APPENDIX E – A BRIEF INTERNATIONAL REVIEW OF THE
SIGNING OF LANDSLIDE AND OTHER HAZARDS
by M G Winter
In this appendix a brief and selective review of the approach to
the signing of landslide hazards in a road environment in both the
E.1 UNITED KINGDOM
Figure E.1 illustrates the sign typically used to indicate
rockfall in the United Kingdom.
Figure E.1 – UK rockfall sign (a) indicating risk of
falling or fallen rocks (TSRGD, 2002: Diagram 559) and (b)
sub-plate to show distance over which the hazard extends (TSRGD,
2002: Diagram 570).
Item 4 (Figure E.1a) indicates that the symbol may be reversed
if appropriate and Item 5 that if the sign is not illuminated then
it must be reflectorised.
A sub-plate may be added to the main sign in the UK to indicate
the distance over which the hazard is extant. Item 4 (Figure E.1b)
indicates the manner in which the distance may be expressed, while
Item 5 indicated that illumination/reflectance should be the same
as for the main sign.
E.2 NEW ZEALAND
In New Zealand ‘international’ graphics are used on
signs, although the warning symbol is placed on a diamond rather
than the more usual triangle. Signs with a yellow background are
used for permanent signs and signs with an orange background for
temporary hazards (Figure E.2):
A sub-plate indicating ‘Caution Slip’ or ‘Caution
Washout’ is often used indicating that the signs are often
used to indicate landslides in a more general sense than simply
rockfall (G Pinches, Personal Communication, 2007).
Figure E.2 – New Zealand sign warning of a temporary
Figure E.3 illustrates an alternative approach to signing
rockfall hazards in New Zealand.
Figure E.3 – New Zealand sign warning of a temporary
landslide hazard. (Photograph courtesy of Thomas Glade.)
In Greece the sign illustrated in Figure E.4 is used for
rockfalls. It is understood that landslides are not generally
signed in any systematic fashion (P Marinos, Personal
Figure E.4 – Greek sign warning of a rockfall
In British Columbia in Canada signs are standardized in a
These include a Slide Area/End Slide Area (Figure E.5a and
E.5b). While this is not overly descriptive it appears to be
intended to decrease the time spent by motorists in the
section of concern, and therefore intending to reduce the temporal
probability factor of the hazard equation.
There is also a rockfall sign (Figure E.5c), similar to the one
used in the UK (Figure E.1a), however this is stated to indicate
‘watch for rock on road ahead’. Other signs in use
include ‘road subject to flooding’ (Figure E.5d) to
which a sub-plate indicating the distance over which the hazard is
extant may be added (K Turner, Personal Communication, 2007).
Figure E.5 – Landslide and other warning signs used in
British Columbia in Canada: sign indicating the beginning (a) and
end (b) of a slide area; (c) indicating ‘watch for rock on
road ahead’; and (d) road subject to flooding.
Other signs in use in British Columbia include warning signs for
stream-based debris flows (Figure E.6). More general hazard
information signs (Figure E.7) are located in lay-bys which
indicate areas in, and routes on, which hazards might be
encountered whilst and also give information on the nature and
background to the hazards. Both types of sign, in addition to
providing information on the type and location of the hazard give
advice on what not to do in the hazard areas.
Figure E.6 – Sign indicating stream-based debris flow
hazard on the Vancouver to Whistler, Sea-to-Sky Highway in British
Columbia in Canada.
Figure E.7 – Landslide hazard information sign on the
Vancouver to Whistler, Sea-to-Sky Highway in British Columbia in
E.5 HONG KONG SAR
In Hong Kong essentially the same sign is used for rockfall
hazards as in the UK (Figure E.8).
Figure E.8 – Rockfall road sign in Hong Kong.
(Photograph courtesy of Thomas Glade.)
Figure E.9 illustrates the symbol used to warn of landslips in
Hong Kong as part of the warning system described in Appendix G.
The symbol is used in the media and on the internet as well as on
public warning signs (Chan and Mak, 2007).
Figure E.9 – Landslip warning sign in Hong Kong (from
Chan and Mak, 2007).
A variety of other signs are used in relation to landslide
hazards in Hong Kong, including those forming part of the slope
registration system and general information signs intended to give
warning of landslide risk to residents and pedestrians. Of perhaps
most interest in the context of roads is the use of the same symbol
sign as that illustrated in Figure E.8 to indicate not only the
start of a landslide hazard, but also the distance over which the
hazard is extant (Figure E.10) and the end of the hazard area
Figure E.10– Rockfall road sign in Hong Kong indicating
the start of the hazard and the distance over which it is
Figure E.11 – Rockfall road sign in Hong Kong
indicating the end of the hazard.
In Croatia the same sign is used for rockfall hazards as in the
UK (Figure E.12) with the use of a distance sub-plate also being a
common factor albeit that the distance is quoted in metres rather
than in miles and/or yards.
Figure E.12 – Rockfall sign in Croatia.
E.7 UNITED STATES OF AMERICA
A wide variety of signing for landslides may be encountered in
the United States of America (USA). These include signs dealing
with quite specific types of landslide hazard (Figure E.13).
Figure E.13 – Rock avalanche sign Lassen Volcanic
National Park. (Photograph courtesy of T Glade.)
More typically the signs indicate a particular type of hazard,
often with an indication of the distance over which the hazard is
extant (Figure E.14 and E.15).
Figure E.14 – Rockfall sign Palo Duro Canyon State
Figure E.15 – Rockfall hazards associated with the sign
illustrated in Figure E.14, Palo Duro Canyon State Park,
Other hazards are often signed in a similar fashion. For
example, hazards associated with streams that become active during
and after heavy rainfall are sign as illustrated in Figures E.16
and E.17. In this case a maximum speed limit is imposed.
Figure E.16 – Water hazard sign Palo Duro Canyon State
Figure E.17 – Water hazard associated with the sign
illustrated in Figure E.16, Palo Duro Canyon State Park,
Such signs are not restricted to relatively lightly trafficked
park roads but are also used on heavily trafficked interstate
highways. Figures E.18 to E.120 illustrate
Figure E.18 – Water hazard sign Interstate 28, Hale
Figure E.19 – Water hazard sign Interstate 28, Hale
Figure E.20 – Water hazard associated with the signs
illustrated in Figures E.18 and E.19, Interstate 28, Hale County,
Similarly, less effective signing in relation to hazards may be
encountered in the USA. Figure E.21 shows a sign for a
‘Tornado Shelter’ – the relevant text is in black
on a white sub-plate below the large blue sign to the right of the
picture. The large blue sign promotes the rest area which includes
the tornado shelter (Figure E.22
Figure E.21– Sign for ‘Tornado Shelter’ at
a rest area Interstate 28, Hale County, Texas. The white
‘Tornado Shelter’ sign is on a white background and is
located below the blue ‘Rest Area Next Right’ sign to
the right of the picture.
Figure E.22– The rest area associated with the sign
illustrated in Figure E.19, showing the building containing the
‘Tornado Shelter’, Interstate 28, Hale County,