The railway network has always been important in Britain, not just for every day travel, but also for the transportation of good and services. Unfortunately nature and the elements can ruin even the best laid plans. Weve all seen the headlines about railway disruption whether thats the wrong type of leaf on the track or the big freeze that brings the country to its knees: we all no doubt moaned about the fact that our journey has been affected by such apparently trivial problems. But have you ever wondered how the train companies manage to keep the tracks open, or considered the sort of problems they face trying to achieve this?

Well, it isnt as simple as you might think. Its not simply a case of spraying de-icer here and there, or applying liberal quantities of weed killer over the tracks and the surrounding area. In an environmentally-conscious age, such practices are simply unacceptable: the application of any herbicide or chemical compound has to be selective in order to protect the wildlife. So how do they achieve this? They use the latest Total Drop Control (TDC) spray applicators along with GPS technology.

However there are still problems that they need to overcome. The traditional methods of using a weed killer train have worked effectively for a long time, but environmental concerns now mean that the companies have to be more careful with the application of any chemical substance in the vicinity of the track and the surrounding areas. Using too high a concentration of a chemical means the wildlife may suffer: certain weed killers have been proven to kill species like the lesser spotted newt. Using too low a concentration of weed killer simply means that the problem will re-occur. New technology ensures that the delivery of the correct concentration of herbicide in an ecologically-approved way which avoids any risk of point source pollution. The dispensing equipment is fixed to the train itself and is controlled by GPS technology: the flow of the chemical spray is linked to the speed of the train and monitored by a speed sensor. Unfortunately GPS technology has its limitations and isnt always suitable: Britains railways have lots of tunnels and many trees which can affect the accuracy of the equipment.

There is a solution however, and that is using doppler radar technology. Doppler non-contact radar speed sensors are already widely used by UK rolling stock engineers, and are valued for both their accuracy and their low cost. The new single beam and dual beam sensors provide accurate, independent speed and distance measurements in many railway environments. They are currently in use of both test tracks and the main lines.

The Doppler radar technology has been refined to give accurate speed and distance data which is free from the errors normally associated with wheel slip, GPS blank areas or surface changes. Because the non-contact radar Doppler speed sensor device is fitted independently from the train wheels it is not affected by wheel slippage. These sensors also indicate the direction-of-travel, and offer both digital pulse and/or analogue voltage outputs.