The Problem
Highway signage (the icons for services as well as the shape and size of exit and off-ramp signs) is not typically designed optimally to accommodate for reading at high speeds and colorblindness.
Texas Highway
My task was to re-imagine how highway icons and exit signs might be more thoughtfully designed with those considerations in mind.
Research
Key Terms
Sign Detectability: likelihood of a sign being found in the driving environment.
Sign Conspicuity: a sign’s capacity to attract a driver’s attention, which depends on sign, environmental, and driver variables 1.
Sign Legibility: how easy it is for an unfamiliar sign’s textual or symbolic content to be read.
Sign Comprehensibility: drivers’ understanding the message. Keeping all of the other terms in mind, sign comprehensibility is the ultimate goal.
Design Considerations
Contrast:
- A large difference between the darkest and lightest portions of a sign is necessary for legibility.
- The standard for federal highway signs, white copy on a green background, only ranks at #8 for legible color combinations 2.
Colorblindness:
- Red-green color blindness: Difficult to distinguish between reds, greens, and oranges. Blues and yellows to stand out 3.
- Blue-yellow color blindness: Altered ability to distinguish some blues from greens and some yellows from violet.
- Total colorblindness: No color, only black and white.
*99% of all color blind people suffer from red/green color blindness, making this the most urgent type to design for 4.
Chromostereopsis:
This is an illusion caused by placing two high contrast colors directly next to each other. Chromostereopsis can cause images to look like they are moving or “fighting” each other, and as a result can be difficult to look at.
Example of the chromostereopsis effect
Driving Speed and Distance:
Speed and distance are important contributors to sign comprehensibility.
Following Penn State’s 10-step guide determines what the sign size should be. For highway signs, the standard is that each letter in a sign must be at least 1 in. tall for every 40-50 ft. of viewing distance.
Legibility is also higher when words use both upper- and lower-case letters rather than all upper-case letters.
Reflectivity at Night:
Specific materials and/or lights must be used to ensure that signs maintain brightness and visibility at night.
- 50% of crashes occur in dark conditions.
- The nighttime crash rate is nearly three times that of daytime 5.
Icon Design
These are the universal icons used to indicate what type of service will be offered at the next exit, such as restaurants, gas stations and lodging.
Example of some of the service icons in use today
My Redesigns
Three variations per sign show the iterative process, with last photo (right) being the final iteration.
- All designs use a yellow and black color palette, the best palette for sign visibility
- Symbols + text are included in each icon – using multiple methods to ensure the message gets across
- A mix of lowercase and uppercase letters is used to increase sign legibility
- Bold, heavy typeface “Corbel” with thick lines is used for visibility and accessibility
- Emphasis on contrast over meanings of colors to make the signs accessible to all types of colorblindness
Color Palette based on #1 Most Visible Colors for Drivers
Exit Signs
These are the signs that indicate where you can access a specific service such as restaurants, gas stations and lodging.
Exit signs in use today
My Redesigns
- “LoneStar Logos” blue is incorporated in all exit sign designs for recognizability because that is the standard color used Specific Service Signs in Texas.
- White and/or black outlines are used in between all bright colors to avoid chromostereopsis effects
- Exit numbers on the right hand side shows drivers that exits are located on the right
Color Palette based on Standard Highway Sign Colors for Recognizability
First iteration of the “lunch tray” idea with a common plate and utensils layout
Shapes modified to look more like a lunch tray, utensils to symbolize food
Exit # moved to bottom right for higher visibility based on reading patterns
Hamburger shape to try something more creative and fun, with restaurants in the middle to symbolize food
Off-Ramp/Directional Signs
These are the signs you see when you take an exit and need directions on where to turn next.
Directional off-ramp signs in use today
My Redesigns
Color Palette based on Standard Highway Sign Colors for Recognizability
Inspired by fun directional signs at tourist attractions, these arrow shapes immediately show which direction to drive for each restaurant
- This iteration is a consolidated and simplified version of the first arrows sign, designed for quick comprehension
- Changes include generalized distances and “need to know” information only
Design Choices
Contrast > Color
All of the designs focus on high-contrast signage that are distinguishable in both color and gray scale, accommodating for color blindness
Lettering
Using the formulas with a driver going 70mph ( the average highway speed limit in Texas), the letter height for 10 letters is the minimum of ~12″.
A mixture of upper-case and lower-case letters rather than all upper-case is used on all signs because it is proven to be better for legibility.
To keep the design language consistent, all icon signs were created within the largest (10 letters) size even though the words with less letters are still visible at a smaller size.
Consistent Elements:
- Bright, contrasting colors
- Thick, clear lines
- Use of both icons and words so multiple methods of communication are being addressed
Future Considerations
Although black text with a yellow background is the most effective for sign visibility, the color combo is normally used for urgent signs
To avoid confusion, another high-contrast color combo may be used:
With white/black outlines in between colors to avoid chromostereopsis.
If produced, all of these signs should be made with reflective materials or have lights that highlight the designs at night for visibility.
Depending on the speed limits, letter height, size and spacing may change for each region’s highway signage. However for consistency, highway officials may choose to design all signage across the country for the highest speed limits to avoid confusing drivers.
If given more time to pursue this project, user testing would be conducted to test the viability of these sign designs, including interviews and observing behavior. Users would include people of all ages, gender and ability to ensure that highway signs are accessible to all drivers.
Sources
1. Highway Sign Visibility: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.452.7608&rep=rep1&type=pdf
2. How Big Should Sign Letters Be?: https://fasi.org/2016/04/20/how-big-should-a-signs-letters-be/
3. Designing Signs for Colorblind Viewers: https://michigansignshops.com/blog/signs-for-colorblind-viewers/
4. Colorblind Friendly Palettes: https://venngage.com/blog/color-blind-friendly-palette/
5. Minimum Retroreflectivity: https://safety.fhwa.dot.gov/roadway_dept/night_visib/policy_guide/sign_15mins/
