End in sight for motorway misery
November 22nd 2007 A pilot scheme on a busy section of the 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 will see advanced traffic management schemes introduced 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 implemented across the country will report back to Ms Kelly next Spring.
The M42 trial took place between junctions 3A and 7 of the M42, for 12 months across the 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.
The result of the trial was an improvement in journey times by 27%, a reduction in fuel consumption by 4%, and a reduction in vehicle emissions of up to 10%. Further, 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.
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 technology. For this reason Mouchel Parkman chose GarrettCom's field hardened 6K16 managed industrial Ethernet switches with their 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 ideally suited to connect the locations on the roadside. 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.
The £150m scheme around Birmingham will use the same sophisticated technology to control and monitor speed, with a new control centre established to watch over the roads using the networked video cameras.
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