An Evidence Based Model Sign Code - College of Design ...

• Road characteristics. For signs intended to be viewed
from a moving vehicle, the road speed and number of
lanes affect the reading time, viewing distance, and
required maneuver.
Other on-premise sign elements which could be in a model
sign ordinance could include:
• Sign type. There are many types of signs including
monument, pole, wall, projecting, roof, etc.
• Maximum sign size and maximum content size. From
a technical perspective, the larger a sign or the content is,
the more visible it becomes. The authors recognize that
a local jurisdiction may want to establish a maximum size
for signs and/or sign content. However, doing so is a
policy issue and beyond the scope of a technical review.
• Relation to other signs. The amount of information
present in the visual field has an impact on the search
and identify abilities of drivers. In an environment with
a large number of brightly lit signs, a driver will have
more difficulty identifying a particular sign. However,
establishing limits on the number of signs that can be
placed in an area presents legal issues that are beyond
the technical issues of conspicuity and legibility.
• Typeface issues. It is not possible to restrict typefaces to
only those that are approved by a jurisdiction. Furthermore,
the purpose of the ordinance should not be to
define sign design to the level of detail that determines
whether a sign is effective. The business owner and sign
fabricator have a responsibility to design a sign that is as
effective as possible with the general constraints established
by the sign ordinance. In addition to the typeface,
the model ordinance will not address letter spacing or
the amount of white space that a sign is required to have.
• Letter height as a function of Viewer Reaction Distance
(VRD) and Legibility Index (LI).
• Sign size as a function of copy area.
• Sign height as a function of blocked sight distance.
The USSC document does not distinguish between different
types of signs, such as wall signs, ground signs, roof signs, or
projecting signs. Nor does the best practices document
present the information in tables that would be simple to
apply to a variety of conditions. The USSC best practice
document indicates that the sign recommendations are
based on a series of USSC research reports prepared by the
Pennsylvania Transportation Institute. In defining the best
practices, the document does not indicate the specific research
results that the recommendations are based upon.
Using a combination of the recommendations contained in
the Urban Design Associates technical report and the USSC
best practices guide, the team recommends the following
guidelines for developing minimum dimensions for letter
height and overall sign size.
BASIS FOR CALCULATING LETTER HEIGHT
The minimum letter height required for sign legibility is a
function of the distance at which the sign must be read. In
turn, this distance is a function of the amount of content in
the sign, the speed of the vehicle as the driver reads the sign,
and the legibility index of the sign copy. Equation 3 presents
the basic formula for calculating letter height. Figure 9 illustrates
the application of the formula to a road situation.
Determining Letter Height and Sign Size
for On Premise Signs
The minimum sign size charts are based on several research
studies and findings conducted by the Pennsylvania State
University. The PSU recommendations are contained in a
document entitled “On Premise Signs: United States Sign
Council Best Practices Standards. A Research Based Approach to
Sign Size, Sign Legibility, Sign Height” (Bertucci, et. al 2003).
This document contains guidelines for calculating the
following on-premise sign factors:
Equation 3
A Legal and Technical Exploration of On-Premise Sign Regulation: An Evidence Based-Model Sign Code 25