Freeway & Expressway Guide Signs:
Proportion Based Grid System
With the new Interstate Highway System touching every state nationwide, the 1961 edition of the MUTCD had a much different character and focus than the preceding 1948 version. Freeways dominated and the guide signs for the new interstate highway system required a very different design when compared to conventional roadway intersection. Looking back, we realize there was little change in the design, though materials changed significantly.
To this day, guide sign panel layouts for freeway exits and overhead bifurcations in the MUTCD have been based on a complex set of unique dimensions that are not consistent from one primary legend size to another. Simple panels are similar but often not uniform. Complex panels can be a mash-up of inconsistent dimensions as the layout rules are difficult to apply consistently.
Since the use of Clearview 5-W had received Interim Approval (IA-5), we wanted to learn if we could improve the layout along with the typefaces. To begin, we analyzed and photographed hundreds of applications to better understand the inconsistency of the existing freeway guide sign layouts and the visual relationships of graphic elements.
Using a proportion-based layout (below), all elements are sized based on (X) in which (X) is the primary legend. Following analysis, we revised the format based on ten (10) proportional values that are uniformly applicable to freeway guide sign layout. The layout maintains consistency and proportionality- regardless of primary legend size or content.
Proportion based grids build on a consistent set of rules and simple mathematical proportions. The layout may include: cardinal direction, arrows, route shields, symbols, interline space (single line or return line and panel with more than one destination identified); numbers and fractions; lane drop, the surrounding field and borders. All are displayed in the proportioned based layout.
With our focus on older drivers, we attempted to make the secondary legends for lane drop, cardinal direction and EXIT panels easy to see. The layout system allows us to enlarge those elements while uniformly controlling the surrounding space (e.g. more field for signs viewed with low sun behind panel). An example of the new design that keeps proportional relationships uniform while increasing the size of primary graphic elements at .7X of primary legend. The one exception is the lane drop legend which is shown at .8X. Comparative performance testing research of overall concept compared to current practice is recommended.
We think that consistently arranged and sized displays of component signage will aid readability for the older driver and all drivers. This layout system applied to thirty (23 panels shown below) different frequently used freeway and expressway guide sign formats (not including diagrammatic signs) fit within existing layout proportions. Changes in the size of a route shield (2.5X, 3X, etc.) is easily accommodated within the designed layouts. The design provides spacing below the primary legend on pre-built extruded blanks to insure cross-alignments are uniform on side-by-side signs in overhead displays.
Comparison of existing standards with 25 unique dimensions to Proportion-Based Layout with 10 proportional dimensions and a layout that sizes and places graphic elements uniformly to aid reading at a glance.
This “Metropolis” panel is an example of fixed measure layouts (with more than 25 unique dimensions). The panel formatted using the proportion-based grid system has 10 proportional dimensions. Both examples are based on a 20” primary legend size and are panels of similar height. The alternative approach is designed to create a visually integrated panel. The cardinal direction “NORTH” and “EXIT” to identify the exit number are 14” (.7X) on the proportion based panel in lieu of 12” and 10” employed in the current method of layout.
The alternative approach to cardinal direction eliminates the taller initial capital letter based on a Larson Transportation Institute study that compared all: 1) same size uppercase; 2) mixed case with initial capital letter and, 3) the current FHWA standard with the enlarged initial capital letter with small caps. The study found the upper case bold (Clearview 6-W) word shown without enlarged capital letter was the most effective.
3 Common Applications Using Mathematical Relationships
The Clearview 5-W primary legend improves overall legibility and readability of the destination name. Equalization of the size of supporting elements (route shields, arrows, cardinal directions) aids uniformity. This method of layout also applies to exit direction and lane drop panels.
Freeway and Expressway Guide Signs in Universally Applicable Layout
These 23 sign layouts were formatted using same mathematical relationships
Recreational and Cultural Area Interest Signs for Freeways
General Service Signs, Rest Area and other Road Side Service Signs for Freeways
Fractions: Common Format as a Stand-Alone Ligature or with Primary Number
The components of this design concept are adjusted for view on glance. Fractions (above) are displayed as freestanding ligatures with uniform size for numerator and denominator. A fraction builder tool is part of the ClearviewHWY® font software.
This paper was prepared in 2007 as a concept to improve guide sign layout and readability. The authors have not revised or updated the content except for lane drop/exit panel. The authors have recommended laboratory studies using phycho-physical tests to validate the effectiveness of the various changes to secondary legends and glance readability of primary legend.
D. Meeker, M. Pietrucha, P. Garvey., Proportion Based Format System for Freeway & Expressway Guide Signs., Presented at the TRB Annual Meeting. (2008). ASCE Journal of Transportation Engineering. Washington, D.C. (2010).