Why are There Gaps in Railroad Tracks?

Railroad tracks are rather simple structures. After construction crews put down a good foundation of earth and crushed stone for the rail bed, the track is built using timber (often called ties) and steel rails that run parallel at a designated width to accommodate the wheels of the train.

Rails are manufactured and transported to the site of new railway construction. They have to be in manageable lengths (the longer the better of course). They have to be placed close enough so that the train can move smoothly, without a large gap between the sections. For many years, workers used metal plates that helped hold the sections in place and close together.

This has changed somewhat in recent years because of the high-speeds at which trains run. Steel rails are often welded to make the path smoother and more continuous.

While every effort is made to make the rail bed as firm and solid as possible and to place the ties and rails for minimum movement, there will always be some motion when the train rolls along the tracks. Trains weigh hundreds of tons and put extreme strain on the rails, ties and bed of stone. In addition, changes in temperature will cause even the steel rails to expand and contract somewhat. Having some gaps can help with this very slight movement and keep the rails from buckling, rising up etc.

Various methods are used to connect rail sections, with crews using a different number of bolts. There are a few different ways to place the bolts in relation to the gaps as well, all in an effort to provide the most stable line of rails. Not only are small gaps left between the rail sections so that the pieces can expand and contract, the bolts used in many railroad construction systems are oval, which can also allow for some movement with the changes in weather.

In some countries the gaps in the rail ends are across from each other, while in other countries the gaps are staggered in an effort to keep the tracks as stable as possible. Train passengers have long identified the sound of wheels hitting the small gaps. This “clacking” sound is one of the memories that many older citizens carry with them.

But newer rail lines are made with rail sections welded together. This allows for a much smoother and quieter ride on faster trains. The practice of using welded rails is much more expensive, primarily because more labor is involved in joining the sections. In many locations around the globe railroad companies still use bolted rail sections because of the lower cost. Welded rails must be placed and welded very carefully of course and other provisions must be made for expansion and contraction that will occur.

Railroad companies use such devices as “clips” or “sleepers” with welded rail systems. These help reduce the movement of the rails after they are welded in place. As techniques are fine-tuned, welded-rail tracks become more common.