Ontario traffic manual

1. Introduction
Book 6 (Warning Signs) is one of a series of volumes
that makes up the Ontario Traffic Manual (OTM).
Book 6 addresses the selection and application of
warning signs. It should be read in conjunction with
Book 1 (Introduction to the Ontario Traffic Manual)
and its appendices, which contain considerable
essential information about the fundamental
principles and policies behind the design and
application of traffic control signs, signals, markings
and delineation devices.
Book 6 is not intended to provide sufficient detailed
information to allow the design, fabrication and
installation of individual signs. For these purposes,
reference should be made to Book 1b (Sign Design
Principles), Book 2 (Sign Patterns and Fabrication)
and Book 3 (Sign Support and Installation).
Other books in the OTM series provide practical
guidance on a full range of traffic control devices and
their application. A complete listing of the planned
and currently available volumes, as well as the tables
of contents for all books are found in Book 1, and an
illustrated master index, is found in Book 1a
(Illustrated Sign and Signal Display Index).
1.1 Application of Warning Signs
Warning signs are intended to provide advance notice
to road users about unexpected and potentially
dangerous conditions on or near the road. The
conditions to which warning signs apply typically
require that road users exercise caution, and may
require that drivers slow down, in order to travel safely
in the presence of a hazard.
Book 6 Warning Signs
In order to retain the public credibility of all traffic
control devices, consistency in application is
necessary. Insufficient warning signing may leave
road users unprepared for encountering hazards, while
over-signing or exaggerated signing may result in
complacency. It is important, therefore, that warning
signs accurately convey the severity of the hazard
about which they are warning.
The type of warning signing used and the sign size
are impacted by the classification of highway or road
to which the signs apply. For determining sign type,
road classifications used in the OTM are shown in
Figure 1 and defined in Appendix A (Definitions). For
determining sign size, the following three speed
ranges have been adopted:
(1) Speed limits of 60 km/h or lower;
(2) Speed limits of 70 or 80 km/h;
(3) Speed limits of 90 km/h or higher.
Where various sign sizes are shown in the OTM, the
base or standard sign size is recommended as the
minimum sign size. It is typically the sign size that
will apply for the lowest speed range. Where specific
sign sizes are recommended for the other speed
ranges, they should also be regarded as minimum
sizes for those speeds. For some sign designs, only
one or two sign sizes are shown. In this case, two or
more of the three speed ranges are combined
into one.
Where, in the traffic practitioner’s judgement, it is felt
that the recommended minimum size is too small,
and/or greater emphasis is needed, a larger sign size
should be used. More information on sign size is
provided in Book 1b (Sign Design Principles).
Ontario Traffic Manual July 2001 11