SIGN DESIGN TO MEET CONSUMER
NEEDS AND PREFERENCES
Alison Smiley PhD CCPE is President of Human Factors
North Inc., a Toronto based consulting firm founded in
1982. With a team of 6 specialists, with backgrounds in
engineering, psychology and kinesiology, Human Factors
North provides the full range of ergonomics expertise. Our
goals are to increase comfort, reduce errors and accidents
and improve efficiency in interactions between humans
and their equipment and workplaces. We consult on a wide
variety of issues including: wayfinding and sign
design, traffic accident analysis, fatigue and shiftwork,
marine human factors, and office and industrial
ergonomics.
Alison Smiley, PhD, CCPE
Human Factors North Inc.
Page 1
SIGN DESIGN TO MEET CONSUMER NEEDS AND PREFERENCES
Alison Smiley, PhD, CCPE
Human Factors North Inc.
To design signs according to consumer needs and preferences, there are two issues to
be considered. The first issue concerns the fundamental level of usability. Consumers,
who have only a few seconds to allocate to a sign when they are driving, prefer signs
that can be located easily, read quickly, use pictographs that are understandable and
contain the information they need. In order to meet these demanding requirements, sign
design must be based on scientific knowledge of driver vision, visual search patterns,
information processing rate and manoeuvre times (e.g. time to change lanes at 100
km/h). Usability is addressed through knowledge of human factors.
Once the usability requirement is met, then and only then should the second issue of
consumer preference be dealt with. This concerns aesthetic response and matters of
taste – such issues are best dealt with in focus groups or through market testing. In
these settings consumers can spend time comparing different designs and select the
most aesthetically pleasing ones. The only designs presented should be those that we
know in advance will be useable and effective on the road. The reason for this is that
when consumers have unlimited time to read signs, they may well prefer different, more
complex and ornate designs, than when they are driving by at 20 – 30 metres per
second and have only 2 to 3 seconds to spend reading the sign.
To be effective, traffic signs must do the following:
1. Attract the driver’s attention, even in a cluttered background.
2. Maximize legibility through use of optimum letter fonts, line spacing, and colour
contrast.
3. Limit the amount of information so drivers will have sufficient time to read the
entire message, and extract the necessary information.
4. Use letter heights of sufficient size, placed at an appropriate distance from the
turning point, so that drivers have the time to read the entire sign and comfortably
make a lane change, before reaching a turning point.
5. Use pictographs which have been tested for comprehension and have been
shown to be understood by the majority of road users.
6. Limit the use of colour codes to a small set that is meaningful to the majority of
drivers.
Alison Smiley, PhD, CCPE
Human Factors North Inc.
Page 2
1. Attracting Driver Attention
Tourist signs need to be located so that they are clearly visible to roadway users. This
means that they should be located within the driver’s line of sight, preferably on the right
hand side of the road, where drivers expect to find signs. In a cluttered background,
signs need to use colours that contrast with the background against which they are
seen. Borders assist in making signs conspicuous.
At highway speeds, drivers are travelling along the road at rates of 20 – 30 metres every
second. Therefore, they usually have only a few seconds to locate and read signs.
Precious seconds can be wasted if drivers have to read every sign to find the information
they want. Tourist signs that have a consistent appearance (e.g. in background colour,
number of lines, placement of pictographs, etc.) will be spotted more readily by drivers.
2. Maximizing Legibility
Once a driver locates a sign, he or she must read it. The distance at which text can be
read, or its legibility, is determined by:




letter height
font type
use of upper/lower case
line spacing
Letter height:
One of the key factors in ensuring sign legibility at the required distance is the letter
height. However, legibility distance for a given letter height also depends on the font.
Font type:
Font determines the appearance and shape of the letters. Short, fat letters have better
legibility than tall, thinner letters. Legibility is best for fonts which are simple, rather than
ornate. Recently, a new font called Clearview was developed for traffic signs. It has been
shown to be significantly more legible at night than even the Series E(M) font, which is
currently being used in Canada and the U.S. on highway guide signs. Because of the
increased openness of Clearview characters, words in Clearview font take up 12% less
sign space than words in Series E(M) font, but provide exactly the same legibility. This
font is being used on tourist signs in Pennsylvania.
For the purposes of determining letter height, the legibility of E(m) and Clearview fonts
should be assumed to be approximately 4.8 m/cm of letter height. In other words, a 20
cm letter can be read by most people at a distance of 96 m. This may seem long, but for
a driver traveling at 80 km/h this allows less than 5 seconds. During this reading time,
drivers have to continue to watch the road, and can only devote a portion of the available
time to reading the sign. Furthermore, an Ontario study showed that the majority of the
time that drivers are using signs to go to tourist destinations, they are not assisted by a
passenger (Smiley et al., 1996). Therefore, it is important that letter heights be of
sufficient size to allow a driver adequate time, on their own, to obtain information from
the sign.
Alison Smiley, PhD, CCPE
Human Factors North Inc.
Page 3
Upper/lower case:
In terms of legibility, mixed case text is better than upper case text, as long as the
maximum height of the lower case letters is the same as the height of the upper case
capitals. Words in mixed case are easier to recognize at a distance since each word
forms a distinctive shape with a unique pattern of ascenders, descenders, dots and other
features. Word shape pattern recognition enables the driver to identify a word before it
can actually be read.
Line spacing:
The spacing between lines of text on a sign should be sufficient so that the individual
lines are distinguishable from a distance and the message can be clearly read. The
general guideline is to provide a space of between 0.5 to 1 times the maximum letter
height between each line and the legend centred vertically on the sign blank.
Background colour contrast:
The colour contrast between the background and text influences the legibility of the sign.
High contrast between letters and background (e.g. white text on blue background) will
allow letters to be read at a greater distance than is possible with low contrast colour
combinations (e.g. orange text on blue background). Based on the reflectance properties
of MUTCD colours it is possible to calculate the contrast percentage of colour
combinations. For example, white text on blue background has a contrast ratio of 91%
whereas orange text on blue background has contrast ratio of 42%. A minimum of 50%
contrast is recommended (Dudek and Huchingson, 1986).
3. Limiting Amount of Information Displayed
While dividing their attention between sign reading and driving, studies show that drivers
require about 1/2 second to 1 second to read each word, number, or pictograph. The
smaller the letter height, the less time is available for drivers to read signs. A driver’s
view can be blocked for a second or two by a larger vehicle such as a van in front.
Furthermore, a driver may be required to respond to manoeuvres made by other drivers
at the very moment that the sign is legible. To allow drivers some leeway when looking
at the sign, the absolute minimum letter height for any road sign is 10 cm. This allows
only 3.5 seconds at 50 km/h and less at higher speeds.
A study for the Ministry of Transportation in Ontario determined that, using 19 cm letter
heights, on highways with an 80 km/h speed limit, that 3 two-line place names together
with distance and direction was the maximum drivers could read in the time available
(Smiley et al., 1996). When drivers read signs with 4 or 5 names, they frequently made
mistakes in reading the direction for their destination. Based on this study, tourist signs
with 3 names and 19 cm letter heights were implemented.
When only pictographs or logos are displayed, a single sign should be limited to 6 at
most. When more pictographs are used, the MTO study found that drivers made errors
in obtaining information from the sign.
Alison Smiley, PhD, CCPE
Human Factors North Inc.
Page 4
4. Determining Required Legibility and Placement
A number of factors must be considered to ensure guide signs are legible at an appropriate
distance.
The sign letter height must be large enough to allow the driver time to read the whole
message and, if necessary, time to make a lane change before reaching the turn point.
Figure 1 shows how placement distance and legibility distance affect the distances
available for reading and manoeuvring.
Figure 1:
Distances for Letter Height Calculation
Placement
Distance
Manoeuver
Distance
sign
Legibility
Distance
Reading
Distance
The following steps should be used to determine the minimum letter height on a text sign, or
the pictograph size on a pictograph sign, to accommodate the majority of the driving
population:
1. Reading Time: Assuming ½ - 1 second per major word or pictograph, calculate the time
required to read the entire sign message.
2. Manoeuvre Time: Assuming 8 – 10 seconds for a lane change, determine the time to
complete any required manoeuvre.
3. Required Legibility Distance: Convert reading and manoeuvre time to distance by
multiplying by travel speed (e.g. 2 seconds reading time + 8 seconds lane change time =
10 seconds. 10 seconds at 80 km/h is equivalent to 220 metres)
4. Minimum Letter Height: Assume a legibility distance of 4.8 m/cm of letter height. For a
required reading + manoeuvre distance of 220 m. and a placement distance of 0 m.,
letter height = 220 m./4.8 m/cm = 46 cm.
If signs are placed sufficiently in advance of a turning point that no manoeuvre is
required before reaching the sign, then minimum letter heights will be smaller.
Alison Smiley, PhD, CCPE
Human Factors North Inc.
Page 5
5. Legibility of Pictographs
Pictographs can convey in a single image the same message that may require several
words of text. Therefore the pictograph size is generally considerably larger than
individual letters. As long as the smallest critical detail (e.g. the individual grapes on a
winery sign) on a sign is large enough, the sign will be legible at greater distances than
the equivalent word message.
6. Use of Pictographs
Pictographs are often placed on tourist signs next to a destination name to indicate the
type of destination (e.g. campground, marina, etc.). Pictographs are also used on their
own as trailblazers (e.g. on a winery route). In either case, it is important that users
understand their meaning. What may be obvious to the designer, and to others with
insider knowledge, may not be obvious to the general public. Therefore, testing and
redesign, if necessary, is required. How this is done is discussed in the section below.
Although pictographs would appear to be helpful to drivers, an MTO study found that
drivers actually made more errors when reading signs with pictographs than those
without. It seems that the pictographs were additional information that had to be read,
and as such, reduced the time available for each piece of information, and, in turn, the
accuracy with which the sign was read. Furthermore, an Ontario survey of tourists found
that ¾ of those who used signs were looking for a specific destination name, not just a
type of facility.
7. Comprehension of Pictographs
When pictographs for guide signs are developed, they can be tested in a number of
ways. Generally they are shown to a committee who comment on the adequacy of the
design. Several alternative designs may be shown to focus groups to determine driver
preference. They may then be mounted at a test location, and any public feedback
about them is recorded before a final design emerges. However, none of these methods
ensures that a sign will be comprehended by the majority of drivers. Focus groups
reveal preference, which may have to do with attractiveness of a design, but not
necessarily with the ability of individual drivers to comprehend a sign, particularly when it
is viewed very briefly, at a distance, as the driver passes by.
To ensure that the majority of drivers understand the sign it should be tested with a
representative sample of drivers - on the order of 200, with varying age, education and
language backgrounds. If a sign must be produced quickly, there may be insufficient
time for a systematic test. In this case, there are some simple steps that can assist in
developing a sign likely to be understood by the general public. The sign, or signs if
there are alternative designs, must be shown to a sample of the general public. Office
employees within the organization which is developing the signs are not ideal candidates
because of their "inside knowledge". A minimum sample would be 24 drivers, and this
sample should include approximately 1/3 under age 25, 1/3 aged 26 to 55, and 1/3 over
55 years. Less educated rather than better-educated drivers are preferable. When there
are several alternatives of one sign to be tested, it is preferable that each driver be
tested with only one version of the sign.
Alison Smiley, PhD, CCPE
Human Factors North Inc.
Page 6
Sample signs should be drawn up. Each sign should be placed in a background typical
of the context in which it will be seen, e.g. on a freeway, at an urban intersection. Drivers
should see the sign for a few seconds only - this is generally the length of time they have
to figure out a sign on the roadway. Drivers should then be asked simply what the sign
means and their answer recorded. This technique is preferable to using a multiplechoice approach, because it will reveal potential confusions. Where fewer than 80%
(20/25) of drivers tested understand the sign, redesign is required. The drivers' wrong
answers will assist in determining what aspects of the design need to be changed.
Where comprehension is poor, and redesign is required, it is often the case that only
small changes need be made to improve comprehension significantly. After redesign,
the pictograph should be re-tested for comprehension.
8. Use of Colour Codes
Colour coding, used appropriately, speeds up visual search and is an effective way to
assist drivers in locating particular information, However, the choice of colours for
highway signs is severely constrained. First, many colour backgrounds are used as
codes, associated with particular classes of signs: red for stop signs, orange for
construction signs, yellow for warning signs and white for regulatory signs. Second,
large manufacturers (e.g. 3M) only produce a limited number of standard colours.
Special colours are considerably more expensive.
While colour assists visual search, too many colours can defeat the purpose of colour
coding. Colours on a sign should be limited to 3 – 5. Any colour codes used should be
limited to categories that are useful to the driver. For example, each municipality may
want its own colour background. Unless this is useful or meaningful to the driver, colour
codes should not be used in this way. It is particularly important to select colours that
allow drivers to distinguish between standard road signs (generally white on green
backgrounds) and tourist signs (often brown backgrounds, in Ontario, blue
backgrounds). It is also useful to use colour or standardized formats to distinguish
between motorist services (e.g. food, fuel, hospital, police, which are typically
pictographs) and tourist destinations.
Alison Smiley, PhD, CCPE
Human Factors North Inc.
Page 7
Bibliography of Sign Design References
Bhise, V.D. and Rockwell, T.H. Development of a driver-information-acquisition based
operational tool for the evaluation of highway signs. Presented at the 1973 Annual Meeting
of the Highway Research Board, Washington, D.C. 1972
Dudek, C.L. and Huchingson, R.D. Manual on real-time motorist information displays.
Federal Highway Administration report #FHWA-IP-86-16, 1986.
Mace, D.J. and Gabel, R. Model highway visibility, minimum required visibility. Paper
presented at the Transportation Research Board Annual Meeting, Washington, D.C.
January, 1992.
Smiley, A., Courage, C., Smahel, T., and Fitch, G. Driver response to Toronto street
name signs: an on-road study. Prepared for Toronto Transportation, August 1999.
Smiley, A., Dewar, R.E., MacGregor, C.G., Kawaja, K.M., and Blamey, C. Development of
bilingual freeway exit sequence signs. Transportation Research Record, 1456, 11-19,
1994.
Smiley, A., MacGregor, C., Dewar, R.E., and Blamey, C. Evaluation of prototype
highway tourist signs for Ontario. Transportation Research Record, 1628, 34-40. 1998.
Alison Smiley, PhD, CCPE
Human Factors North Inc.
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