For over ten years, Track Warning Systems have been hyped as a track safety and productivity solution. The reality was minimal use and failed pilot schemes. Automatic Track Warning System (ATWS) installations at 17 key locations in 2002 were soon removed.

The Track 02 system lost its safety approval in 2004 after over a hundred sets had been purchased by Network Rail’s Contractors.

Now times are a changing with Network Rail’s successful large scale LOWS (Lookout Operated Warning System) initiative.

Does this mean a brighter future for Track Warning Systems? With the next generation of ATWS under development, and the McNulty report requiring the adoption of more efficient continental practices, it would seem so. The rail engineer visited ATWS suppliers Zöllner and Schweizer to learn more.

Large scale LOWS use

Zöllner’s Frank Peters states that 230 portable LOWS kits have been supplied to Network Rail’s maintenance teams over the past two years. He knows this equipment is intensively used as Zöllner has been closely involved in its introduction by providing training, a hotline, servicing, repair and annual recalibration.

Frank commented: “Initially we were called out quite a bit, but less so now, as depots get used to the kit.”

Network Rail’s standard NR/L3/MTC/SE0206 “Introduction and Management of LOWS Equipment” specifies the competence for its use and the support to be provided by Infrastructure Maintenance Delivery Managers (IMDMs).

This includes the need to map locations to establish a pre-determined Safe System of Work (SSoW) and to confirm radio coverage.

Training is the same for a LOWS Controller and a LOWS Lookout. LOWS competence is deemed to have lapsed if it is not used within 28 days of initial training. Thereafter LOWS must be used at least 10 times in the next three months and once every three months after that.

Network Rail’s successful LOWS implementation is due to the work of the Track Warning Systems (TWS) Steering Group and those in the maintenance organisation who have driven its introduction. Some depots immediately saw its benefits and made more use of LOWS than others.

No doubt the use of LOWS will increase as, with large scale use, its benefits become clear to all. The time to set up and test a LOWS SSoW is very similar to that for a conventional lookout.

Zöllner consider that by far the greatest use of LOWS is for mobile patrolling. LOWS lookouts remain static but can leapfrog each other as the patrol moves in accordance with the pre-determined SSoW determined by the mapping exercise.

Previously, it was often not practicable for mobile Lookouts to maintain the required sighting distance and mobile workgroups accounted for a large percentage of track fatalities so mobile LOWS use offers a significant safety benefit.

Other advantages are that, at night and in fog, there is no need to impose a 20 mph TSR as the LOWS Lookout can be positioned where the train passes. Also the LOWS Lookout need not be on the rail infrastructure. For example a bridge over a steep cutting offers improved radio coverage, increased sighting distance and a less hazardous situation.

The status quo, our greatest competition

Although both Schweizer and Zöllner supply Track Warning Systems, Schweizer’s Chris Foreman feels that his “greatest competitor is the status quo”. On the Swiss rail network, which is less than a quarter the UK network, he estimates the use of ATWS to be between 50 and 100 per day. Both Chris and Frank estimate that ATWS use in the UK is 5 to 10 per day.

Chris clearly believes large scale use of ATWS would benefit the UK rail industry but feels that current arrangements do not provide sufficient incentive for its use as “Programme Managers have to pay for ATWS but do not get the financial benefit from engineering access savings”.

Chris Foreman considers that the McNulty report’s benchmarking UK rail against European practice should drive increased use of ATWS. Frank Peters thinks that it’s odd that, although the RIMINI standard requires ATWS to be the first consideration for Red Zone working, its use is a tiny percentage of Red Zone working. He also feels that ATWS use needs to be considered earlier in project planning.

Unlike LOWS, ATWS automatically detects trains by rail mounted treadles or sensors. It therefore has a higher safety integrity level with manpower savings, particularly at junctions.

The system consists of detection, processing and warning modules that can be connected by either radio or cables. Although radio offers quicker set up times, radio equipment is more expensive than cables and requires batteries to be changed daily.

Both Schweizer and Zöllner supply equipment to companies who offer ATWS solutions. Schweizer supply their Minimel 95 equipment to McGinley and Rail Safety Solutions and Zöllner supply their Autoprowa equipment to Vital Rail and Rail Safety Solutions.

ATWS works well at sites of a long duration. Schweizer’s system was used during BIRSE’s construction work at Southend Airport station where ATWS facilitated access to speed up the project.

Zöllner ATWS equipment on the Forth Bridge minimised the risk to trains by warning Balfour Beatty’s scaffolders to ensure items are secure as trains pass underneath them.


Zollner control unit. Photo: the rail engineer.

The Next Generation

Both Schweizer and Zöllner are about to launch their next generation Track Warning Systems onto the UK market and expect to get product approval soon.

When approved, both of these systems will have new methods of installing train detection treadles enabling them be set-up in about 5 minutes (i.e. between individual trains) as well as bi-directional radio, to provide the LOWS Lookout with confirmation of the warning on site, and movement detection as a deadman’s safety device. They also use less energy and so are lighter than previous systems.

These improvements will give Schweitzer a fully portable LOWS system. Zöllner’s new system uses a Lithium Battery with its own charge indicator and with an optional increased maximum warning sound to 120dB.

Usually the warning will be less than this as Zöllner’s Autoprowa system has microphones to ensure that the warning is appropriate to the ambient noise level. Schweizer will have repeaters to ensure signal strength.

Both these systems have been already been approved in Europe by independent safety assessors, Technischer Überwachungs-Verin (TÜV).

Frank Peters feels that in recent years Network Rail’s “acceptance process is now more professional” and now recognises TÜV technical approval so that product acceptace primarily concerns integration with UK methods of working.

One of the features of the new Zöllner and Schweizer equipment is that it will no longer be necessary for each control unit to be individually manned.

As a result long worksites need only have one LOWS controller. Frank advises that Amey Colas are keen to use this new equipment so that LOWS can provide warnings to staff on the open line adjacent to their High Output track renewals sites.

Controlling the risk to trains from engineering work

ATWS equipment can be used as part of a safe system of work to protect trains from engineering work, as illustrated by the Forth Bridge example. Chris Foreman advises that Schweizer are developing a system to control the risk to trains on the adjacent open line from machines working in an adjacent possession, enabling such lines to be kept open.

This is based on a 2004 pilot scheme which used ATWS equipment to warn machine operators of approaching trains. When it was then confirmed that machines were not foul of the open line, warning detonators were removed from the line.

This method of working was subsequently included in the Rule Book. While similar, Schweizer’s new system uses an emergency red light and temporary TPWS loop to stop trains unless there is confirmation that the line is not fouled by machines.

Using signalling system to detect trains

Using the signalling system to activate a track warning trains offers instant set up times and reduced costs associated with train detection. It also reduces unnecessary warning as, unlike ATWS, the signalling system takes account of the position of points and trains being stopped at signals.

In the UK, use of the signalling system to provide track warning is confined to small scale use of TOWS (Train Operated Warning Systems) on plain line track, in contrast to more sophisticated systems employed in Europe.

In Switzerland, Signal Controlled Warning Systems (SCWS) have been in use for 15 years. SCWS uses processor modules which, with one exception, take a read-only feed from the signalling system to provide a warning for a section of track within the signalling area.

The exception is the need to delay a signal being cleared to provide adequate warning time. The SCWS systems for the track concerned are generally activated on request by, for example a switch, a radio key or detection of a warning module being plugged in. At some locations the length of the warning module’s cable is the length of track for which protection is provided.

Chris Foreman believes that Schweizer’s SCWS could offer significant benefits especially at busy junctions. These are due to reductions in the number of lookouts, and increased working time by eliminating unnecessary warnings from trains approaching the junction which don’t go through the worksite.

Signalling schemes that install bi-directional working and for which additional track staff protection is required, are a further application. Chris feels it should be relatively straightforward to install SCWS in the UK, especially if initial product approval was confined to a read-only feed from the signalling system.

The Austrian version of SCWS uses the GSM-R infrastructure to receive requests for track warnings and activate warning modules. Frank Peters advises that this project has been under development for ten years and saw its first pilot application this year.

It quickly establishes warning systems for any type of worksite, has no radio reception issues and largely eliminates lineside cabling for warning systems. It is however a long term solution. A more immediate option is the use of GSM-R for track warning systems to eliminate the effects of radio black spots.

A new dawn

For ten years, UK use of track warning systems has been minimal. A new dawn is now breaking with Network Rail’s LOWS use solving the problem of mobile patrolling with significant safety and productivity benefits. Although there is still a resistance to the use of automatic train detection, this must surely change with McNulty’s challenge to improve the productivity of engineering access by learning, in part, from European railways .

The difficulties of introducing automatic systems, including detection by the signalling system, should not be underestimated as many factors reinforce the status quo. Tackling this includes the need for cultural change, gaining workforce confidence, product approval and appropriate contractual incentives.

The signs are that Network Rail now has both the commitment and ability to meet this challenge for which its large scale use of LOWS should provide a springboard. Schweizer and Zöllner are also key players who can provide European proven equipment to ensure that soon the status quo will no longer be a serious competitor.

For further information on Network Rail’s Innovation Process and to submit new Track Warning System proposals click here.