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Industrial Ethernet switches proven in roadside application

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A successful pilot scheme to ease traffic congestion has used field-hardened GarrettCom industrial Ethernet switches and S-Ring redundancy software.

A pilot scheme on a busy section of the UK's M42 motorway to ease traffic congestion at peak times could be rolled out nationwide, Transport Secretary Ruth Kelly has announced. The success of the M42 trial could see advanced traffic management schemes implemented on the busiest stretches of the M6, M42 and M40 around Birmingham, at a cost of £150m, while a feasibility study to see if similar schemes could be used elsewhere will report back to Ms Kelly in the Spring of 2008.

The M42 trial took place between junctions 3A and 7 for 12 months during 2005/06. Its aim was to reduce congestion on the motorway by part-time use of the hard shoulder and variable speed limits. It was also intended to increase safety by using video data, and to offer enhanced driver information about traffic flow, journey times and accidents.

Results included an improvement in journey times by 27 per cent, and an estimated reduction in fuel consumption by 4 per cent and vehicle emissions by up to 10 per cent. Furthermore, the trial also saw the personal injury accident rate fall from 5.2 per month to 1.5 per month on that section of motorway.

IP-over-Ethernet

The key to achieving these objectives was a dynamic monitoring system. When traffic reaches a certain level and is in danger of slowing or suffering stop-start traffic jams, variable speed limits are introduced on electronic Advanced Motorway Indicators (AMI) situated on overhead gantries, with driver information relayed on Variable Message Signs (VMS). If these measures are insufficient, the VMS mounted above the motorway indicates that the hard shoulder is now open as a running lane. In addition to these congestion and information provision improvements, safety is enhanced by a digital enforcement camera system.

The M42 traffic management system was implemented by professional services group Mouchel Parkman, and the company identified, in particular, the need for an Internet Protocol (IP) over Ethernet-based fibre network to connect the cameras to a manned control room in Coleshill. Reliability was paramount, so the fibre optic network required the highest standard in fault tolerance. For this reason Mouchel Parkman chose GarrettCom's field-hardened 6K16 managed industrial Ethernet switches an S-Ring redundancy software.

Each section of road has a 6K16 operating as a master optical switch connecting the fibre optical ring with a transmission station. The ring itself consists of a 96-core fibre optic cable that runs along the side of the motorway. At each gantry the cable is spliced to a 24-core cable. The field-hardened GarrettCom industrial Ethernet switches are used to connect the individual safety cameras to the fault tolerant fibre optical ring.

The GarrettCom 6K16 Switch was also selected because it is housed in a tough steel casing and designed for temperature-uncontrolled environments, and so is suitable for connecting the roadside locations. The switches were required to have their own AC power inputs, rack-mount capability,

secure web management, modularity of copper, fibre and gigabit ports, as well as tag-based virtual LAN (VLAN) functionality.

Road scheme roll-out

A proposed £150m scheme around Birmingham will use the same sophisticated technology to control and monitor speed, with a new control centre established to monitor the roads using the networked video cameras.

And with the concept having proven itself on the M42, Ms Kelly is now clearly assessing its potential across the motorway network nationally. The Transport Secretary said: "What I am doing today is asking the question are there bits of the network, and it could be bits of the M1 or parts of the M6 for instance, where an active traffic management approach might not be a better way to get more people to use the motorway network and improve how reliable their journey times are?"

 
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