The Highways Agency has determined that it could make huge savings in carbon emissions and millions of pounds a year could be cut from its energy bill by turning off the lighting between midnight and 5:00am on stretches of motorway that are lightly used between these hours, and that doing so will produce only a tiny increase in the risk of accidents. The control systems currently installed for motorway lighting make no provision, however, for timed operations.
For this reason Minos Systems, a company with wide experience in implementing automatic control for highway lighting installations, was approached to devise a control system that could be easily retrofitted to existing lighting feeder pillars along the motorway margins.
Given that around 1,800 miles of motorway in the UK has lighting installed, it was clear from the outset that, even if automatic timed operation were to be implemented for only a small part of this mileage, a large number of control systems would be needed. It also became clear very quickly that no two control systems were likely to be identical, as every feeder pillar was unique in its internal arrangement and capabilities.
The basis for the control solution was easy to decide – it would be powerline switching, a technology in which Minos Systems specialises. This relies on sending signals from the control system, via the existing power wiring, to a switching module installed in each lighting unit. The need for new cabling between the control system and the lights, which would have been very difficult and costly to install, is therefore eliminated.
The engineers at Minos Systems still, however, faced the challenge of developing a control system that was cost effective and could be installed quickly and easily in the feeder pillars.
And there were additional requirements. Despite the pillars being nominally weatherproof, many of them were found to allow the ingress of water to a greater or lesser extent and, with the water, contaminants such as the salt that is used to deice the motorways during the winter. Although they were to be mounted within the feeder pillars, the control systems would, therefore, need their own protective enclosures.
An obvious solution would have been to design a separate control system to suit each feeder pillar and build it into a standard enclosure, ready for installation on site. In view of the large number of control systems that were needed – 14 for the pilot project alone, with the potential for hundreds more in the future – the engineers at Minos Systems decided, however, that producing a separate design for each control system would be costly and inconvenient.
What was needed was a modular approach, where a number of standard modules could be designed and then combined as necessary to suit the requirements of a particular feeder pillar. But what kind of enclosure would be sufficiently flexible to use in this type of arrangement? After carefully examining the available options, the engineers found that the answer was the Enystar combinable enclosure system from Hensel.
This versatile system comprises enclosures manufactured from high-grade impact-resistant thermoplastic materials. Hensel Enystar enclosures are offered in a range of sizes, and are available with either closed sides, or with open sides that can be fitted with cover plates. The open sided versions can also be combined in virtually any combination to produce larger assemblies that offer IP65 ingress protection throughout.
Other options for this enclosure system include transparent or opaque hinged or separate doors and a wide variety of locking mechanisms. Particular benefits in this application are that the enclosures are totally corrosion proof, and that they are suitable for use over an operating temperature range of -40c to 120C .
For their motorway lighting control systems, the Minos Systems engineers selected Enystar enclosures with open sides, and with transparent hinged doors. They designed each element of the control system – such as the control module itself and the circuit protection – so that it could be accommodated in one enclosure. For each feeder pillar, the enclosures containing the required elements were simply assembled together and wired, an approach that delivered big savings in both time and money.
"The Hensel Enystar enclosures are not only versatile, they’re also very easy to work with," said Joe Jervis, Senior Project Engineer at Minos Systems. "They connect together quickly and easily, and they are very robust. In fact, a complete assembly comprising multiple enclosures and all the equipment in them, weighs in at around 40 kg, and we can lift it by its ends without it even sagging!"
"The material from which the enclosures are made is easy to drill and cut. In addition, as it’s an insulator in adds to the safety of the installations. The transparent doors are another big benefit, as they allow the status of, for example, circuit breakers to be seen without the need for the enclosure to be opened."
Minos Systems has to date supplied 14 motorway lighting control systems based on Hensel Enystar enclosures. In addition to timed control, all of these include provision for the lights to be turned on from the motorway control centre, using messages sent via the mobile telephone network. This added functionality is particularly useful in accident and other emergency situations.
Control systems in the initial batch have been installed in the feeder pillars on the M6 in Lancashire between junctions 27 and 29. Because their flexible design allowed the assemblies to be adapted to precisely the requirements of each feeder pillar, they were fast and easy to install. Typically, the work took only half a day for each pillar, including the time needed to strip out the existing equipment.
So successful is the modular design of the control systems developed by Minos Systems that the company has now received orders for a further 50 assemblies. These will shortly be installed on the M5, the M42 and a further stretch of the M6.
"The flexibility of the Enystar enclosure system, available from Ceenorm UK, enabled us to come up with an effective, versatile and cost-effective solution for motorway lighting control," said Joe Jervis, "and it’s now delivering benefits all round. For us it’s very good business, for the Highways Agency it means big savings on energy costs, and for the planet it means a substantial reduction in carbon emissions. Boxing clever sums it up very nicely!"