Contract Report Great Western Highway upgrade (Mount Victoria to Lithgow) Winter weather related issues by Adrian Runacres & Paul Hillier for Roads and Traffic Authority (RTA) of New South Wales (NSW) NC74503 – July 2009 Great Western Highway upgrade (Mount Victoria to Lithgow) Winter weather related issues for Roads and Traffic Authority of New South Wales Reviewed Project Leader PP Quality Manager NC74503 – July 2009 GWH upgrade (Mt Victoria to Lithgow) - Winter weather issues Summary The Roads and Traffic Authority (RTA) of New South Wales (NSW) is committed to the upgrade of the Great Western Highway (GWH) between Mount Victoria and Lithgow in the Blue Mountains region of the state. The existing road section has a difficult geometry given the challenging local topography and road safety concerns have historically been expressed. Many of these concerns can be related to the adverse weather conditions experienced in the region, particularly during the winter season. Localised sections of the existing route are prone to frost and ice formation with the potential to create hazardous driving conditions. Fog can also be a concern, both in winter and summer months. In 2008, as part of the preliminary routing and design of the upgrade, the RTA commissioned ARRB Group to apply recognised microclimatological principles together with the undertaking of a desk study and local site visits to identify the microclimatical (weather related) constraints present within a defined study zone. These constraints were considered alongside a number of others, including environmental impact and heritage. This led to four preferred Route Corridors being identified early in 2009 that have since been subject to further technical investigation and community consultation, including a workshop at Mount Victoria on Saturday 13 June 2009. The workshop provided local residents with information regarding the management of adverse weather on road networks from around the world as well as the constraints within the study zone itself. Residents were also able to provide the ARRB Group team with valuable local perspectives on the weather patterns and influences within the study zone. The RTA is seeking to use the findings of, and opinions and recommendations provided by, ARRB Group to minimise the propensity of frost, ice and fog to form Although the Report is on the new route, where such conditions can be reasonably foreseen. Experience believed to be correct at has shown that this can be achieved through, wherever possible, avoiding the time of publication, ARRB Group Ltd, to the locations that are susceptible to ice formation and by choosing route alignments extent lawful, excludes all that minimise the extent of elevated sections and steep slopes. Similarly, road liability for loss (whether formations and structures can be designed such that the likelihood of frost and ice arising under contract, tort, statute or otherwise) formation on the running surfaces is reduced. Where the risks of frost and ice arising from the contents of formation cannot be completely mitigated, road authorities can consider the the Report or from its use. Where such liability cannot adoption of proactive winter maintenance programs and/or the adoption of road be excluded, it is reduced user warning systems. to the full extent lawful. Without limiting the foregoing, people should Sound maintenance practices can also play an important role in reducing the apply their own skill and propensity for frost or ice to form on a road surface, by ensuring that surface judgement when using the information contained in drainage provision is adequate and functioning and that wheelpath rutting does the Report. not lead to standing water on the surface. Additionally, ensuring that water does not run off onto the highway from adjacent land and that roadside vegetation is maintained can also play an important part in keeping a road surface free from frost and ice. ARRB Group has concluded: • There are climatological concerns regarding all of the four modified route corridors proposed, but these concerns are not considered insurmountable, and therefore, all of corridors are considered potentially viable when only climatic constraints are taken into account. GWH upgrade (Mt Victoria to Lithgow) - Winter weather issues • It is essential that a formal weather data collection regime be undertaken during the winter of 2009 to provide additional, highly localised data to further inform the route selection and design process [NB. the data obtained will also be valuable to the RTA’s local Lithgow office in the design and determination of future network maintenance programs and the placement of any future road user warning systems]. • The regime adopted should take the form of a formal thermal mapping exercise to include the study zone and beyond, with coverage being from Mount Boyce in the east to Yetholme in the west. GWH upgrade (Mt Victoria to Lithgow) - Winter weather issues Contents Summary Summary.................................................................................................................... 1 1 Introduction..................................................................................................... 1 1.1 Improvements to the Great Western Highway - Mount Victoria to Lithgow ................................................................................................... 1 1.2 Consideration of ice formation................................................................ 2 2 Method ............................................................................................................. 4 2.1 Specialist advice..................................................................................... 4 2.2 Investigation and consultation ................................................................ 4 3 Ice hazards ...................................................................................................... 6 3.1 Introduction............................................................................................. 6 3.2 ‘Black ice’................................................................................................ 6 3.3 Hoar frost................................................................................................ 6 3.4 Ice prone sites ........................................................................................ 7 3.5 Climate change....................................................................................... 9 4 Data from the study area................................................................................ 11 4.1 Climatic data........................................................................................... 11 4.2 Accident data.......................................................................................... 13 5 Winter maintenance of roads in NSW........................................................... 15 5.1 Current practice in the Lithgow area ...................................................... 15 5.2 Current winter maintenance practice in other RTA regions ................... 16 6 Current alignment of the Great Western Highway between Mount Victoria & Lithgow .............................................................................. 17 6.1 Ice prone sections .................................................................................. 17 6.2 Fog.......................................................................................................... 18 6.3 Wind........................................................................................................ 19 7 Potential new alignments of the Great Western Highway between Mount Victoria & Lithgow .............................................................................. 20 7.1 General observations ............................................................................. 20 7.2 Modified Orange Corridor (including common elements of all corridors) ................................................................................................ 21 7.3 Modified Red Corridor ............................................................................ 24 7.4 Modified Green Corridor......................................................................... 26 7.5 Modified Purple Corridor......................................................................... 27 7.6 Summary ................................................................................................ 29 8 Comments and recommendations concerning the future maintenance of the GWH between Mount Victoria & Lithgow ................... 31 GWH upgrade (Mt Victoria to Lithgow) - Winter weather issues 8.1 Winter maintenance................................................................................ 31 8.2 General maintenance and other issues.................................................. 32 9 Recommendations for further work.............................................................. 33 9.1 Thermal mapping.................................................................................... 33 9.2 Static weather station ............................................................................. 35 9.3 Mobile weather station............................................................................ 36 9.4 Mobile road condition state and/or road surface temperature sensors ................................................................................................... 36 9.5 ‘Spot’ road surface temperature measuring equipment ........................