Can you discuss the managed motorways concept and how it is being applied in Melbourne?
Lachlan Gray: Managed motorways incorporate intelligent system tools in and alongside urban freeways to manage traffic with the aim of reducing congestion for improved journey times and more reliable and safer journeys. The concept is deployed in jurisdictions in different ways. The Melbourne managed motorways concept—developed in the early 2000's by VicRoads [now the Victoria Department of Transport and Planning] and industry partners—came from the recognition that we can’t build our way out of congestion as Melbourne continues to grow. There was a need to maximize the capacity of the motorway network at all times. The onset traffic flow breakdown and rapid decrease and instability in speed and throughput needed to be avoided.
Whilst ramp metering and other motorway technologies have been deployed in many jurisdictions, they only offered a limited benefit to a motorway corridor; these techniques may delay the onset of a breakdown but not remove it, so they provide limited value over the long term. By considering the corridor in a holistic way, as part of a whole system, it can be managed and controlled to mitigate disruptive events and increase system resilience. Understanding of the corridor begins with continuous real-time data about motorway performance across every lane along the whole length; managed motorways control—through coordinated ramp metering, variable speed limits and lane-use management systems—can stop flow breakdown. This results in positive safety, efficiency and sustainability outcomes and importantly highly reliable journeys for travellers.
The Melbourne Approach requires a range of physical infrastructure—particularly to create space for vehicles on ramps and possible lane allocation around ramps—ITS devices and control systems to support pre-emptive control beyond the motorway. The approach also requires a strong understanding of traffic flow and behavioral science and continual study and optimization, and finally a robust operational framework to ensure the results can be delivered reliably for road operators.
It’s also important to point out that the holistic approach, as outlined in the Victoria managed motorways framework document, includes adopting a Safe System approach [also known as Vision Zero in many parts of the world] to the design and management of motorways to reduce the incidence of severe crashes.
Earlier, you noted variation relative to the application of the managed motorways concept. Can you provide an example?
Lachlan Gray: The Melbourne Approach does have some differences relative to the approach used in other Australian States and globally. For example, the key difference between the Melbourne approach and the UK [United Kingdom] approach, known as smart motorways, is the UK use of speed harmonization to prevent or slow down flow breakdown along with the use of dynamic lane management, including all-lane running where there is no permanent shoulder lane—as key parts of the deployments. All-lane running is rare in Australia. The other fundamental difference is that the UK does not use coordinated ramp metering or signalling—predominantly due to the relatively long distance between intersections and the lack of capacity for queueing vehicles on short, narrow ramps.
What is the aim of the Smart 25 Managed Motorways Pilot Project, and which features of the managed motorways system in Melbourne are being applied in the Denver metropolitan area?
Scott Pitera: The Colorado Department of Transportation [CDOT] was interested in the Melbourne managed motorways system to improve the performance of I-25 in Denver, without adding lanes. The I-25 corridor selected for the SMART 25 Pilot Project underwent a major reconstruction in the early 2000's that added lane capacity and an adjacent light-rail line. Fifteen years later, the freeway was more congested than it ever was before, and CDOT began to explore technology-based solutions to reduce travel times, improve travel time reliability and increase traffic flow without the major expense and community impacts of further freeway expansion.
WSP, in partnership with VicRoads/VicDOT [now the Victoria Department of Transport and Planning] was responsible for introducing this concept to CDOT and conducting the initial regional screening and feasibility study. Through that process, CDOT chose to focus on the coordinated and adaptive ramp metering [CARM] aspects of Australian managed motorways for the SMART 25 pilot. CARM uses sophisticated algorithms and control systems and real-time data from advanced traffic detection systems to adjust the entry of vehicles onto the freeway to minimize the formation of bottlenecks. All the ramps are able to coordinate and work cooperatively to respond to real-time data, minimize flow breakdown and prevent impacts to adjacent arterials.
Performance of the Smart 25 Managed Motorways Pilot Project has demonstrated that the CARM concept can bring multiple benefits:
- Decrease the severity and duration of congested periods (14.3% average decrease in travel time for PM peak traffic period)
- Reduce overall travel times (19% reduction at height of PM peak travel time)
- Increase travel time reliability (average reduction in 95th percentile travel time of 5.4 minutes)
- Reduce total travel delay (total daily travel delay reduction of 827 hours, a 42.2% decrease)
- Increase the maximum flow of traffic through known bottleneck locations, making traffic flow more stable and resilient to breakdown
- Improve safety by reducing the formation of bottlenecks, flow breakdown and the likelihood of rear-end and side-swipe crashes.
Source: SMART 25 Managed Motorways Pilot Demonstration – Performance Evaluation Report, Colorado Department of Transportation
How has the collaborative process between WSP teams helped deliver the SMART 25 Managed Motorways Pilot Project?
Scott Pitera: WSP partnered with VicDOT and Transmax for delivery of the SMART 25 pilot. Transmax, [wholly owned by the Queensland Department of Transport and Main Roads], is the developer and operator of the STREAMS freeway management system that actually drives the CARM system. WSP staff visiting from the US were introduced to the concept and connected with Australian colleagues working on managed motorway projects. WSP staff worked together to connect WSP USA with VicDOT and Transmax, leading to a strategic partnership for the US market. WSP in Australia also provided guidance on the concept during early pilot planning and design stages of the CDOT project to move the project forward. WSP’s intelligent transport system teams meet on a regular basis globally to share knowledge, ensure teams are up to date on key developments and connect our partners to opportunities to develop solutions together.
As the practices and tools available to road agencies for their network operations evolve regionally and around the world, what future advancements do you envision for enhancing the effectiveness of network services and supporting sustainability objectives?
Scott Pitera: Through reducing travel time delay, improving travel reliability for the movement of people and goods and improving safety and reducing emissions through the reduction of stop-start traffic patterns, CARM can deliver significant benefits to a congested freeway corridor. As realized in Melbourne, these benefits continue to increase as CARM expands to a network scale. Additionally, other complementary tools, which are used in Melbourne and across Australia, such as variable speed limits and lane-use management systems, can further optimize operations for even greater safety and emission-reduction benefits.
In the not-so-distant future, the real-time data needs of these systems may be sourced from the vehicles themselves through CAV [connected and autonomous/automated vehicles] vehicle applications, reducing reliance on roadside vehicle detectors.