Effective methods of reducing bus bunching on high-frequency routes

[PTR 444]

One of the biggest challenges in planning and operating a high-frequency route is preventing buses bunching, or in other words getting too close to one another. It’s a common occurrence, most often caused by one of the buses running late, which means it picks up more passengers than intended as those passengers were meant to catch the next bus. This in turn makes the bus even more late and continues a vicious cycle of late running > extra passengers to pick up, until the bus behind catches up with it, having been sped up by fewer passengers to pick up.

Once two (or three, four, or more) buses have bunched, there is no easy way to unbunch them as the buses will keep constantly overtaking each other as they alternate between stops to pick up passengers. Even so, I am aware of a couple of methods which could help prevent this endless spiral of bunching:

The first is to send an empty bus partway along the route and pick up service from a specific point. This can work depending on the speed and congestion of nearby roads, but in many cases it rarely closes the gap in the route’s headway. An example of this was when Barrack Road in Christchurch was closed last Friday due to a serious accident. The 15-minute headway 1a route was diverted via The Grove and Fairmile Road, but with few alternative routes in the area, the area was gridlocked. Morebus’s bus tracker showed no buses at the eastern end of the route, and a bus running fast along the A338 Wessex Way, which I presume was to close the gap in headway. Even so, the sheer volume of traffic meant there were still two buses bunched at once and a 30 minute gap between them.

The second is to do what London does and hold buses at a stop for a few minutes if they are catching up with the bus in front. This works to keep headways on track but at an inconvenience to passengers who have to face slower journey times, and also does nothing to close the gap created ahead of the delayed bus.

I wonder if there are more effective ways of keeping bus route headways to form, such as allowing fast running or skip-stopping of buses that get delayed or end up bunched.

 

[Dai Corner]

One tactic is to terminate a journey short, transfer any passengers and send the bus back in the opposite direction. Another is to stop to set down only.

 

[PTR 444]

One tactic is to terminate a journey short, transfer any passengers and send the bus back in the opposite direction.

Would only really work if the bus is empty, or at a push if passengers are willing to transfer.

Another is to stop to set down only.

This is probably a better idea although the dwell time might still cause problems if a high volume of passengers are alighting. Also how would you advertise on the front that people cannot board the bus? “Sorry Bus Full”?

 

[Dai Corner]

Would only really work if the bus is empty, or at a push if there is another one right behind it and passengers are happy to transfer.

I believe this is done quite a lot in London. If the buses are bunched there will be one right behind.

This is probably a better idea although the dwell time might still cause problems if a high volume of passengers are alighting. Also how would you advertise on the front that people cannot board the bus? “Sorry Bus Full”?

Or just blank the destination. Ideally, if the technology is available, put something like "Next 4 to Town Centre 6 minutes"

 

[Llandudno]

Not so much of an issue outside of London these days as frequencies have been cut on many routes so bunching less likely to occur…!

 

[edwin_m]

Pre-purchase of tickets and dual-door buses reduce bunching, because a bus that picks up more passengers doesn't spend as much extra time at stops.

 

[RT4038]

Not so much of an issue outside of London these days as frequencies have been cut on many routes so bunching less likely to occur…!

And even if there was such a frequency, there are no (or insufficient) controller staff to make the appropriate decisions and contact drivers!

 

[Peter Sarf]

Would only really work if the bus is empty, or at a push if there is another one right behind it and passengers are willing to transfer.

This is probably a better idea although the dwell time might still cause problems if a high volume of passengers are alighting. Also how would you advertise on the front that people cannot board the bus? “Sorry Bus Full”?

Guaranteed to be a bus right behind in the context of this thread.

Yes it as happened often enough to me in London/Croydon. There is always a bus right behind or about to appear behind.

Pre-purchase of tickets and dual-door buses reduce bunching, because a bus that picks up more passengers doesn't spend as much extra time at stops.

This prompts something I have noticed in London. For years everyone as been using smart cards (Oyster or contactless) cash is no longer accepted. This has, as you say, speeded up boarding dramatically. But there is nowadays often a delay caused by someone trying to pay with their mobile app - either the app is not ready or there is some other problem. What is the problem with theses phones? This is becoming a lot more of an issue than people who get on the bus and then look for their Oyster card.

The above and the occasional battle of the wheelchair taking priority over an obstinate child push chair owner are the two causes of delay I see most often at my end of the route. Both should be avoidable but roadworks are another issue.

Another feature of the bunching is that this is often hard to solve until after the rush "hour". I know that leaving home around 18:00 is a good time to see this bunching in one direction and a growing gap in the direction I want to travel !.

 

[Magdalia]

Busway route A in Cambridge still bunches on a 20 minute frequency. With single entrance single deck buses there can be very long dwell times at busy stops, notably the railway station and Addenbrookes outpatients.

 

[Peter Sarf]

Busway route A in Cambridge still bunches on a 20 minute frequency. With single entrance single deck buses there can be very long dwell times at busy stops, notably the railway station and Addenbrookes outpatients.

I can imagine Addenbrookes generating a lot of passengers with mobility issues. Perhaps more slack in the timetable for that stop. But then I fear the times of day affected is not predictable.

For the train station commuting periods will be more predictable. But I suspect the timetable is clockface and therefore assumes the same journey time and stop times all day - unrealistic planning ?.

 

[Bletchleyite]

The best one, but not one operators seem willing to do outside London, is to change ticketing and vehicle design to reduce dwell at stops to an absolute minimum. The problem is basically caused by a delayed bus being slowed down more and more because more passengers are waiting for it, and each needs to conduct a transaction with the driver taking at least 10-20 seconds, plus the time taken waiting for people to alight.

If you can get stop times down to the time it takes for people to board without breaking step, as is possible if you use a combination of contactless and smartcards (not barcodes, they are slower), then the effect is reduced, and if you fit rear doors for exit you reduce it a little more on routes where people often board and alight at the same stop. I certainly notice a lot less bunching in London.

You don't get bunching on frequent tram services, and the reason why is obvious - even if 50 people are standing on the platform, boarding and alighting takes under a minute. Boarding 50 people onto a bus operated in the normal provincial UK manner will take well over 10 minutes.

This prompts something I have noticed in London. For years everyone as been using smart cards (Oyster or contactless) cash is no longer accepted. This has, as you say, speeded up boarding dramatically. But there is nowadays often a delay caused by someone trying to pay with their mobile app - either the app is not ready or there is some other problem. What is the problem with theses phones? This is becoming a lot more of an issue than people who get on the bus and then look for their Oyster card.

This is indeed a problem to the point that I use a physical card for London services rather than a phone. Apple is said to have introduced a transit mode that doesn't require the phone to be unlocked to pay, but last time I tried it it didn't work. I don't think Android has anything. I am inclined to say if I was an operator I would say no phone payments for now until this is solved, as while it doesn't take as long as paying cash and giving change after a discussion about "er, the stop after where the Dog and Duck used to be, yeah, a bit before Tesco, mate"* ** it is causing a noticeable problem.

With Android I think one issue is that some phones have face unlock which isn't as secure as Apple's (unlike Apple it could be unlocked using a photograph of the user) and so can't be used to verify card payment. Thus people think their phone is unlocked when it isn't, and are confused as to why.

* Germany gives recognisable and well publicised names to stops, maybe we should?

** Now we have the £2 thing, going flat fare would help. "Two quid mate" while chucking the coins in the tray is much quicker than staged pricing. I did find this quite noticeable when I moved from Manchester to Milton Keynes, where a simple "40 please" or "60 please" on the student routes was much quicker, both in terms of the actual transaction and people knowing what the fares were and thus having correct change ready.

 

[Llandudno]

The best one, but not one operators seem willing to do outside London, is to change ticketing and vehicle design to reduce dwell at stops to an absolute minimum. The problem is basically caused by a delayed bus being slowed down more and more because more passengers are waiting for it, and each needs to conduct a transaction with the driver taking at least 10-20 seconds, plus the time taken waiting for people to alight.

If you can get stop times down to the time it takes for people to board without breaking step, as is possible if you use a combination of contactless and smartcards (not barcodes, they are slower), then the effect is reduced, and if you fit rear doors for exit you reduce it a little more on routes where people often board and alight at the same stop. I certainly notice a lot less bunching in London.

You don't get bunching on frequent tram services, and the reason why is obvious - even if 50 people are standing on the platform, boarding and alighting takes under a minute. Boarding 50 people onto a bus operated in the normal provincial UK manner will take well over 10 minutes.



This is indeed a problem to the point that I use a physical card for London services rather than a phone. Apple is said to have introduced a transit mode that doesn't require the phone to be unlocked to pay, but last time I tried it it didn't work. I don't think Android has anything. I am inclined to say if I was an operator I would say no phone payments for now until this is solved, as while it doesn't take as long as paying cash and giving change after a discussion about "er, the stop after where the Dog and Duck used to be, yeah, a bit before Tesco, mate"* ** it is causing a noticeable problem.

With Android I think one issue is that some phones have face unlock which isn't as secure as Apple's (unlike Apple it could be unlocked using a photograph of the user) and so can't be used to verify card payment. Thus people think their phone is unlocked when it isn't, and are confused as to why.

* Germany gives recognisable and well publicised names to stops, maybe we should?

** Now we have the £2 thing, going flat fare would help. "Two quid mate" while chucking the coins in the tray is much quicker than staged pricing. I did find this quite noticeable when I moved from Manchester to Milton Keynes, where a simple "40 please" or "60 please" on the student routes was much quicker, both in terms of the actual transaction and people knowing what the fares were and thus having correct change ready.

Used to be an unofficial flat fare in Kirkby, Merseyside quite a few years ago.

Punter would slap 10p in the drivers tray and say ‘You’re alright mate!’

Certainly speeded up dwell times…!

 

[Magdalia]

Not so much of an issue outside of London these days as frequencies have been cut on many routes so bunching less likely to occur…!

That one should have been quoted in my previous message!

** Now we have the £2 thing, going flat fare would help. "Two quid mate" while chucking the coins in the tray is much quicker than staged pricing. I did find this quite noticeable when I moved from Manchester to Milton Keynes, where a simple "40 please" or "60 please" on the student routes was much quicker, both in terms of the actual transaction and people knowing what the fares were and thus having correct change ready.

In Cambridge Stagecoach has a partial version of this, that has the most impact on the busiest stops. Fares Station-City Centre, Station-Hospital and City Centre-Hospital are all £1. I keep a pot of £1 coins for these journeys, paying £1 in cash is very quick.

 

[Busaholic]

This prompts something I have noticed in London. For years everyone as been using smart cards (Oyster or contactless) cash is no longer accepted. This has, as you say, speeded up boarding dramatically. But there is nowadays often a delay caused by someone trying to pay with their mobile app - either the app is not ready or there is some other problem. What is the problem with theses phones? This is becoming a lot more of an issue than people who get on the bus and then look for their Oyster card.

The above and the occasional battle of the wheelchair taking priority over an obstinate child push chair owner are the two causes of delay I see most often at my end of the route. Both should be avoidable but roadworks are another issue.

Another feature of the bunching is that this is often hard to solve until after the rush "hour". I know that leaving home around 18:00 is a good time to see this bunching in one direction and a growing gap in the direction I want to travel !.

Too long since I last travelled on a bus in London, owing to my infirmity, but these mobile apps are causing delays bordering on closedowns in many areas, five minutes at at a supermarket check-out here, ten, even fifteen minutes once, at a couple of Costa Coffees I frequent. In every case I've come across, no apology is ever forthcoming from the customer to the rest of the queue. These things have just become too clever by half (irony intended) for their own good, and we need to return to simpler methods like, as you say, an actual physical Oyster card.

Regarding the problem of bunching, it is never one that will be truly 'solved' in any setting, except perhaps in a totalitarian society: personally, I'd choose bunching over that. I had to write a dissertation on bus bunching prior to being accepted by London Transport as (it turned out) the first person on their Traffic Administration training scheme in 1970/1, as the Bus Schedules Dept. had proved beyond my capabilities and interest, but they must have thought I showed some sort of promise. I've no idea what I churned out (double deck one person operation was about to commence in Inner London) but I certainly gave it much thinking. One thing I would never countenance would be sudden skipping of stops, either on bus, tube or train, except in genuinely emergency situations. Of course, fifty years ago L.T. ran the buses themselves and the busworkers' union was very powerful and inflexible, though I can understand why some of those inflexibilities existed.

 

[WM Bus]

I believe this is done quite a lot in London. If the buses are bunched there will be one right behind.

Or just blank the destination. Ideally, if the technology is available, put something like "Next 4 to Town Centre 6 minutes"

I was on a late running Diamond Streetlite recently. The driver had 94E Ward End on the destination leaving City Centre and it was 40 or so minutes down. Any remaining passengers on board were turfed off at Fox & Goose to get the next bus and the bus turned round to head back to City.
On the same route I've heard National Express drivers being told to transfer passengers onto the bus behind when they get to the Fox and Goose over their radio.

 

[Spsf3232]

From my experience of driving, it's a hard one to sort out without someone taking a bit of thought to the task. Unfortunately this is very much lacking these days with management or drivers who are not allowed to think for themselves any more.

The best official way I've come across that seemed to work pretty well was at First Glasgow back in late 2000s when frequent routes like the 9 and 62 through the west end didn't have a timetable. Drivers were given a departure time from the terminal and off they went. Along the route there were controllers who would monitor the times of the buses, holding any that were close to the one in front or taking it out of service to catch up when the bus behind was in sight. It worked pretty well and the frequency tended to be kept no matter what the traffic was like. When it was quiet you would have about 30 minutes layover which gave plenty to spare if needed for when things go wrong.

Now we find that the frequency has been cut to the minimum, the buses are busier, slower to load due to ticket machines, door interlocks and stop start technology that all add valuable seconds to the journey. Traffic is now busier than it ever was and it seems like traffic lights now take longer to change! Then the layover itself has been cut to sometimes minutes meaning delays just spiral out of control.

The driver is now out on the road on his own, with no on street staff, no radio control and contact is done via message on Ticketer on which you have more chance of winning the lottery than getting a response!

All that said, until the bus industry has enough drivers to restore normal basic working nothing will be done and only then if that problem is solved we might find a management team willing enough to try and solve the problems at hand rather than just do the bare minimum to keep the lights on until they retire

 

[Dai Corner]

The driver is now out on the road on his own, no on street staff, no radio control, contact is done via message on ticketer which you have more chance of winning the lottery than getting a response!

Though the technology means a single controller could sit in the office and see at a glance where all the buses were, where there is congestion, and send messages to drivers to wait, go out of service or whatever was needed.

 

[Geordie driver]

One wonders where this spare driver is coming from to break up the bunching, given that most companies don't have enough drivers to cover the runs they are supposed to operate.

We were told to just keep going, they were worried about lost mileage being reported to the traffic commissioner, this was when the traffic commissioner was a force to be reckoned with, not the toothless tiger it is now.

At one time if you had 3 buses running together on the same route, passengers would be transfered to the bus running on time and the other 2 would run light to a place where they could start picking up on time. Best possible solution and common sense. This was all organized by the drivers, no radios were fitted and there would be no supervisor visible.

There was also a feeling at the time of getting the job done with the best outcome for the passengers, a bit of pride in the service you delivered.

The company put a notice up telling us to just keep going and not to use common sense. This was the actual wording of the notice.

I once had an inspector try to book me for running 5 minutes early, I wasn't, I was 55 minutes late. He then told me to wait my time and start running at the correct time for my next run, I refused as we had been told never to do that. Do not use common sense.

Small wonder the industry is in a mess.

 

[SSmith2009]

my local services are terrible for bunching and the operator has recently introduced a new timetable with peak time buses getting around 40 to 50 mins each way while off peak they get 30 to 35 each way, this change seems to have helped.

although the peak frequency is reduced to every 15 mins compared to every 12 during the off peak.

 

[Busaholic]

my local services are terrible for bunching and the operator has recently introduced a new timetable with peak time buses getting around 40 to 50 mins each way while off peak they get 30 to 35 each way, this change seems to have helped.

although the peak frequency is reduced to every 15 mins compared to every 12 during the off peak.

The latter makes sense if it cuts out the bunching and makes it more reliable. I think in all honesty we have to stop thinking so much in terms of there being a standard peak time on each individual route, on some there will be no obvious one and on others an extra journey, perhaps a 'short' operating only in one direction, will suffice.

 

[Bletchleyite]

The latter makes sense if it cuts out the bunching and makes it more reliable. I think in all honesty we have to stop thinking so much in terms of there being a standard peak time on each individual route, on some there will be no obvious one and on others an extra journey, perhaps a 'short' operating only in one direction, will suffice.

I'm all for clockface timetables and a big proponent of them on the railway, but it's telling that the countries that do buses well (e.g. the Netherlands and Germany) pretty much never do this - the peaks are near enough always different. Even if you have perfect infrastructure and frictionless boarding with three sets of doors, you still run slower when there are more passengers.

Bunching is started when a bus runs late, and gets worse because it then picks up more passengers (because on high frequency routes people show up at stops pretty randomly). If you avoid that in the first place, you've made a good start.

 

[Busaholic]

I'm all for clockface timetables and a big proponent of them on the railway, but it's telling that the countries that do buses well (e.g. the Netherlands and Germany) pretty much never do this - the peaks are near enough always different. Even if you have perfect infrastructure and frictionless boarding with three sets of doors, you still run slower when there are more passengers.

Bunching is started when a bus runs late, and gets worse because it then picks up more passengers (because on high frequency routes people show up at stops pretty randomly). If you avoid that in the first place, you've made a good start.

I don't think you understood my post. I was suggesting there is evidence that in London, and maybe other cities, that old-style peaks in passenger numbers are much diminished, whether owing to office workers in particular not returning to their previous routine, the jobs in coffee shops/bars/restaurants that depended on those workers being lost in consequence, lack of tourists, etc. From all I have read, no other European city has been affected to the same degree. Then add the shortage of bus drivers, and those extra buses in the peaks are the first that a bus company might feel could be cut without too drastic an effect: in any case 'spreadover' duties are the least generally popular among drivers.

Clockface timetables in Central London, and much of Inner London, might appeal to accountant types, but would be a work of fiction. There is much more of a case for them in Outer London. If the number of buses allocated to a route during daytime was capable of providing a theoretical 13 minute interval, whereas it was actually showing a 15 minute interval 'for neatness', I'd say that was an opportunity missed to provide a better service without cost, and I'm sure most passengers in London would agree with me.

 

[Bletchleyite]

Clockface timetables in Central London, and much of Inner London, might appeal to accountant types, but would be a work of fiction. There is much more of a case for them in Outer London. If the number of buses allocated to a route during daytime was capable of providing a theoretical 13 minute interval, whereas it was actually showing a 15 minute interval 'for neatness', I'd say that was an opportunity missed to provide a better service without cost, and I'm sure most passengers in London would agree with me.

While this is a slightly different discussion, I would say you have to get to 6 buses per hour or better before there is sense in that. For a 4 bus per hour service, unless you like standing in the cold/rain memorable times are more useful. Yes, you can use your phone to see real time departures, but remember a lot of bus users are not smartphone users. My personal view is that even Manchester Metrolink's 12 minute frequency is insufficient for true "turn up and go" - to me the tipping point is definitely every ten minutes.

And of course there's punctuality. A punctual 4 bus per hour service is better than an unpunctual 5 bus per hour one, and will bunch less. As I mentioned the root cause of bunching is the way a delayed bus will pick up more passengers than one that is on time so gets later and later, because it'll start picking up people who would otherwise have got the next one. If you operate a punctual, reliable service with long enough layovers at both ends and enough mid-route padding even things like taking staged cash fares won't *cause* bunching unless you randomly get a high number of passengers showing up at one stop unexpectedly. They just make it worse when a delay or cancellation has occurred.

 

[Simon75]

A few years ago the 3 bus Hanley to Crewe extended in Crewe to Leighton Hospital.
As the bus was late, driver, whilst at Crewe bus station, rang the garage to ask if he could not drive to Leighton Hospital, but continue back to Hanley, which he did

 

[asb]

A risk for those who want to go to the end of any bus route, or railway line, where a turning point exists before the terminus, as the Controller focuses on getting the driver(s) back on time, and potentially forgets those living at the extremity.

 

[markymark2000]

Having depot staff who are willing to let you drop trips though I would say is a key issue. I've known routes with 3 buses bunching but the depot say 'keep running, you will catch up' because they don't want the paperwork of cutting the trip when in reality, if they said 'drop that trip and run your next one on time' means that you would sit at the bus station for 10 minutes and be back on time.


The solutions in my opinion depend on the route but ideally, I would always say that it's important to try and keep the bus open to passengers as much as possible and reduce dead running. As soon as a bus is running dead or short turned, the next bus picks up 2 lots of passengers and then that becomes delayed and regulating the service then becomes a never ending challenge.

For a number of routes, I would say if there is a diversion that can be taken, where minimal passengers are affected but there is a time benefit for the bus to not serve the area, that should be undertaken. Something like Liverpool to Speke buses, run the bus fast along Speke Boulevard into Morrisons, switch the machine and everything over to 'Towards Liverpool' and then serve the estate towards Liverpool so anyone already on the bus can still alight at their stop without issue and anyone heading towards Liverpool is unaffected. This would save 6 minutes. Plus the supposed layover time, that has the potential to catch up a bit of time.

Most high frequency corridors are suitable for set down only so as soon as you're in an area which is suitable and preferably past a busy stop/area, a set down only on the front bus means that, again, anyone already on the bus is ok and it keeps as many people moving as possible.

If there are multiple buses following eachother on the same route, you need to ensure at least every other one does the full journey so as the extreme ends of the route have some kind of service and then sort them buses out on as they head in the other direction.

Strategic spares could help to stop bunching on more local routes. In many towns/cities for example, there is no 'strategic spare' bus in the city so any delays have to keep going on and as each driver changeover happens, the buses have to just keep being late until eventually a trip gets dropped but a strategic spare would mean a changeover driver would take the spare and run on time. The current driver would then drop the bus in the bus station and that bus then becomes the strategic spare.

Noting the theme? Keeping as many people moving as possible, keeping the bus on route for the most amount of time and trying to avoid kicking people off the bus but at the same time, ensuring the bus can catch up time without telling them to keep plodding on all day ignoring the basics that you can't unbunch buses without stupid amounts of layover or making changes to how the bus is operating.


Of course putting people onto the bus behind works but generally this delays the bus more, upsets the passengers more, risks overcrowding the bus behind and that then upsets the passengers behind too so ideally, the amount of people being switched over should be minimal. Such as if the route does a double run or near double run, just transfer over passengers who would alight on the affected section (thinking like Manchester 38, the bus could cut Little Hulton and remain on Manchester Road).

 

[daodao]

Not so much of an issue outside of London these days as frequencies have been cut on many routes so bunching less likely to occur…!

Exactly. There are few if any in rural areas such as Cheshire, or even in smaller conurbations such as the Potteries. There are only a few main roads in Greater Manchester that I can think of with a bus at least every 5 minutes:

• the Oxford Road/Wilmslow Road corridor as far south as Withington (where Palatine Road diverges)
• route 192 from Manchester Piccadilly as far south as Stepping Hill Hospital
• Rochdale Road as far north as Middleton, but co-ordination here would be difficult at present as there are several different operators.

There is of course tram bunching in Manchester from Trafford Bar northwards into central Manchester.

 

[Bantamzen]

Exactly. There are few if any in rural areas such as Cheshire, or even in smaller conurbations such as the Potteries. There are only a few main roads in Greater Manchester that I can think of with a bus at least every 5 minutes:

• the Oxford Road/Wilmslow Road corridor as far south as Withington (Red Lion)
• route 192 from Manchester Piccadilly as far south as Stepping Hill Hospital
• Rochdale Road as far north as Middleton, but co-ordination here would be difficult at present as there are several different operators.

There is of course tram bunching in Manchester from Trafford Bar northwards into central Manchester.

Even where bunching can occur, what realistically can be done to prevent it? There are so many factors that can create this effect from passenger boarding, presenting / paying for tickets, enquiries about the route to the driver etc. And there are external factors such as traffic density & flows. Sure some level of improving boarding times, especially around ticketing can help a bit, but at the end of a day a bus in front picking up a higher density of passengers than the bus behind is potentially going to get caught up. Putting operationally convenient mitigations such as terminating short, stopping picking up passengers where capacity is still available, diverting to avoid passengers and even reducing frequencies to reduce the chance of bunching might please the pen pushers, it won't please the paying punters.

 

[M803UYA]

Having depot staff who are willing to let you drop trips though I would say is a key issue. I've known routes with 3 buses bunching but the depot say 'keep running, you will catch up' because they don't want the paperwork of cutting the trip when in reality, if they said 'drop that trip and run your next one on time' means that you would sit at the bus station for 10 minutes and be back on time.

Unsure how the 'modern' method of operations works, but lost mileage is something measured internally - i.e: reasons must be given for lost trips and it's always one item on a monthly meeting with the senior management in a large bus operation. If that figure is 'high' then it's discussed and possibly action taken. Somewhere like Stagecoach that would mean a manager relieved of their duties and redeployment....
So having control staff being inflexible is one possible symptom - it comes from depot management not wanting to lose mileage. Some will be better than others at management but you'll get that in all walks of life.

 

[Bletchleyite]

There is of course tram bunching in Manchester from Trafford Bar northwards into central Manchester.

To what extent? Trams should in theory bunch less because boarding and alighting takes seconds.