Up to now, steel sleepers have typically been used in developing countries where speeds are modest, the climate is dry, wood is vulnerable to termites, and track circuits are short if they exist at all. Steel is normally more expensive than wood or concrete, and the perception has been that the inverted-U shape favours manual methods of maintenance rather than powered tampers designed to pack stone under flat-bottomed sleepers.
Railtrack is challenging this conventional wisdom in a big way. In the 1980s, British Rail began a phased programme to install steel sleepers on secondary routes. According to Kevin Lane, General Manager, Commercial, of British Steel Railway & Foundry Products, experience gained by BR with the 400 series sleeper using Pandrol’s E-clip was that track circuits did not fail, and mechanised tamping was satisfactory.
Railtrack took up the challenge, and has told its contractors to install 226000 steel sleepers this year against 356000 concrete. In 2000-01, the expectation is that 47% of the 538000 sleepers laid (representing 1·1% of some 47 million in the British network) will be steel. If so, they will start to appear in substantial numbers on main lines.
Two primary reasons are given for paying around £35 for steel sleepers rather than £30 for concrete. The first is that it is unnecessary in most cases to renew the ballast. The old sleepers are lifted out, the ballast scarified and levelled, and the 75 kg steel sleepers placed in position. The other is the high cost of transporting concrete sleepers and ballast to the relaying site. Nested bundles of steel sleepers require only a fraction of the space and lifting capacity. Supplementing these benefits are avoiding the cost of transporting and disposing of old ballast and, in the long term, the ability to sell steel for scrap instead of sending concrete sleepers to increasingly costly landfill sites.
British Steel reckons that this will give an overall saving of £25 per sleeper, and is working with Railtrack to develop 600 series sleepers for heavy haul and high speed lines. Whether or not this comes about, the whole bold venture will attract close scrutiny from track engineers across the globe.