Table 3 – Value of Dimension D AS 1742.3: A distance expressed in metres, determined in accordance with Clause 4.1.5 and used for positioning of advance signs and related purposes. Table 3 within the Code of Practice takes precedence over table 4.2 in AS 1742.3 Speed of Traffic km/h Dimension ‘D’ m 55 or less 15 56 to 65 45 Greater than 65 Equal to speed of traffic, in Km/h Table 3 – Value of Dimension D Code of Practice

Speed of Traffic AS 1742.3 1.4.16: The speed limit applying at a location or an estimate of the speed of the majority of vehicles in the stream if considered to be significantly different from the speed limit (see Note 2), either above or below. Clause 4.1.5: (a) The speed of traffic (see Clause 1.4.16) shall be taken as either— (i) the speed of traffic in the speed zone immediately preceding the zone in which the advance sign occurs, see Figure 4.2(a); or (ii) if there has been no zone change for at least the preceding 200 m, the speed of traffic at the advance sign, see Figure 4.2(b).

AS 1742.3 – figure 4.2 page 63

Tolerances on sign positioning Distances may be adjusted within the below tolerances if there are items or features (eg intersections, trees etc) that do not allow the specified spacings: (a) Positioning of signs, length of tapers or markings: (i) Minimum, 10% less than the distances or lengths given. (ii) Maximum, 25% more than the distances or lengths given. These tolerances shall not apply where a distance, length or spacing is already given in the text or a figure as a maximum, a minimum or a range. They may need to be exceeded where road features such as intersections or median openings intervene. FIGURE

Speed limit buffer zones (CoP) Approach Speed Works area speed 80 km/h Speed Buffer Required L1 (80 km/h buffer) m L2 (60 km/h Buffer) L3 110 80 No N/A 220 60 Yes 300 160 40 200 90 100 180 70 45 MRWA requires the values in this table to be used whenever temporary speed zones are required, unless site specific hazards are identified and the spacings need to be changed. The objective of this section is to:  Establish a consistent and uniform approach in the placement of temporary speed zones.  Reduce avoidable delay to road users due to excessive and/or unnecessary temporary speed zone lengths.  Encourage better compliance by road users to temporary speed limited areas.  Educate road users by the standardised placement of speed zone signs. Main Roads WA requires the values (listed in Table 2) be used whenever temporary speed zones are required, unless a site specific hazard is identified and a risk assessment determines the need to extend the sign placement. This shall be documented in the risk assessment and response table of the TMP. Table 2 – Placement of temporary speed limit (buffer zone) signs Code of Practice – page 30

110 Km/h to 40 km/h workzone Example – works off the road within 1.2 m of traffic lane. 110 km/h down to 40 km/h zone.

110 km/h to 60 km/h workzone Example – works off the road between 1.2 – 3 m of traffic lane. 110 km/h down to 60 km/h zone.

80 km/h to 40 km/h workzone Example – works off the road within 1.2 m of traffic lane. 80 km/h down to 40 km/h zone.

Risk Management Approach A risk assessment shall always be conducted prior to determining the appropriate spacings of signs and speed zones. This shall take into account: Road geometry Sight distance Road user behaviour (eg compliance to speed limit) Traffic volume