Plug and play approach unifies workzone ITS

Caltrans District 7 is finalising a ConOps document which will detail a plug-and-play to work zone ITS operation. The organisation's Allen Z. Chen elaborates.

Before August is out, on current planning, the 923 California Department of Transportation (Caltrans) District 7 (which covers Los Angeles and Ventura Counties, with a combined population of close to 11 million people) intends to have finalised a Concept of Operations (ConOps) document dealing with Work Zone Transportation Management Systems (WZTMS). The intention is to bring into being a unified, readily applicable approach to the use of ITS systems in work zones and get away from the historical acceptance of transportation management breaking down at locations where construction or remedial work is taking place. This has led to a three-pronged approach to work zones operation which is designed to sustain congestion monitoring and improve both safety and mobility.

The Los Angeles area has a long history of transportation management systems operation. Implementation stretches back to the early 1970s and there is now a considerable amount of data-gathering and monitoring infrastructure in place. From a technical perspective, all operations are cable-based. Data networks run up the hard shoulders of major routes and gather information from in-pavement sensors. Construction or maintenance work, therefore, tends to disrupt the ability to sustain monitoring of conditions in and around the area concerned.

Sustaining capabilities

"The ConOps document looks at how to sustain capabilities which would traditionally be lost. In the first instance it will establish policy and practice using today's technologies," says Allen Z. Chen, Senior Transportation Engineer for ITS with Caltrans.

Paying particular attention to the issues of lost communications, systems interaction (including the more common use of portable devices and how these will interact with permanent infrastructure), incident response and public information, the document stresses the use of IP addressable devices.

With congestion such an issue locally, LA freeway operations emphasises the use of data to drive system-wide management strategies such as ramp metering. Information on traffic movements is also relayed back to the local Traffic Management Centre (TMC) to be displayed on local Variable Message Signs (VMS) and passed on to local media. Looking beyond current practice, the aspiration is to gain from work zones - which Chen describes as "bottlenecks due to lost capacity" - current traffic speeds and capacities which will assist with lane management. Better real-time information provision to those actually travelling through an area where work is underway is also an aim.

"Elsewhere in the US, the approach seems to be more fragmented," Chen says. "But, for instance, if I can detect incidents downstream of a work zone then I might need to put out advisories within the zone itself." District 7 is responsible for over 500 lane miles of urban freeways. It handles 100 million vehicles a day and deals with over 1,000 incidents of all kinds, from minor to major, every 24 hours. However, with only around three Traffic Management Centre (TMC) operatives on shift even at peak hours, there is a huge reliance on data collection with CCTV verification. With a total of 435 cameras in operation, Chen puts network coverage at over 80 per cent.

"Resurfacing work damages monitoring and communications infrastructure," he continues. "Traditionally, we would ask contractors to replace that which was disabled or damaged towards the end of a project. But with work zones regularly in place for anything between 18 and 48 months, that's a long time to be without management capabilities on a network which already faces severe pressures."

Addressing the need

The work for the Concept of Operations has taken a structured approach, identifying needs and then ascertaining the availability or otherwise of capabilities.

Chen: "We've evaluated devices which meet work zone operations requirements and then specified their use going forward. We've set out to develop a 'cookie cutter' solution, including wireless connectivity to that specified equipment. Contractors will therefore be able to deploy, acquire cellular services and, effectively, plug straight into the central system. There'll be no need for specialised solutions." TMC operatives will enjoy M-JPEG snapshots of what is occurring within work zones. Once construction or remedial work is completed, cameras will be reconnected to the fibre backbone and provide streaming images.

"Lower-quality information is better than none but we'll still be able to sustain an operational capability," says Chen. "Wireless has two disadvantages: cost, because services are leased; and bandwidth when compared to a fibre solution."

Phased approach

Work zones technological solutions are divided into those achievable in the near-, medium- and long-term. Near-term solutions, those which are realisable within a year, include updates to traffic management plans to include portable ITS devices, deployment of speed detection and display systems, deployment of variable speed limit systems, and TCP/IP network connections via fibre or wireless. Mid-term solutions, realisable within two-three years, include CCTV surveillance/monitoring, Highway Advisory Radio capabilities, queue end warning systems, integrating portable ITS systems which are provider-independent, and integrating ITS devices using any wireless communications provider network. Long-term solutions, those taking four years or more to bring about, include dynamic lane merging systems, speed monitoring display systems, independently managed work zones within the overall advanced traffic management system, and alternative route guidance via cellular phones.

"You have to remember that 'long-term' really can mean the long term," Chen continues. "Capabilities such as end-of-queue monitoring and speed detection and display are things which we aspire to but don't have even in our central system. But it is possible to do these things locally in work zones."

Work zones are in many respects also proving grounds, he notes: "Major incidents are akin to work zones in that you have a localised loss of capacity. Right now, our response strategies are manual but out of the work zone study we've learned something. Even though work zones are planned closures, there's a loss of capacity and queuing. But even with today's technology it's possible to put in radar, activate signage and so on." Although portable systems' performance is getting better, there is still a tendency for them to operate as local decision systems only. It can lead to distrust on the part of the road user, as the information presented by work zone changeable message signs, for example, can conflict with that on the centralised system controlling the wider area.

"Portable systems should have the capability of collecting data and our ConOps will look to make them a part of the regular system, providing speed and occupancy information that can feed into travel time advisories," says Chen. "That will benefit ramp metering rates and VMS messaging upstream."

Standards compliance

NTCIP compliance is a feature of the document but so is pragmatism. Interfaces may not have all of the listed NTCIP attributes but Chen says that this may not in fact be necessary: "NTCIP is a moving target. Also, our fixed system isn't totally compliant. That's a product of having been developed in the 1970s, updated in the 1980s and then looked at again in time for Y2K. It also underwent an IT upgrade in 2005. If we waited for full compliance we'd never deploy anything. But we do support the concept.

"We have a legacy interface but what is important is that we share data with partner agencies. We run client website services to port data out, for instance."

Although some of the desired technical solutions have yet to be realised, Chen says that integration is the key focus. Caltrans won't for example be developing new automated incident detection or adaptive ramp metering systems as a part of the ConOps work. Of all the technologies identified as being of potential use in work zones, speed advisory and queue detection systems are those he'd most like to have. At present, the deployment of queue-end warning signs is a manual affair.

The first full application of the new methodology is already in hand. This will be on a $1 billion freeway widening project on the I-405 corridor. This is already in the bid stage and, budgetary pressures notwithstanding, is due to start in October.

Once it is fully finalised, Chen says that he is more than happy to share the content of the ConOps document with other agencies across the US.