Wooden Rail Sleepers And Concrete Rail Sleepers for Railway System

Traditionally, rail sleepers (known as rail ties in the US) are made of wood. They can be softwood or hardwood. Most rail sleepers in the UK are made of softwood, although London Underground uses a kind of hardwood called Jarrah wood. Rail sleepers are normally impregnated with preservative and oil coating. Under good conditions, wooden rail sleepers can last up to 25 years. They are easy to cut and drill and used to be cheap and plentiful.  Nowadays, they are becoming more expensive and other types of materials have appeared, notably concrete and steel. Concrete rail sleepers are the most popular type of rail sleepers around the world. Concrete rail sleepers are much heavier than wooden ones, so they resist movement better. They work well under most conditions but there are some railways which have found that they do not perform well under the loads of heavy haul freight trains. Concrete rail sleepers offer less flexibility and are alleged to crack more easily under heavy loads with stiff ballast. They also have the disadvantage that they cannot be cut to size for turnouts and special trackwork.  A concrete sleeper can weigh up to 320 kg (700 lbs) compared with a wooden sleeper which weighs about 100 kg or 225 lbs. The spacing of concrete sleepers is about 25% greater than wooden sleepers.  Another rail sleeper design consists of two concrete blocks joined by a steel bar. It is 30% lighter than a regular concrete rail sleeper, allowing it to be moved manually. This compounded is popular in France (where it is called Stedef) and for some lighter track forms like those used for tramway systems. Steel rail sleepers are also now used on more lightly used railway, but they are regarded as suitable only where speeds are 100 mi/h (160 km/h) or less. In the US most rail ties are made of oak soaked in creosote. They can last up to 20 years. Most Class 1 RR's will replace them after 5-10 years and then sell them as used. Concrete rail ties are popular in the western US and on passenger lines in the east. Recently, composite rail ties have come on the market. They are made of something like old rail tires and recycled plastic. They can be used and spiked like regular rail ties, cost about 50% less and save on trees.