With the US Department of Transport committing to the use of ITS networks to reduce congestion, David Moss, Business Development Manager at GarrettCom Europe, looks at some of the hidden costs in implementing these systems and highlights where low-cost solutions might be found. Ethernet, he says, is the way forward.

With the modern dependence on highways for local and long-haul transportation, and the potential for congestion and incidents that can tie up freeways and surrounding surface streets for hours, traffic management has to improve.

The US Department of Transport (USDOT) estimates that traffic congestion in one form or another is costing America more than $200 billion a year. Americans are spending 3.7 billion hours and using 2.3 billion gallons of fuel each year sitting in traffic jams. And congestion is taking valuable time out of every day, with both economic and social costs.

Over the past 20 years, US citizens’ real incomes have risen by roughly 100 per cent, and population has grown by 28 per cent. The result is more people with greater means to travel further – in that same period, highway passenger travel has grown by 49 per cent. USDOT has looked at demographic trends which will impact on its ability to reduce congestion. The US population topped 300 million in 2006 and is estimated to grow to over 350 million within the next 20 years. At the same time, vehicle miles travelled are projected to increase by 60 per cent by the year 2030.

Reducing urban congestion has become a key goal for USDOT, and the increased use of Intelligent Transportation System (ITS) networks and new incident management approaches are seen as primary enablers. The initiative is defined under The National Strategy to Reduce Congestion on America’s Transportation Network.

The schedule for the various Reduced Congestion strategies extends through fiscal years 2006 to 2011. There are very clear milestones and measures for success; in particular, performance measures for urban congestion include a reduction of congested travel to 31 per cent or less nationwide by 2011.

There is a strong emphasis on the adoption of congestion-reducing technologies through the ITS programme: USDOT has concluded that widespread deployment of ITS and related technologies will not only relieve congestion but also make travel on the highway system more reliable and predictable. In short, transportation technology is a positive external factor that is likely to help reduce congestion. However, there is also recognition that the operational and technological improvements must be cost effective.

The Bush Administration proposed $65.6 billion in budgetary resources for FY2007 to support major investments in transportation that are vital to the health of the US economy and American way of life, but these funds will be spread across the whole gamut of transportation systems and support the complete spectrum of congestion-reducing measures, including new highway construction plans. These resources have to address the needs of the current system in a responsible way, while laying the groundwork for the future.

Cost is a major issue which impacts on two levels, one of which is immediately obvious whilst the other, which is potentially more serious, only becomes clear once the first costs have been incurred. A centralised traffic control network topology comprises two major pieces. The edge portion of the network connects devices in intersections into the intermediate local collection points. The backbone portion carries the traffic from intermediate local collection points to the Traffic Operations Centre (TOC).

In both edge and backbone applications, the traditional practice in traffic control has been to follow telecommunications’ lead. Telecommunications solutions have focused on serial connections, reliability and outdoor-hardened equipment – and these were readily available.

Fibre has emerged as the backbone medium of choice because it provides unlimited bandwidth and is relatively immune to electrical noise, contaminants and other intrusions. With a range of 12.5 miles (20km) for 100Mb standard single-mode fibre implementations, it provides secure transport within the typical range of a TOC. At the edge portion of the network, voice-grade and T1 serial lines have previously been the edge protocols of choice for installation at the intersection for managing traffic lights, pedestrian crosswalk signals, traffic counters and other light duty activities.

Consider, now, the emergence of video cameras for traffic control and management applications: video cameras can provide immediate, full-motion feedback at traffic hotspots. As well, they offer better information for emergency vehicles, pedestrian and vehicular safety, public security and other control and management functions that are the outgrowth of increasing traffic congestion.

The cost of these cameras will always be a fixed, known parameter. Combine this with the fact that more than 80 per cent of all traffic intersections are already wired for data transmission and surely we are well on our way to implementing a cost-effective, congestion-busting ITS programme?

There is a problem. Live video and other new technologies promise more information and more responsive traffic control but at the cost of greatly increased bandwidth. Modems running at 56Kb and T1 lines running at 1.544-3.152Mbps cannot keep up.

The edge bandwidth, typically 25-100Mb with live video, needs to support one intersection or a subnet consisting of several intersections. Bandwidth is heaviest here, running from 100Mb to 1Gb, and outages cannot be tolerated. So we need to look at upgrading the edge portion of the network.

There are issues with the backbone, too. Protocol choices have traditionally been SDH, SONET and ATM. Although live video massively increases the required bandwidth, these protocol choices are, on the face of it, able to cope. However, bandwidth over SDH, SONET or ATM protocols is metered, as is the telecommunications tradition, so cost increases with bandwidth.

This, then, is the hidden cost of implementing ITS strategies. The upgrade to new technologies at the edge is one thing, but the cost of drawing the data from those technologies is quite another.

The low-cost alternative
Ethernet is quickly emerging as the protocol of choice for incorporating video cameras at traffic intersections and for connecting to cameras monitoring interstate highway traffic. With the recent introductions of the 1Gb and 10Gb Ethernet standards, it is also a strong contender for carrying huge amounts of data back to the TOC. The scalable Ethernet standard encompasses a variety of bandwidths and, with the unlimited bandwidth capacity of optic fibre media, promises inexpensive and relatively painless upgrade paths for systems as traffic control technology evolves. In a traffic control network with video, over 95 per cent of the data moves from the edge to the TOC; very little flows down.

Networks like Ethernet based on IP packets are well suited to this unbalanced load. In addition, where SDH, SONET and ATM systems are usually heavily oversubscribed, Ethernet networks can more readily pass all the data through the backbone, making an Ethernet-based traffic control network more responsive when demand is greatest. Best of all, Ethernet offers a much more attractive cost structure.

Ethernet has always had both bandwidth and cost advantages over serial telecommunications lines. However, office-grade Ethernet products are designed for clean, air-conditioned environments and are incompatible with the heat, humidity, dirt and electrical interference common to traffic control boxes and other outdoors applications.

Once Ethernet’s performance and cost advantages were recognised in other markets, such as telecommunications and industrial control, new Ethernet boxes hardened for outdoor use started to become available.

They have metal cases that are sealed to keep out contaminants and use premium components rated for temperature extremes along with special thermal design techniques. Combining the hardy features of the fibre medium with Ethernet product designs that could withstand extended temperatures and particulate contamination are all benefits that make Ethernet ideal for the ITS market.

Government support for Ethernet in the USDOT ITS initiative is growing and early implementations of Ethernet-based systems are already paying dividends. The state of Texas has one of the largest state-maintained highway systems in the US. Over 75 per cent of vehicle miles travelled in Texas are on Texas Department of Transportation (TxDOT) maintained roadways. To monitor and manage traffic flow, and to view accidents for better emergency response, TxDOT wanted to send video back to the Fort Worth Traffic Control Center (TCC) from 150 of the busiest intersections in the city.

As the new part of the traffic management system, TxDOT decided to implement video cameras at different points in the intersections. Network managers had determined that installed serial communications lines were simply not fast enough to allow traffic controllers to get the video information and respond in time. Besides bandwidth and cost, an additional challenge was availability. The equipment needed to be installed and operate in enclosures that were not temperature controlled and be reliable in harsh weather. TxDOT elected to use hardened industrial-grade Ethernet switches from GarrettCom and wireless Ethernet throughout the intersections and in the communications grid back to the TCC.

Previously, when there was a problem at one of the intersections off a Fort Worth exit ramp, traffic tended to back up along an extended section of the highway. Now the new video traffic management system enables TxDOT in Ft Worth to get accurate video images from the intersections quickly and accurately. The combination of wired and wireless Ethernet enables personnel at the TCC to better manage traffic and reduce delays from accidents. The video data system also helps TxDOT personnel to relay accurate information quickly to emergency response personnel.

In Virginia, which has the third-largest state-maintained highway system in the US, the Pinners Point interchange in Portsmouth offers commuters easier access to the Midtown Tunnel to Norfolk and provides a more direct route to the Portsmouth Marine Terminal while relieving traffic through the historic Port Norfolk neighbourhood.

It features a state-of-the-art high-speed Intelligent Traffic Management system built around hardened Ethernet switches from GarrettCom and optic fibre cabling to provide the bandwidth and reliability necessary to relay vital information from the 170 field controllers, over-height vehicle detectors, traffic sensors that detect changes in traffic flow and video cameras spaced along the roadways at Pinners Point to pinpoint incident sites.

With this system, controllers stationed in the TCC in Portsmouth can be ‘virtually there’ when a traffic incident occurs. Virginia Department of Transportation controllers can now activate dynamic messaging signs and alarms, and even lower a gate to close the tunnel between the time an over-height vehicle alarm is initiated and the time the offending vehicle would otherwise enter the tunnel, thus reducing tunnel traffic jams and incidents.

Because of Ethernet’s high bandwidth, traffic controllers can respond to incidents throughout the interchange within seconds, sending information to electronic message signs and Highway Advisory Radio to give commuters and travellers up-to-the-minute traffic information. Controllers can also contact one of the TCC’s Freeway Incident Response Teams, and alert or direct emergency personnel as needed.

All over the US, as ITS systems are implemented and demand for bandwidth grows, Ethernet is emerging as the preferred protocol, delivering high-performance traffic management systems in line with the US DOT’s Reduced Congestion goals, whilst meeting the demands for cost-effective solutions.

PUBLICATION: ITS International
DATED: 22nd May 2007