gene Hawkins, Ph.D. and Paul Carlson, Ph.D. of the Texas Transportation Institute (TTI). Consultation on experimental design was provided by Susan T. Chrysler, Ph.D., formerly with the 3M Company and now with TTI. This type system is designed for signing all streets, highways, and other byways open to public travel.

Overview: Initial Assumptions & Problem Statement

The Clearview Type System was developed as the result of a research program aimed at increasing the legibility and recognition of road sign legends. The primary goal was to reduce the effects of halation (or overglow) for older drivers and drivers with reduced contrast sensitivity, when letters are displayed using high brightness retroreflective materials. To satisfy these objectives, it was necessary to identify ways to create a typeface that was more effective than E-modified for destination legends on freeway guide signs. A second component of the project was to compare the ease of recognition provided by mixed case displays (initial capital letter only) vs. all uppercase letters (Series D).

The initial research assumption was that four problems with current signage could all be solved with a typeface that was more effective for traffic control devices and guide signs. These problems include the need to upgrade signing to accommodate older drivers; questions about how motorists read sign legends with greatest speed, accuracy, and distance; and adding more information on the roadscape at locations that are currently heavily signed. Specifically:

Figure 1. An increase of 20% in letter height results in a 40-50% increase in overall sign area.

1. A major FHWA study published in 1994 recommended 20 percent increases in letter height using FHWA Standard Alphabets for Traffic Control Devices to accommodate viewing distance and reaction time requirements of older drivers. This is the 65 and older age group that by 2005 will number 36 million people or about one-fifth of the U.S. driving population. That 20 percent increase in letter height would result in a 40 to 50 percent increase in the overall area of a sign because the width of the panel would be extended as well. The design team theorized that if an appropriate typeface design were developed that could effectively increase legibility distance and recognition distance by 20 percent without an increase in capital letter height, all traffic control devices could be upgraded without the physical requirements for larger signs and sign structures.
   
   

   Figure 2. FHWA Series 3 Uppercase vs. Clearview 3-B mixed case.

   
   
2. If use of an optimized mixed case typeface proved more recognizable than all capital letters on guide signs and street name signs, there would be less need to make signs larger to accommodate older drivers while improving the basic performance of the sign.
   
   
3. If these typefaces eliminated visual massing of convergent points in strokes or bleeding with adjacent letters, the problems of halation or overglow could be reduced or eliminated for older drivers viewing signs with legends fabricated with high brightness materials on backgrounds with high contrast between legend and background.
   
   

   Figure 3. Overglow simulation with E-modified (left), Series D (center), and Clearview 5-W (right)

   
   
4. Cities and states are attempting to place more information on the roadscape for tourism-related activities as well as adding regulations, and signing for pedestrian safety in areas that are already densely packed with assemblies of guide and regulatory panels. If guide signs are improved, and the installations made more modular in design, the appearance of sign clutter may be reduced while increasing overall effectiveness of the collective installation.
   
   
5. Solving each of these problems was contingent on improving the legibility, recognition, and ease of understanding of road sign typography and providing a more consistent integration of sign components.
   
   
6. This typographic development program has taken nearly ten years and has included five separate, multi-part research studies by PTI and TTI. The final version of the typefaces, as shown in this document, evolved from these studies. Field reviews of the final versions indicate that Clearview should result in a greater than 20 percent gain in legibility and recognition distance in each weight at the same capital letter height as Standard Highway Alphabets, while minimizing halation.

The following section describes the research and the evolution of the Clearview typeface design that has culminated in this interim adoption. As research is completed, legibility and recognition indices (reading distance as a function of capital letter height) will be incorporated into this supplement.

Design Development

In the preliminary research plan, it was assumed that the comparison typeface would be an existing sans serif typeface based on a European example. Though many clearly proportioned typefaces were reviewed - Syntax, Avenir, Thesis, Frutiger, British Transport, Normschrift, Univers, etc. - none provided an acceptable comparison to the standard highway fonts based on stroke, letter width, open shape of counters, and neutrality in character. A simple looking typeface was desired, but one with character and a subtle differentiation between letters to aid word recognition.

Based on these requirements, the project team began by designing two mixed case typefaces that were similar in weight to Series D and Series E-modified. The letter designs were prepared using a series of proportional templates that were not based on other typefaces, but included attributes to aid viewing from long distances. To minimize halation, special emphasis was given to the design of the most critical lowercase letters "a, e, and s," the design of the counters (interior shapes of letters), the relationship of ascender to the lowercase "x," and the geometry of the stroke convergence. The resulting designs were two typefaces: Clearview-Bold (a full width version) and Clearview-Condensed (a narrower version).

The experimental design plan included legibility and recognition tests to accommodate both the known and unknown components of guide sign legends. Legibility is the point at which a viewer can read an unknown legend by identifying each individual letter and building the word. The recognition process is the marriage of the viewer's mental picture of a destination name and the physical word on the sign. For guide signs or street name signs, recognition is often more important because a viewer is looking for a specific name. Research has shown that recognition distance with mixed case legends is twice the legibility distance.

After an experimental design was developed by the research team, subjects viewed actual sign panels on the PTI test track. These studies, in which half of the subjects were older drivers, used real words with three distinct patterns of ascenders and descenders, and with the necessary complexity to test a viewer's ability to recognize word patterns using both Clearview and FHWA Standard Alphabets. Viewers were asked to read signs from a car moving slowly toward the panels in the legibility studies, or were asked to identify the position of a target word on a panel containing three words to test for recognition.

Results of Research & Evolution of the Design

In two PTI studies of conventional road guide signs (Figure 4), use of an early version of Clearview-Bold (left position) improved nighttime sign reading distance by up to 16 percent when compared with E-modified (right position). For drivers traveling at 45 mph, that legibility enhancement could easily translate into 80 extra feet of reading distance, or a substantial 1.2 seconds of additional reading time. On a road with a posted speed limit of 45 mph, a driver is traveling at 66 feet per second. With Clearview-Bold, the desired destination legend is recognized 1.3 seconds earlier (84 feet) and with greater accuracy, giving the driver significantly more time to react to the information displayed.

Figure 4. Clearview-Bold (left) vs FHWA Standard Alphabets Series E-modified (right)

The research (Figure 5) revealed that when the mixed case Clearview-Condensed (upper position) is compared to the most commonly used all-capital-letter typeface (FHWA Series D, lower position), there was a 14 percent increase in recognition distance when viewed by older drivers at night, with no loss of legibility. When the size of Clearview-Condensed was increased by 12 percent to equal the overall footprint of the uppercase display, the recognition gain doubled to 29 percent with little change in overall sign size. By allowing a viewer to read the unique footprint of the word when displayed in mixed case letters, there is an increase in accuracy, viewing distance, and a reduction in reaction time.

Figure 5. Clearview-Condensed (upper) vs FHWA Standard Alphabets Series D (lower)

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