How does public transport respond to warm weather?

Travelling by public transport can feel unbearable during high temperatures.

Here we answer some of the key questions around travelling in a heatwave.

- Is there a maximum temperature that buses or trains are allowed to operate at?

There are no specific guidelines covering a maximum temperature on public transport, and it is not specified in health and safety laws.

- Are trains air conditioned?

While many modern fleets do have air conditioning, some older ones do not.

South Western Railways says its oldest trains do not have this facility due to their age and design. It would require a "major modification" including rebuilding all the roofs of each coach and adding additional power units costing around £50 million.

Instead the trains have opening windows and an air ventilation system that circulates air around the train.

South Western Railways
South Western Railways

- What about buses?

The majority of buses do not have air conditioning because the systems use up a lot of energy.

Fitting buses with air conditioning requires larger engines to provide more power and bigger wheels to carry the extra weight.

This would consume more fuel, increase emissions and reduce the number of seats.

Many bus operators do not believe this is economically or environmentally viable to upgrade their fleets with air conditioning.

- What about London Underground?

A fleet of new S-stock trains with air conditioning are in operation across the Circle, Hammersmith & City, District and Metropolitan lines.

Deep-lying Tube lines do not have air conditioning due to a lack of space.

London Underground
London Underground

- Do bus or train operators have the heating on in summer?

Some passengers complain bus and train operators turn the heating on in the summer because hot air is being blown into their faces.

Unless there is an error with the heating system, this is not the case.

Ventilation systems move fresh air around the bus and if the ambient temperature is high then the air will be warm.

- What is the advice for passengers travelling in hot weather?

Passengers are advised to carry a bottle of water and not to travel if they feel unwell.