The greater Cairo metro system will lower its speeds on Sunday as the city is registering temperatures over 43 degrees Celsius in a move that aims to avoid added friction on the tracks that could cause derailment, Metro Authority Spokesman Ahmed Abdel-Hady told state news agency MENA.

The metro, which operates in throughout the capital city and surrounding areas and runs at a speed of 80 kilometres an hour, is constructed both under and above ground. Abdel-Hady noted that speeds will only be lowered above ground.

Speeds on the first line will be lowered to 50 kilometres an hour. Speeds on the second line will be lowered to 60 kilometres an hour.

Increased temperatures cause tracks to expand, and friction from the train’s speed causes additional heating that can lead to derailment.

The country’s heat wave has started on Saturday and will last till Tuesday, with BBC reporting temperatures in Cairo could reach a high of 47 degrees on Sunday.

Three metro lines in the capital currently serve over 3.5 million straphangers daily.

A fourth and final phase of the third metro line are scheduled to be completed by 2017.