Air conditioning on London Buses

[Bletchleyite]

Air con is all very well but you have to MAINTAIN it, if an aircon equipped bus has fewer or no opening windows then failure makes it even worse on board than a bus which had no air con in the first place

Certainly. There is a culture in some bus operators that if the wheels turn it goes out and anything else is an optional extra.

 

[Goldfish62]

Certainly. There is a culture in some bus operators that if the wheels turn it goes out and anything else is an optional extra.

Yes, always has been and probably always will be!

 

[Snow1964]

Air con is all very well but you have to MAINTAIN it, if an aircon equipped bus has fewer or no opening windows then failure makes it even worse on board than a bus which had no air con in the first place

Yes, but the London contracts specify what the bus needs. So unlike a poverty operator that will send out anything that moves, if do that in London it has financial penalties.

I will admit TfL enforcement might be patchy, so some might try and get away with it, but I have been on a bus in Surbiton area where a TfL Inspector told a driver that was being reported for penalty for showing wrong destination, so some on street checks do take place.

 

[Goldfish62]

Yes, but the London contracts specify what the bus needs. So unlike a poverty operator that will send out anything that moves, if do that in London it has financial penalties.

I will admit TfL enforcement might be patchy, so some might try and get away with it, but I have been on a bus in Surbiton area where a TfL Inspector told a driver that was being reported for penalty for showing wrong destination, so some on street checks do take place.

Going back a couple of decades when air cooling systems were first specified and installed on the the top deck of buses and cab aircon was also made mandatory it was found that engineers were isolating the equipment.

== Doublepost prevention - post automatically merged: 24 Jun 2026 ==

Air con is all very well but you have to MAINTAIN it, if an aircon equipped bus has fewer or no opening windows then failure makes it even worse on board than a bus which had no air con in the first place

Unlike some buses commonly elsewhere in Europe I would be surprised if TfL ever specified no opening windows. The rule of thumb in their spec is always the maximum number that weight allows, irrespective of cooling system. Thus if the system fails you just end up with a normal toasty bus.

 

[TheGrandWazoo]

Yes, always has been and probably always will be!

Indeed, and provincial operators (often with lower headways) will take the view of saying that as long as the vehicle is legal and roadworthy, then delivering against the timetable is the absolute priority.

I know you know this already but London specifies air-con and it comes at a cost. It costs more in capital, more in servicing, and with diesel vehicles more pointedly, it costs more to run. This is built into the tender cost. For provincial operators, those costs have never been squared with the potential financial benefits. With EVs coming in, that equation is changing.

 

[mangad]

It's an easy one, there are still far too many people with germs flying about so that's probably why windows are open. I'm one of them to be honest but we can't take time off due to strict sickness rules and lack of pay

There are always germs. There always will be germs. Germs aren't going away. Most people don't think about germs every day. Germs are not an issue to open windows constantly for.

Far more likely is people in this country are conditioned to open windows when its sunny "to let the air in". People have been doing it for decades. Reality is, if the bus has good, functioning a/c it shouldn't have openable windows because people WILL open them and the A/C will be defeated.

 

[Bletchleyite]

There are always germs. There always will be germs. Germs aren't going away. Most people don't think about germs every day. Germs are not an issue to open windows constantly for.

Far more likely is people in this country are conditioned to open windows when its sunny "to let the air in". People have been doing it for decades. Reality is, if the bus has good, functioning a/c it shouldn't have openable windows because people WILL open them and the A/C will be defeated.

It should have openable windows but locked with a key so the driver can open them if the aircon fails. This should be a requirement on all air conditioned public transport vehicles of all types. Imagine if 158s didn't!

 

[Goldfish62]

It should have openable windows but locked with a key so the driver can open them if the aircon fails. This should be a requirement on all air conditioned public transport vehicles of all types. Imagine if 158s didn't!

Just straying off topic to answer this - not possible on high speed and many other trains, eg Pedolinos, Eurostar, IETs etc because they're pressurised to eliminate the uncomfortable pressure waves in tunnels.

In any case I'm not aware of any current UK buses with no opening windows. There were some in the 60s and 70s when there were experiments with various pressure ventilation systems.

 

[Bletchleyite]

In any case I'm not aware of any current UK buses with no opening windows. There were some in the 60s and 70s when there were experiments with various pressure ventilation systems.

The only ones I have ever known of are the Borismasters, on which they were of course retrofitted. The BYD vehicles with aircon also have opening windows, locked I think?

It's easier to have aircon on electrics because heating is generally via a heat pump, and aircon just involves in effect running that in reverse - as long as it's air to air rather than air to water it will generally do both.

 

[Mikey C]

Obviously passengers will open the windows on a hot day if
a) they can
b) there are no notices and announcements saying that the bus has aircon, and the windows should be kept shut.

I've never seen any TfL statements that some new buses have aircon.

Just straying off topic to answer this - not possible on high speed and many other trains, eg Pedolinos, Eurostar, IETs etc because they're pressurised to eliminate the uncomfortable pressure waves in tunnels.

In any case I'm not aware of any current UK buses with no opening windows. There were some in the 60s and 70s when there were experiments with various pressure ventilation systems.

Electrostars do have a small number of (locked) openable windows, I don't think any other "modern" trains have this option.

 

[Goldfish62]

Obviously passengers will open the windows on a hot day if
a) they can
b) there are no notices and announcements saying that the bus has aircon, and the windows should be kept shut.

I've never seen any TfL statements that some new buses have aircon.

They've regularly over the years put out statements that buses have air cooling systems (even though anyone who travels on such buses know they're often totally ineffective). The ones with full aircon are still so relatively sparse on the network that I don't think it would be a good idea advertising the fact that only a very small of the network has air conditioned buses.

Electrostars do have a small number of (locked) openable windows, I don't think any other "modern" trains have this option.

That's correct, and they're not pressurised given the relatively low speeds they travel at. Their successors, the Aventras, don't have lockable emergency hoppers.

 

[TheGrandWazoo]

Yes, always has been and probably always will be!

Indeed, and provincial operators (often with lower headways) will take the view of saying that as long as the vehicle is legal and roadworthy, then delivering against the timetable is the absolute priority.

I know you know this already but anyone can specify air-con and it comes at a cost. It costs more in capital, more in servicing, and with diesel vehicles more pointedly, it costs more to run. This is built into the tender cost. For provincial operators, those costs have never been squared with the potential financial benefits. With EVs coming in, that equation is changing.

 

[Mikey C]

They've regularly over the years put out statements that buses have air cooling systems (even though anyone who travels on such buses know they're often totally ineffective). The ones with full aircon are still so relatively sparse on the network that I don't think it would be a good idea advertising the fact that only a very small of the network has air conditioned buses.

I genuinely didn't know, until reading this thread, that ANY standard buses in London had proper aircon. Surely there should be notices inside the bus at least?

 

[Goldfish62]

I genuinely didn't know, until reading this thread, that ANY standard buses in London had proper aircon. Surely there should be notices inside the bus at least?

The BYDs have.

Why put notices the buses? They're cold inside, that's all that matters. My local air conditioned trains don't have notices.

 

[joieman]

In any case I'm not aware of any current UK buses with no opening windows. There were some in the 60s and 70s when there were experiments with various pressure ventilation systems.

The only ones I have ever known of are the Borismasters, on which they were of course retrofitted. The BYD vehicles with aircon also have opening windows, locked I think?

Diamond East Midlands' Custom Denning Element 2 electric buses (imported from Australia and entered service last year) don't have opening windows either.

Even then, there are quite a few buses that wind up with only a few opening windows: for instance, Kinchbus's new Yutong E12s only have two openings windows (apart from the one in the driver's cab). (I read two similar reports from passengers who rode them on the service 9 to Nottingham from Loughborough: the outbound journey was nice and comfortable, but the return journey was unpleasantly warm.)

 

[johncrossley]

Looking at pictures of the latest VDL and Hess electric buses (some of the popular makes in neighbouring countries), I can't see opening windows. Maybe they use a roof hatch for emergency ventilation.

 

[Goldfish62]

Looking at pictures of the latest VDL and Hess electric buses (some of the popular makes in neighbouring countries), I can't see opening windows. Maybe they use a roof hatch for emergency ventilation.

Continental buses often don't have emergency hoppers, but then aircon has largely been a standard fitment on them for a long time.

 

[johncrossley]

Continental buses often don't have emergency hoppers, but then aircon has largely been a standard fitment on them for a long time.

So if the same pattern follows in the UK, British operators will eventually be sufficiently used to air conditioning so that the fear of it not working will be a thing of the past.

 

[RJ]

In any case I'm not aware of any current UK buses with no opening windows. There were some in the 60s and 70s when there were experiments with various pressure ventilation systems.

I’ve got a Volvo decker in my fleet which has no hoppers at all and the aircon is very effective.

 

[Goldfish62]

I’ve got a Volvo decker in my fleet which has no hoppers at all and the aircon is very effective.

Bus used on local bus work?

 

[Mikey C]

The BYDs have.

Why put notices the buses? They're cold inside, that's all that matters. My local air conditioned trains don't have notices.

Your local trains don't have windows that can be opened by passengers. And especially if all the trains on the route have aircon, people will be used to them.

As the BYD double deckers will look the same to most passengers as the 95-99% of London buses without aircon, it's hardly surprising that people won't be expecting aircon.

 

[TheGrandWazoo]

Your local trains don't have windows that can be opened by passengers. And especially if all the trains on the route have aircon, people will be used to them.

As the BYD double deckers will look the same to most passengers as the 95-99% of London buses without aircon, it's hardly surprising that people won't be expecting aircon.

I guess my thought would be if someone gets on a nice cool decker, would they be looking to open the windows anyway?

I was quite impressed by that aspect of the BYDs that I experienced a few weeks ago (on quite a warm day)

So if the same pattern follows in the UK, British operators will eventually be sufficiently used to air conditioning so that the fear of it not working will be a thing of the past.

The issue has been when vehicles are cascaded to provincial fleets. With EVs, it will be less of an issue.

 

[RJ]

Bus used on local bus work?

It had done for about 18 years, but needs some brake tests before I can do that. In any case I don’t run any service routes so it wouldn’t be used for that

 

[Goldfish62]

It had done for about 18 years, but needs some brake tests before I can do that. In any case I don’t run any service routes so it wouldn’t be used for that

I'm intrigued. What bodywork does it have?

 

[RJ]

I'm intrigued. What bodywork does it have?

Wrightbus Explorer. Based on the Gemini 1 but designed with aircon in mind.

 

[MCR247]

Even then, there are quite a few buses that wind up with only a few opening windows: for instance, Kinchbus's new Yutong E12s only have two openings windows (apart from the one in the driver's cab). (I read two similar reports from passengers who rode them on the service 9 to Nottingham from Loughborough: the outbound journey was nice and comfortable, but the return journey was unpleasantly warm.)

That must be down to operators choice though as NCTs have four - two on each side

 

[RJ]

I have a suspicion that Mercedes may have fitted aircon effectively as standard since it seems to have been so in continental europe at the time and it is a fairly standard integral model (whilst UK manufacturers standard spec would omit as the UK didn't traditionally need it) but there is also the factor that whilst the model may have been designed as an urban model in Europe many of the UK customers were deploying them on more interurban cycles (except those buying artics), and tended to be operators aiming for a up market image which aircon exemplified even if not valued as such, so the proportion of time spent with doors closed is higher than purely urban cycles (this is a bit of a sweeping statement and there will always be the exception to prove the rule but a higher proportion of the buyers I can think of for the rigids sit one side and not the other).

I’ve done a bit more digging. At least two of the ex London ones I have do have the aircon pod and condenser moulds but were specced with bits inside them missing - the axial fans for a start. They have bits on the roof that the full aircon fitted ones don’t - a pair of motorised sunroof flaps which the driver can set to open in three different positions and a ventilator fan unit. There is enough equipment in the roof for driver aircon and the radial blowers do work for saloon heating as there are heat exchangers up there somewhere.

I was looking at activating the aircon by swapping out the small Konvekta cab aircon compressor it came with with a proper Bock FKX40 / 560k unit, but there’s quite a bit of work to be done. The compressor needs accessories - a clutch and electromagnetic coil. It needs a bracket to sit on, pipes for suction and delivery and probably a load of bits to go in the pod.

I’ve been researching the UK Euro 6 O295 Citaros to find out what setup they have. I had to go a fair way back through the chassis list to find one that actually has aircon and it has the same Bock/Danfoss compressor. With a paucity of Euro 6 Citaros on the market I’ve been looking at getting one made up, the price of adding aircon is around £14k. With the price of even a base model set way higher than an equivalent sized ADL or Volvo bus, plus the negative impact on MPG I can understand why the few being ordered have flat roofs.

I’ve got another Citaro (new to Go North East) which is fitted with full aircon languishing in storage but it’s too big a job to have the pod and gubbins taken off that one.

 

[Taunton]

When I was in Los Angeles in the 1980s all the buses were air con, including the remaining GM "Old Look" from the 1950s, which were still running all-day services, stopping and opening doors very frequently. I never experienced one not working. The two manufacturers, seemingly half the fleet each, were Carrier and Thermo King, notable since the GM corporation overall owned the third mainstream USA air con manufacturer, Frigidaire.

Originally powered by a separate small engine, probably a retro-fit, but they moved over to drive from the engine.

 

[Definiteness]

Obviously passengers will open the windows on a hot day if
a) they can
b) there are no notices and announcements saying that the bus has aircon, and the windows should be kept shut.

I've never seen any TfL statements that some new buses have aircon.


Electrostars do have a small number of (locked) openable windows, I don't think any other "modern" trains have this option.

The Ie Trams on the 358 have proper AC, locked windows...and exactly the kind of notices being discussed!

 

[Megafuss]

Really easy way for Mr Khan to solve this...enforce your own contract management. They spec the buses!