4.1.2Case Examples#
Case examples in the use of narrow lanes are presented from observed temporary alignment practices in Germany and of existing narrow lanes in Queensland.
4.1.2.1Queensland – existing permanent road examples#
Most roads across Queensland generally comply with the widths defined in the Austroads guidance, particularly on higher traffic roads. There are, however, examples of high-volume urban roads with lane widths less than 3.0 m as detailed below. These examples appear to support the finding that narrow lane widths can operate satisfactorily for specific circumstances.
| Road | Posted speed (km/h) | Lane width (m) |
|---|---|---|
| Milton Road, Milton, Auchenflower, Toowong | 60 | 2.6 - 2.8 m |
| Ipswich Road, Annerley | 60 | 2.8 m |
| Moggill Road, Toowong | 60 | 2.8 m |
It is also observed there are existing roads in constrained environments, most particularly on sections of the Pacific Motorway, Legacy Way, Clem7 and Airport Link where shoulder widths between lanes and permanent road safety barriers are as narrow as 0.5 m while maintaining a posted speed of 80km/h and it appears to be narrower in constrained sections. Further on bridge structures (eg Captain Cook Bridge, Centenary Highway Bridge, Houghton Highway and Ted Smout Memorial Bridges both 2.7 km in length) barrier offsets as narrow as 0.2 m are also observed for extended bridge lengths while maintaining posted 80 km/h speed limits.
4.1.2.2Germany#
An example of the use of narrow lanes at roadworks was observed on German Autobahns (January 2020). Works on the Autobahn utilised lane widths reduced to approximately 2.6 m while maintaining a 60 km/h speed limit. In these circumstances a three-lane single direction carriageway had been converted into two two-lane carriageways whilst works were being undertaken on the opposing carriageway.
A key mitigating factor applied at these works were signs banning vehicles wider than 2.0 m from the median side lane. It should be noted that the largest vehicles observed on these roads were 19 m semi-trailers.
In this circumstance, the narrow lane widths appeared to result in high levels of compliance with the posted 60 km/h speed limit despite much higher speed limits on the approaches (110 km/h, 130 km/h, unlimited speed).