Each rural two-lane state highway has been broken up into road sections. Each road section strategy caters to a particular range of projected traffic volumes and downstream road gradient.
Depending on traffic and road conditions, one of four different strategies would be applied to each section of state highway. The interim (10-year) strategy may differ from the long-term (30-year) strategy for each rural two-lane state highway section. The four strategies are:
mixed passing and overtaking
For large parts of the rural state highway network with less than 4000 vehicles per day (vpd), overtaking or mainly overtaking strategies should be viable.
On some road sections, it may be possible to operate an overtaking strategy up to about 7000 vpd, where sight distance is still adequate, as shown in the photo below on the left (SH1 south of Mataura).
Mainly overtaking strategies would generally involve an overtaking strategy with a few low-volume passing treatments, such as slow vehicle bays and marked wide shoulders at selected locations. Slow vehicles bays, as shown in the right hand photograph below (SH10 Kaingaroa), help to address localised deficiencies in sight distance.
For road sections with projected 4000–10,000 vpd, more passing lanes would be required on sections with inadequate sight distance. On road sections with longer 10–12km spacings between passing lanes and to a lesser extent 4-6km spacings, motorists might do some overtaking to help reduce passing demand between passing lanes, as shown in the two photographs below.
The 10,000–25,000 vpd interval is typically above the range for efficient use of passing lanes in series on flat and rolling road gradients but four-laning may not be cost-effective.
An intermediate step needs to be considered between passing lanes in series and four-laning. The Transport Agency is currently investigating the suitability of 2+1 lanes (ie continuous alternating passing lanes) as shown in the photograph below.
*Not strictly 2+1 lanes but the layout shown in the photo is expected to be similar to 2+1 lanes.