Why Crushed Stones Are Laid on Railway Tracks

Have you ever wondered why Kenya Railways places crushed stones, popularly referred to as ballast, on top of railway tracks?

Unknown to many, this practice is a global standard and serves three critical purposes: preventing vegetation growth, providing stability and facilitating drainage.

The presence of ballast on railway tracks is crucial due to its role in preventing potential catastrophic consequences. As a result, Kenya Railways officials regularly inspect the tracks to ensure that this requirement is met.

Kenyans.co.ke dives deep and explains why it is necessary to have ballast on railway tracks.

Kenya Railways officials inspecting the Kisumu Railway Station in July 2020.


Kenya Railways


The primary function of ballast is to provide stability to the tracks

Trains, with their considerable weight and cargo, can exert significant pressure on the metallic rails. 

Without the support offered by ballast, these rails may sink in, leading to disruptions in train operations, and potentially resulting in catastrophic incidents. 

The ballast also plays a crucial role in maintaining proper track spacing, especially during hot weather conditions which can cause metal expansion.

Without adequate ballast, the expansion of metal rails on a hot day can disrupt train movement, potentially leading to derailment.

Prevent Vegetation Growth 

Another crucial role of ballast is to inhibit the growth of vegetation along railway tracks. 

The ballast provides an unsuitable environment for vegetation because it lacks the capacity to retain water or nurture soil-dependent plants.

This is why railway tracks are easily recognizable even after years of disuse or abandonment.

“Leaves can pose a risk to the safe running of the railway and cause delays to trains.

“We manage trees and plants to restore or enhance a preferred habitat or undertake work to manage undesirable conditions where vegetation poses a risk to the safe operation of the railway or to neighbouring property,” global railway constructor, Global Rail explains on its website.

Kenya Railways takes measures to clear vegetation near the railway lines, preventing leaves from falling onto the tracks.

A train pictured on the NCPB Kisumu railway line in July 2020.


Kenya Railways


Heavy downpours can lead to frequent flooding along railway tracks, posing risks to the infrastructure and train operations. 

To mitigate this issue, ballast is the preferred choice, as it facilitates water drainage through its spaces. In contrast, soil retains water for prolonged periods, negatively impacting the railway system.

Flooding can be detrimental by eroding the ballast, potentially damaging the tracks and necessitating speed reductions for trains.

This results in extended travel times for both passengers and freight along the rail network. 

As a preventive measure, officials from Kenya Railways conduct regular track inspections to ensure proper ballast levels. During the restoration of older railway lines, they replace old ballast with new material as required.

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