What is a Rail Profile?

Rail profile is a term describing different types of railway tracks according to their unique cross sectional shapes. This method of description has been used to identify rail track types for centuries with early examples including the Barlow, Bullhead, and Vignoles rail profiles. Modern conventional train track sections are generally standard, rolled steel members with a basic I shape consisting of a head section and a web and a foot section. Most rail profiles also carry weight identifiers expressed as pounds per yard (lbs/yd) or kilograms per meter (kg/m).

The humble railway track section has followed a fairly meandering evolutionary path since the carriages of the first horse-drawn wagonways trundled sedately along on wooden rails. Since then, horsepower has given way to steam power and the modern diesel and high speed electric trains of today. The railway track sections themselves have grown in strength and durability from those early wooden and cast iron rails to the flanged T and LR55 profile types of today. Although the "fish-belly" tracks of the early 1800s are a far cry from modern rails, the rail profile system of identification from back then is still in use today, albeit with fewer common profiles.

The profile of a track section is the shape of the rail when viewed in cross section. In the early days of rail transport, several different track profiles were used as the technology advanced and trains became heavier and faster. Common examples of the time included the Bridge rail, Barlow rail, Bullhead, and Vignoles profiles. Each followed a basic I design pattern with the major differences being the size relationships between the three main parts of the track sections. These parts are the head, web, and foot of the rail profile. The head is the wider top part of the I on which the trains wheels bear, the web is the thinner upright support, and the foot is the wide bottom of the I which is fastened to the ties or sleepers.

The basic I rail profile is still in general use today and is commonly known as a flanged T profile. This rail shape features a foot which is considerably wider than the head and a fairly high web section. These track sections are also produced in different sizes grouped by weight per length. These are identified by kilograms per meter or pounds per yard values with common examples being 30kg/m (60.5lbs/yd) and 60 kg/m (121lbs/yd) for railway tracks and 5.95 kg/m (12lbs/yd) for crane rails.

Another modern rail profile design is the LR55 system. This rail profile is used where tramway tracks are imbedded flush into road surfaces. The LR55 system consists of a flanged, V shaped rail which is laid onto a polyurethane mastic cushion in a concrete trough laid flush with the road. This allows for minimum noise transfer to the tram and prevents electrical leakages from the powered tracks.