Signage Readability

Signage Readability

Signage Design: Less an art – more of a science

What sets apart an ordinary sign vs. an impactful legible sign?
Do most signs “speak” effectively to all viewers?

Signs can only communicate effectively if they are impactful, attractive to the human eye and are readable to everyone.

To effectively convey information to another, one has to possess important ability speak clearly and be able to listen. This similar principle applies to successful functioning, signage which has to be designed with concise images and text to successfully deliver “eye communication to the viewer. I like to call it sign language.

When one understands what factors cause certain SIGNAGE TO FAIL, then one can avoid the payment pitfalls for poorly designed signs.

I don’t judge others, but I sure do judge signage!  As a professional sign designer, no matter where I am, i.e. at an airport, traveling on the road, on a roof or in a hospital – I entertain myself by critiquing signs.

Improperly designed (directional) signage and lack of wayfinding signage, especially on wilderness trails, bicycle routes, park walkways, public boardwalks, tourist attractions, etc., can be dangerous and raise various liability issues for corporations, municipalities, businesses, Government responsible for making their signs.

The most important (life-saving) sign I have personally encountered and have been grateful for was, when I was canoeing down a 200 km wilderness trip on the Missinaibi river to James Bay. After 12 days of paddling with no SIGNS of civilization (pardon the pun ) except for the planes in the sky – suddenly a 16 foot billboard appeared and I read “CAUTION THUNDERHOUSE FALLS”. This particular sign was constructed and implemented AFTER 30 controversial deaths happened at this very dangerous landmark! Most of these “avoidable” deaths were paddlers visiting from other countries enjoying our breathtaking Canadian wilderness. These poor souls were canoeing over the falls to their unexpected deaths due to improper wayfinding signage and portage routes.

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With the revised canoe book maps handmade by Hap Wilson and additional construction of monstrous signage, it is now safe to paddle down the Missinaibi River ( that’s if you can handle Class 3 rapids and transport food without dumping it out of the canoe!)

The most common pitfalls affecting successful signage which I have learned about are:

  1. No signage
  2. Too many signs in a concentrated area
  3. Too much text, not enough negative space in the layout
  4. Poor signage design art and “too busy” layout
  5. Poor typography
  6. Obliquity of viewing angle
  7. Not legible from the proper reading distance
  8. Dimensions of logos are disproportional
  9. Color contrast
  10.  Speed of traffic (ie. in a canoe approaching a dangerous waterfall)
  11. Height and set back


  • The average person takes 0.33 sec to recognize a word or image (given you have 20/40 vision and are not dyslexic).
  • The rule of thumb in this professional signage industry is that is takes 3-5 seconds to read a typical sign. Yet, most signs are read from a distance and 9 times out of 10 the viewer is moving in a vehicle (whom is hopefully abiding by the speed limit – another life pitfall I have experienced)
  • The physical limitations to what the viewer is capable of reading at that distance and has only a tiny window of time to do so.
  • Considering today’s fast-paced lifestyle and technology craze, ie where drivers can be distracted by their children in back seats playing noisy iPod games and the parents themselves are talking on hands free (God forbid they aren’t texting ‘cause crotches kill! So I personally believe road signage formula guidelines may have to be adjusted to compensate for all these distractions. Today’s road signage then may ultimately need to be three times as large)
  • The minimum distance at which a sign must become legible is a function of the time it takes to read the sign and the decisions required to comply with the sign is called the perception-reaction or “PIEV “time (Perception, Identification, Emotion, and Volition) and combined with travel speed the resulting distance is known as the “MRLD”“Minimum Required Legibility Distance”.
  • Given the MRLD, the sign’s letter size is back-calculated using an LI or legibility index. The LI is expressed in feet of legibility distance as a function of a letter height in inches. The rule of thumb for the LI is 30, so a sign with MRLD of 570 feet must have 19” letters. The LI is expressed in feet of legibility distance as a function of letter height in inches (ft/in). For example, an LI rule of thumb of 30 means that a sign with an MRLD of 570 feet must have 19-inch letters (570 / 30 = 19”).
  • When designing a sign it is imperative that it reaches the target audience’s eyeballs or the investment is for not, hence legibility is of utmost importance.

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For example:
If a person is driving to go get some ice cream and is abiding by the law driving at 96km/hr (hopefully he/she is not speeding!) and he/she is able to read the 4.2m x 14 m) sign at a rate of 27 meters/second. At three different locations in proximity to the sign, at 137 meters the viewer has only 5 seconds of reading time!
Hence, at location B at 81 meters the viewer has only then 3 seconds of reading time!


48 km/hr 67 meters  20 cm
72 km/hr  100 meters  30 cm 
96 km/hr 134 meters 40 cm

(Readability distances also vary with color but given black text on white, using a legible font)


The human eye is designed to focus in one direction with peripheral vision extended on either side. The sub portion of that zone is the CONE of vision. (a.k.a. visual awareness). It is recommended that outside of the visual cone a sign’s readability is dramatically diminished.

I have personally spent over a decade testing my own CONE of vision and comparing readability of signage at certain distances to ensure these so called formulas developed by these USSID people actually work!

Clients assume sign designers know what they are doing. I have encountered many unhappy people who have invested in huge costly signs such as billboards, they loved their designs with fancy drop shadows and super cool graphics. Yet when their billboard(s) were up the primary message simply could not be read and were not clearly communicable.

So next time your hiring a sign designer and manufacturer, call us: Alberta : 855.885.2883 | Ontario: 705.773.9738

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Thanks for reading!


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