Steep grades

Steep grades - signage

As stated in Austroads Guide to Road Design Part 6: Roadside Design, Safety and Barriers,

Long steep downgrades can result in drivers of heavy vehicles losing control and it therefore may be desirable to take measures to prevent the occurrence of and limit the consequences of runaway heavy vehicles. Measures aimed at managing errant vehicles on steep descents include:

• alerting drivers of a steep descent on the approach to the downgrade; and
• regulating the use of low enough gear to control the descent of heavy vehicles; and
• providing containment facilities for runaway vehicles.

Detailed information on designing for steep downgrades is provided in:
Austroads Guide to Road Design – Part 6: Roadside Design, Safety and Barriers(external link)

Typical signs for where steep grades occur and their layout are provided in Table 5‑1 and illustrated in Figure 5‑1.

In addition:

• at upgrades in excess of 10%, advance warning should be provided where the length of grade exceeds 100m; and
• where the length of grade exceeds 1,000m, additional warning should be provided.

Table 5‑1: Steep grade signage

Sign code	Example	Description/use
W14-9 Steep grade down – ‘percent’ symbol		Should: be used in advance of downgrades where vehicle speeds are likely to increase to an extent which would make the vehicle difficult to control; and use the nearest percentage, rounded upward. For sign location, see note 1.
W14.10 Steep grade up – ‘percent’ symbol		Should: be installed in advance of upgrades of 10% or more, and generally at least 100m in length; have no signs other than the W12-3.1 supplementary signs that may be attached to the W14.10 sign or its support; and use the nearest percentage, rounded upward. For sign location, see to note 1.
W14-9.2 Trucks use low gear W14-9.4 Use low gear		May be used in conjunction with a W14-9, either on the same post or separately between the W14-9 and the start of the descent. Should be installed with the W14-9 sign.
W12-3.1 Curve sign supplementary – next ‘[distance]’ km		The W12-3.1 sign may be used in conjunction with the W14-9 or W14.10 signs if the downgrade is longer than 1km.

Table 5‑1 note:

1. The sign should be located where approaching drivers have an uninterrupted view of it over a distance of at least 120m in rural areas or at least 60m in urban areas. The sign should be installed in advance of the start of a grade by 90m in rural areas and by 30m in urban areas.
2. The sign should be installed in advance of the steep grade at least the distance shown in the table below.

   Operating speed	Distance
   50km/h	65m
   70km/h	100m
   80km/h	120m
   90km/h	140m
   100km/h	160m

Figure 5‑1: Steep grade signage layout

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