In 2014 NICTA, at Infrastructure NSW's request, investigated the smart motorway concept on Sydney's M4, with cooperation from the NSW RMS. The purpose was to evaluate the performance of ramp metering, the centrepiece of smart motorway concept, in managing traffic of the selected sections on the M4.
NICTA developed its own ramp metering system and a traffic data analytic tool. The NICTA ramp metering system coordinates ramp signals along the entire smart motorway section in order to optimize control performance. The traffic data analytic tool uses motorway detector data and SCATS data to estimate the origin-destination matrix. The microscopic simulation engine PARAMICS is used for the evaluation.
The historical traffic data suggests that, apart from the M4 sections under the WestConnex project, the section Westbound between Cumberland Hwy and Roper Road is subject to recurrent congestion during the evening peak hours. Subsequent base model development and validation ensured that the recurrent congestion pattern is replicated in the simulation. The key findings from the evaluation include:
- Travel time reduction. The travel time during the most congested period for trips going west along the M4 mainline from Prospect to Roper Rd is reduced from 16 minutes to 9 minutes, registering a benefit of more than 40% in travel time.
- Capacity improvements. On the most congested part of the M4, we can get an additional 1000 cars an hours through the system smoothly. This is up to the equivalent of an extra physical lane provided with smart software.
- Economic impact. Over a year, the M4 can save 400,000 hours a year - that's the same as 300 people working for a year. The direct economic cost about $22m a year, no taking account of additional social and environmental cost.