Since late summer, the Nottingham Tram network (NET) has more than doubled in size with the opening of its southern and western extensions to Clifton and Toton respectively. 27 new stops have been added, making a total of 51.

The new lines are a mixture of street-running and dedicated routes, the most spectacular feature being the new stop at Nottingham Midland station located on a bridge spanning all six platforms. Those with a longer memory will recall that there was once a bridge carrying the erstwhile Great Central main line across the station at the same spot. Who would ever have placed money on a new bridge being erected some 45 years later for a similar transport purpose.

The NET follows standard practice for tram control with stop/go signals being an illuminated horizontal or vertical white bar – also a diagonal bar to indicate a route divergence – with most points being ‘spring’ operated except for six at key junctions which are motor-controlled with locks. ‘Drive on sight’ is the normal routine, the signals being used at road intersections in conjunction with normal traffic lights and at places where the routes diverge. The pattern of service is from Clifton South to Phoenix Park and Toton Lane to Hucknall, thus integrating the new extensions with the original lines to the north.

A seven-minute service operates on all lines during the morning and evening peaks, with 10 minute frequency during the daytime and 15 minutes in the early morning and late evening.

The extensions involved laying 17.5km of new track and the purchase of 22 new trams, making 37 in total. The entire network expects to see 20 million passenger journeys each year, 55,000 of these being regular commuters.

Controlling the network

The main depot is at Wilkinson Street, north of the city, where trams are cleaned and maintained, and also where the main control room is sited. Most desks in the latter are multi-functional with the operators’ screens being able to access more than one facility.

Trams are equipped with GPS positioning, so the location of every tram in service can readily be seen. A red/green light system on the illuminated route diagram indicates whether a tram is late or running early so that operators can take whatever action is necessary to get back to the scheduled timetable. It has to be remembered that, with the various road junctions and street running sections, there are many occasions when disruption can occur. A video wall provides the controllers with a constant picture of the actual minute-by-minute operation.

A CCTV viewing suite has also been provided at Clifton Park and Ride that can view the CCTV network, and the security officer is able to take control of the cameras from this location. Inside Out Group has also been successful in obtaining the security contract with Nottingham Trams Limited and provides the security services at this site.

Viewing the operationIMG_3376 [online]

Constant video surveillance is a necessary part of any modern tram network and Nottingham is no different. For the extension lines, a contract was awarded to Inside Out Group, a local firm that has come to specialise in CCTV monitoring and control. The company’s origin was described in issue 116 (June 2014), the earlier focus being on time-lapse photography which included a record of the new tram bridge being slid into position across the main railway station. The company was revisited recently to learn of the design and implementation of the new CCTV network.

The main contractor for the tram extensions has been Vinci Construction, the civil engineering division of Taylor Woodrow. In partnership, Alstom was engaged to provide the power supply, the overhead line system and the telecommunications network. Inside Out Group had to establish a close working relationship with both these organisations since CCTV provision had to fit in with both building construction and power requirements.

The technical design of the CCTV system is based on IP-specification cameras borne upon transmission bandwidth within the fibre optic cable network provided by Alstom. The cable and transmission network is designed in ring formation that allows full redundancy with automatic re-routing of traffic should a cable get cut. A dedicated four-fibre link is run to each camera from the transmission break out points, ranging from between 5 and 550 metres in length dependant on the distance involved, this being part of the Inside Out Group contract. Typically there are two cameras for each tram stop but more are provided at the main interchanges such as the railway station and at the terminal stations.

The NET extension project is very much geared to ‘park and ride’ encouragement so big car parks have been provided at both Clifton and Toton, with surveillance of these areas being an important requirement. The cameras generally monitor the ticket vending machines and the passenger help points. All have pan, tilt and zoom capability and, should a help point be activated, the associated camera picture will immediately be shown on a control room monitor so that anything untoward can be viewed. Cameras are generally mounted on poles, high enough to be out of reach of vandals and graffiti daubers. Power comes from the station supply, which was part of the Alstom contract. The total number of cameras on the extension lines is 141.

At Wilkinson Street, there are 12 screens in the video wall, eight associated with the two extension lines and four from the original network. Each picture can be called up on the controller’s desk screen from where the camera can be remotely adjusted to zoom in on any incident. The video screens normally show the busy areas of the network such as the city centre and the railway station.

Each camera has an individual IP address to the v4 standard but this might need to be changed to the incoming v6 standard in due course. The zoom capability of the cameras is 22 X optical with digital zoom on top of that if required, the average data rate to each camera being 3.5Mbit/sec. At Clifton, the viewing suite has two large screens, each capable of showing multiple images but able to zoom in on any particular site.

There is continuous recording of all images from every camera with a date and time marker to enable any post- incident analysis to be carried out relatively quickly. The recording capability is huge, with nearly 600 terabytes being needed to meet the 30 day requirement. This requires 14 recorders, each of which can handle up to 250Mbit/sec, which allows for full redundancy and load balancing should a recorder go faulty. The rate of recording for all cameras is full HD 1080 pixels at 25 frames per second every day of the year.

Inside Out Group is not a manufacturer of CCTV equipment and was thus free to select the most appropriate cameras and monitors for the NET requirement. The chosen supplier has been Pelco, a Californian-based company and part of the Schneider Electric Group, with Pro-Vision of Shrewsbury as their UK distributor. These products have more capacity with a better specification and reliability record when compared to others and are proving satisfactory in service.

The future

Inside Out Group is the first to admit that being a local firm was a factor in them being selected as the CCTV contractor. The nearness of its main premises meant a ready base being available for the storage of piece parts, tools and test equipment with experienced engineers immediately available to resolve any technical issues. It also enabled a close relationship with other contractors to be established. The overall NET extension project had a number of delays (the opening was some eight months later than planned) and, with the CCTV having to be one of the last elements to be installed, having the flexibility that a local participant offered counted for a lot.

The original NET lines will shortly have their CCTV monitoring equipment upgraded to the same technical specification as the extension and Inside Out Group is assisting in the design process. This will bring the total number of cameras to around 220. Maintenance of the system will be by specially-trained NET staff. Again, a local presence means that immediate second line assistance can be given if problems arise.

A case study will demonstrate to other customers the Inside Out Group’s capability to provide surveillance systems. It is not a large firm and knows that it must cut its cloth accordingly. Other metro networks and rail depot security are seen as its natural expansion with the knowledge that it will entail providing a facility base at wherever new business is won.