Main Roads does not know the extent of traffic congestion across its road network

Main Roads controls 850 kilometres of the metropolitan road network but has comprehensive traffic congestion information for less than 10 per cent of this network.

Main Roads collects considerable data from across the road network for separate reasons, in different forms, using different measures, although most does not relate to congestion. In part, this is expected, given that congestion has only recently appeared as a significant management issue. Currently, detailed performance information is available for just 78.5 km of the Mitchell/Kwinana/Graham Farmer freeway system (Figure 6).

Having consistent, real time information is key to optimising network performance and informing strategic and operational decision-making. Without this information, there is a heavy reliance on traffic modelling to predict future demand and network capacity constraints, and a risk that major transport decisions will not address traffic congestion effectively. It is also very difficult to demonstrate that projects to improve congestion provide the best use of resources.

While consistent and comprehensive information is the goal, we acknowledge that creating this information is a challenge. However, evaluating performance across the whole network would let Main Roads:

• measure if the road network is operating as planned and designed
• calibrate traffic models
• benchmark performance against agreed service performance levels
• target network improvement
• inform strategic decision-making
• provide better traveller information
• establish priorities, and assess effectiveness and cost-benefits for operations and network expansion.

Seven uncoordinated systems collect data for different operational and planning purposes across the agency

Main Roads uses seven data collection systems for different operational and planning purposes across the agency. The systems measure different traffic metrics across different parts of the road network and are managed by different divisions. However, only data from the Vehicle Detection System (VDS) is used to monitor traffic congestion and is regularly reported to Main Roads executive.

Two directorates within Main Roads manage the seven systems:

• Road Network Services use:
  • VDS to measure real time network performance and provide planning information. There are 1 600 sensors at 140 points on the freeways system collecting real-time data
  • community perception surveys and customer complaint information to measure performance and inform the management of traffic congestion
  • the Traffic Operations Centre (TOC) to monitor and manage operations of the Perth metropolitan road network. TOC is the central point for real-time traffic information across the State. It uses intelligent transport system devices such as variable message signs and closed circuit television cameras (CCTV) to ensure the efficiency of the road network during peak commuter travel times, special events and unplanned incidents, including 273 CCTV cameras and 65 cameras in the Northbridge Tunnel. It also uses the Sydney Coordinated Adaptive Traffic System (SCATS) to manage all 955 traffic signals across the State (885 in metropolitan Perth). SCATS is used operationally to control traffic signals and improve traffic flow and hence resolve congestion issues. It is not used for monitoring and reporting congestion over time
  • Tom Tom Global Positioning System (GPS) to monitor travel times and speed, since Main Roads purchased access in October 2014.

 

• Planning and Technical Services uses:
  • its new ROM24 system to generate traffic flow predictions and to estimate future traffic congestion
  • ‘stop watch tests’ (known as Floating Car Surveys) to measure regular travel time information along 11 routes in the metropolitan area. This is reported to Austroads which publicly reports on the information annually
  • fixed and temporary road counters are also used to count the number of cars across points in the network. This provides an indication of increased demand on the network.

Traffic volumes and speeds from VDS are used to report traffic congestion to Main Roads Corporate Executive every three months. The information is also sent to Austroads. Four National Performance Indicators (NPIs) are reported (travel speed, efficiency, reliability and productivity). However, this information is limited to 78.5km of the Graham Farmer, Kwinana and Mitchell freeways (Figure 6) and focuses exclusively on the daily commute into and out of the CBD. No congestion information is reported for the rest of the road network, or for high value transport modes like buses and freight vehicles. We note that Austroads has not publicly reported on NPIs since 2009.

Main Roads believes that most of Perth’s traffic congestion is recurring rather than incident based and occurs when vehicle use exceeds available road capacity. In particular, the freeway system that runs more than 100km from Joondalup in the north, through the CBD and south to Mandurah, experiences congested conditions daily during the morning and evening peak times. Significant delays occur along vital routes including primary freight routes, high frequency bus routes and control-of-access highways. Perth’s roads are generally free flowing outside peak hours.

In 2011, Main Roads estimated that 17 per cent of freeway congestion results from crashes, but congestion itself is one of many contributing factors. The Perth figure is on the lower end of international experience. Main Roads plans to analyse this data in 2015‑16.

Main Roads does not use the data it has to its full potential or analyse data to provide meaningful consideration of trends and performance. It does not consistently measure or report the volume of cars and freight vehicles on the whole network (this can be measured as ‘vehicle-kilometres’ travelled), vehicle occupancy levels or the percentage of recurrent and non-recurrent congestion. We expected this information to be readily available and reported.

Main Roads and DoT are working to define a performance metric (or suite of metrics) for congestion. Once these are agreed, and a baseline established, targets can be set and performance monitored and reported to DoT and Parliament. Determining what should be achieved will enable Main Roads to measure reliability, which is widely considered one of the key measures of success in managing traffic congestion.

Where possible and cost effective, data should be real or near real time, enable historic trend analysis and measure traffic volumes and free flow and actual journey times for cars, buses and freight vehicles that would provide delay and speed information. We note this is a challenge for all jurisdictions, however a number of transport agencies, including Washington State, London and in Victoria (VicRoads), publish similar information.