What are service numbers for?

[Rhydgaled]

So, we've established that the 554 is very much a separate route.

Yes, it is a seperate route from the X50, but I think it really is at least two seperate routes by itself.

So then the X50.... Yes there's the two journeys you mention. Do they justify a separate number? Possibly? However CCC have probably viewed that there's enough commonality to put them under the X50 number. Would be people be more confused by having an X50/X51/X52 to reflect the different variations when the majority of route and by extension passengers are only interested in the main common portion of route?
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Pet hate of mine is route numbers that use the prefix X but stop at every stop, X30 Chester-Warrington prime example, prefix X is normally used for express route.

Not necessarily. What was Wilts & Dorset use X to signify cross country.

I don't have an issue with X being used as something other than a balls out express, as long as it's a faster variant of another service. However, there were some in North Somerset that were simply renumbered into an X series but are full stoppers. Meanwhile other X services are express versions. :roll:

Up until about a year ago (when Arriva left the area), the X50 wasn't the only number. X50 was the faster variant, being the direct route avoiding New Quay (which was more frequent than now). The services via both New Quay and Aberporth were 550 (although things got a bit confusing towards the end because of the Richards/Arriva boundary, but I won't go into that here). There was still confusion, because there were a handful of workings which did New Quay or Aberporth but not both, which were allocated either X50 or 550 seemingly at random, but for the most part it was just the two routes and things were much clearer than today's "everything between Cardigan and Aberaeron is an X50" policy.

 

[Statto]

Cheltenham - mentioned both further up this thread.
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Not necessarily. What was Wilts & Dorset use X to signify cross country.

I don't have an issue with X being used as something other than a balls out express, as long as it's a faster variant of another service. However, there were some in North Somerset that were simply renumbered into an X series but are full stoppers. Meanwhile other X services are express versions. :roll:

I can see the logic in X being CrossCountry, but i hate it when X routes use all stops on the route, X30 Chester-Warrington being an example which used to be C30 yet same depot operates X1 which is an express route.

Some companies don't use X for express routes, NBC company Crosville used to use L meaning Limited Stop, West Midlands Travel used 9** for express routes

 

[TheGrandWazoo]

I can see the logic in X being CrossCountry, but i hate it when X routes use all stops on the route, X30 Chester-Warrington being an example which used to be C30 yet same depot operates X1 which is an express route.

Some companies don't use X for express routes, NBC company Crosville used to use L meaning Limited Stop, West Midlands Travel used 9** for express routes

In the mid 80s, United had a habit of X prefixes for limited stops (e.g. X5 and X55 Hartlepool to Newcastle) but also suffixes in a few cases (23X Hartlepool to Sunderland).

United also numbered many of their schools services with 8** numbers

 

[dvboy]

National Express West Midlands use 900 series routes for the Sutton Lines. The 902, 904, 905, 907, 914 and 915 all spring to mind, as well as the 934, 935, 952 and 997.

There is also the 104, 105 and 115 too, which I believe is the 'slower' variant, unless there have been changes in the route since.

Some of those numbers don't exist any more but generally the 902, 904, 905, 914 use the Aston Expressway while the 115 uses Lichfield Road. 907 is Sutton via Perry Barr. 934, 935, 952 and 997 aren't Sutton lines but all go via Perry Barr and I think are all limited stop. The X51, also limited stop, goes via Perry Barr and goes against this numbering pattern.

Centro have duplicated some route numbers across the West Midlands whereby there are four routes numbered 5 for example - this is fine on the ground as none of them overlap, but is not so great online for example when they or bus companies are using social media or posting disruption information online they have to explain which of the 5s they are referring to. This wasn't the case up until a few years ago.

 

[bussnapperwm]

Some of those numbers don't exist any more but generally the 902, 904, 905, 914 use the Aston Expressway while the 115 uses Lichfield Road. 907 is Sutton via Perry Barr. 934, 935, 952 and 997 aren't Sutton lines but all go via Perry Barr and I think are all limited stop. The X51, also limited stop, goes via Perry Barr and goes against this numbering pattern.

Centro have duplicated some route numbers across the West Midlands whereby there are four routes numbered 5 for example - this is fine on the ground as none of them overlap, but is not so great online for example when they or bus companies are using social media or posting disruption information online they have to explain which of the 5s they are referring to. This wasn't the case up until a few years ago.

I thinks he closest routes have appeared with the same number is the NXWM 46 in Perry Barr and NXWM 46 just up the road at the Scott arms...

Also, don't forget the X prefixed routes in Centroland that are Limited stops (X51 Walsall/Cannock, X64 Woodgate and X73 once a day to Tamworth Estates)...and the X route that is all stops (X96 - in this case I think it's more eXpress as its a journey of 20 mins or less between Merry Hill and Dudley/Stourbridge even though the 276 runs a similar trip time to Dudley from Merry Hill)

Then there's the X suffex route which calls at all stops (HiRide 40X)

And the ex BMMO/Midland Red routes that call at selected stops yet neither are in the 9xx series or the Xnn series (First 144 - via Bristol Road to Worcester, Diamond 146 - via Pershore Road to Redditch and Arriva 110/116 - non stop from Gravelly Hill to City via Aston Distressway to Tamworth)

 

[Mutant Lemming]

You also get instances of one route having two numbers like the X2/2X Liverpool - Preston service. it is the X2 for some of it's journey then becomes the 2X although it is advertised as a through journey.

 

[TheGrandWazoo]

You also get instances of one route having two numbers like the X2/2X Liverpool - Preston service. it is the X2 for some of it's journey then becomes the 2X although it is advertised as a through journey.

A rare instance of Stagecoach having a through route with separate numbers to keep it under UK Domestic regs; usually they don't bother.

 

[Statto]

Some of those numbers don't exist any more but generally the 902, 904, 905, 914 use the Aston Expressway while the 115 uses Lichfield Road. 907 is Sutton via Perry Barr. 934, 935, 952 and 997 aren't Sutton lines but all go via Perry Barr and I think are all limited stop. The X51, also limited stop, goes via Perry Barr and goes against this numbering pattern.

Centro have duplicated some route numbers across the West Midlands whereby there are four routes numbered 5 for example - this is fine on the ground as none of them overlap, but is not so great online for example when they or bus companies are using social media or posting disruption information online they have to explain which of the 5s they are referring to. This wasn't the case up until a few years ago.

Routes 934, 935, 952 and 997 also 907 are part limited stop, with limited stop section Brum-Perry Barr then stop at all stops to the outer terminus.

NEWM have had a few renumberings in the last few years, Wolverhampton local numbers used to be 5** Walsall local routes 3** which have has the 5 & 3 dropped
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A rare instance of Stagecoach having a through route with separate numbers to keep it under UK Domestic regs; usually they don't bother.

It's not UK domestic regs but regs introduced by the EU, very easy to get around just by registering 2 separate services, but operating a through route, Arriva Wales do this with a couple of routes being 5 Caernarfon-Llandudno & 11 Chester-Rhyl

 

[TheGrandWazoo]

It's not UK domestic regs but regs introduced by the EU, very easy to get around just by registering 2 separate services, but operating a through route, Arriva Wales do this with a couple of routes being 5 Caernarfon-Llandudno & 11 Chester-Rhyl

No, you misread me. It's to KEEP it under UK domestic otherwise you'd have to operate it under EU drivers regs. That's why it's in two halves.

Stagecoach were the greatest exponents of that (the X4 in Northampton is registered in 3 portions!) and usually that's what Stagecoach do (2 or 3 portions registered but with one number). That's why the X2/2X is a bit odd!

 

[Wolvercoter]

Exeter City services use letters rather than numbers, is there anywhere else where letters are used?

Think Caerphilly does as well.

I moved to Exeter five years ago. Old habits die hard when I refer to my local bus as the 'number K'.

The 'X' service in Exeter is an odd one... the single outward (0525) and return journey (0556) do not follow the same route! Service 'Y' and 'Z' are equally as weird.

 

[Busaholic]

Think Caerphilly does as well.

I moved to Exeter five years ago. Old habits die hard when I refer to my local bus as the 'number K'.

The 'X' service in Exeter is an odd one... the single outward (0525) and return journey (0556) do not follow the same route! Service 'Y' and 'Z' are equally as weird.

Perhaps we'll get refinements, so a X+ and a X-, or Z* and Z**

 

[ValleyLines142]

Think Caerphilly does as well.

Caerphilly has the A, B and X. Not as many as Exeter and Cheltenham.

Also, with Exeter at least, the letters usually stand for where they are heading. For example, the A goes to Alphington and the T goes to Topsham, although admittedly not every letter matches, such as the other terminus of the A going to Thornpark Rise!

I must admit I'm not a fan of what NXWM have done with the Walsall and Wolverhampton routes. I think it was better to keep them in the 300 and 500 category respectively. Timetable searches are a bugger as a result.

 

[telstarbox]

In Manchester Stagecoach operate the X50 (Piccadilly-Trafford Centre) and 50 (East Didsbury - Salford Quays) which are completely different routes and don't even share a start or end point!

 

[Statto]

In Manchester Stagecoach operate the X50 (Piccadilly-Trafford Centre) and 50 (East Didsbury - Salford Quays) which are completely different routes and don't even share a start or end point!

Because the X50 is express version of the stopping service 250.
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Sticking with Manchester GM Buses era[not the cowboy reincarnated one] express routes where given normal numbers like 9-32-34 ecc but had vehicles allocated in a different livery with duel purpose seating.

 

[dvboy]

NEWM have had a few renumberings in the last few years, Wolverhampton local numbers used to be 5** Walsall local routes 3** which have has the 5 & 3 dropped

And Dudley 2**, although it was Centro that did this renumbering, not NXWM.

There are a few that didn't change, and still remain such as the 529, 255, 256... I think the majority of these are in Dudley.

I still hear Wolverhampton's 1 referred to by people as the "501" at bus stops.

 

[neilmc]

In Leeds tramway days, the outgoing tram from the city centre would show a route number quite different from the return journey e.g. 18 to Cross Gates might return as 26 Middleton, or something else depending on the schedules at the time. This made sense in a way, since if you were returning to town any tram would do as there were no inbound route divergences and where the tram went to NEXT was significant, the fact that it would go to the city centre first was a given.

Weirder still was the Huddersfield bus system whereby short workings had separate route numbers, so when I lived at Cowlersley I could catch 50-52 to Marsden, the occasional 53 to Slaithwaite and the even more occasional 54 to Cowlersley. I also discovered I could catch the 8 to Hill Top, with its short working 9 to Wilberlee, and told my student flatmates so who were a bit miffed with me at ending up somewhere on Crosland Moor when they tried it. Apparantly Huddersfield thought that a separate number for short workings was required, but not for a route which took alternate routings via Manchester Road or Crosland Moor where it showed the SAME number in both cases!

 

[Rhydgaled]

No it is NOT more than one route... it IS one route with more than one VARIATION.... in some parts of the UK there are services where no 2 journeys follow exactly the same route...

By what definition of route? I used the term 'service numbers' rather than 'route numbers' in the title of this topic on purpose. The two are often used interchangeably to mean the same thing, so if you are using the word 'route' in the context of the term 'route number' then what you say makes sense. However, the word 'route' by itself means:

1 A way or course taken in getting from a starting point to a destination: "the scenic route from Florence to Siena"
More example sentences Synonyms
1.1 The line of a road, path, railway, etc. "proposals have been put forward for a new route around the south of the town"

(my bold)(Source of quote). My interpretation of this definition of 'route' is that it is specific, and that a variation to one route creates a different route. To put it another way, if we are being strict about the use of the word, a route is immutable, like a number. If you have the number 'one' and you add 'two' to it, you don't change the number 'one' you get a completely different number as the result.

... and no-one seems to have problems.

I have not been using the bus as much as I used to, and despite that between Dec 2013 and Dec 2014 I have seen passengers on the wrong bus twice. Once prior to Dec 2013, when most of the 'variations' were clearly labeled with different service numbers, I saw passengers who had failed to board a service that would have taken them where they wanted to go, again because of a 'variation' as you put it.

 

[Teflon Lettuce]

By what definition of route? I used the term 'service numbers' rather than 'route numbers' in the title of this topic on purpose. The two are often used interchangeably to mean the same thing, so if you are using the word 'route' in the context of the term 'route number' then what you say makes sense. However, the word 'route' by itself meansmy bold)(Source of quote). My interpretation of this definition of 'route' is that it is specific, and that a variation to one route creates a different route. To put it another way, if we are being strict about the use of the word, a route is immutable, like a number. If you have the number 'one' and you add 'two' to it, you don't change the number 'one' you get a completely different number as the result.

I have not been using the bus as much as I used to, and despite that between Dec 2013 and Dec 2014 I have seen passengers on the wrong bus twice. Once prior to Dec 2013, when most of the 'variations' were clearly labeled with different service numbers, I saw passengers who had failed to board a service that would have taken them where they wanted to go, again because of a 'variation' as you put it.

so how do you explain how people get on the wrong bus in London where all services have one route number per route variation... with clear destination displays AND up to SIX intermediate points?

Route no service no or line no... call it what you will... what you are suggesting is something along the lines of the Bassom system that was in operation in London from 1924... where routes where given different suffix letters according to variation and/ or terminal points... leading to services using up to "G"... and where for many years no bus on route 11 ran with plain "11" as their service number... in fact the main service for many years was 11E.

Now I wonder why that system was abandoned by London Transport as soon as legislation took route numbering away from the beurocratic hands of the Metropolitan Police?

 

[Busaholic]

so how do you explain how people get on the wrong bus in London where all services have one route number per route variation... with clear destination displays AND up to SIX intermediate points?

Route no service no or line no... call it what you will... what you are suggesting is something along the lines of the Bassom system that was in operation in London from 1924... where routes where given different suffix letters according to variation and/ or terminal points... leading to services using up to "G"... and where for many years no bus on route 11 ran with plain "11" as their service number... in fact the main service for many years was 11E.

Now I wonder why that system was abandoned by London Transport as soon as legislation took route numbering away from the beurocratic hands of the Metropolitan Police?

Afraid the (up to six) intermediate points on London buses are disappearing fast, as destination only becomes the rule and not the exception. A side blind may contain a 'via' point or two, but these are sometimes of little use, a no. 6 going via Charing Cross to get the further quarter mile to Aldwych helps no-one.

 

[Teflon Lettuce]

Afraid the (up to six) intermediate points on London buses are disappearing fast, as destination only becomes the rule and not the exception. A side blind may contain a 'via' point or two, but these are sometimes of little use, a no. 6 going via Charing Cross to get the further quarter mile to Aldwych helps no-one.

Yes I was aware that this is slowly happening... however my point was that even with the clearest destination displays London has always had problems with passengers boarding the wrong bus... thus blowing Rhydgaled's argument that every route variation should have a seperate number out of the water.

 

[Tom B]

Yes I was aware that this is slowly happening... however my point was that even with the clearest destination displays London has always had problems with passengers boarding the wrong bus... thus blowing Rhydgaled's argument that every route variation should have a seperate number out of the water.

The system used by Lothian RT is better - a full route journey displays the intermediates, but if it is only part route the intermediates change to a bright pink screen and the letters "PART ROUTE".

 

[Busaholic]

The system used by Lothian RT is better - a full route journey displays the intermediates, but if it is only part route the intermediates change to a bright pink screen and the letters "PART ROUTE".

Being an old g*t I can remember the London system into the 1950s when, for instance, an 11 going to Aldwych rather than the full route to Liverpool Street would display 'ALDWYCH ONLY' all in caps but the 'only' bit would be in smaller lettering. Intermediate blinds stayed as they werte though. In cases where the Sunday route (say) was shorter or longer than the weekday route a different intermediate blind was often used.

 

[quarella]

Whatever you do, people will finish up on the wrong bus, or miss the bus they want despite all the technology now available. Online timetable, journey planners with real time service information. Bus stops with departure displays. Destination indicators listing calling points. I believe the X50/550 services Rhydgaled refers to in the Traws Cambria/Traws Cymru thread have this fitted. Even if travelling on a old fogey pass or day ticket if you are not sure, ask.

 

[Busaholic]

Whatever you do, people will finish up on the wrong bus, or miss the bus they want despite all the technology now available. Online timetable, journey planners with real time service information. Bus stops with departure displays. Destination indicators listing calling points. I believe the X50/550 services Rhydgaled refers to in the Traws Cambria/Traws Cymru thread have this fitted. Even if travelling on a old fogey pass or day ticket if you are not sure, ask.

I know more young fogeys than old ones.

 

[Rhydgaled]

Bus stops with departure displays. Destination indicators listing calling points. I believe the X50/550 services Rhydgaled refers to in the Traws Cambria/Traws Cymru thread have this fitted.

The TrawsCymru T5 (which has now largely replaced the X50/550) has LED signs at Haverfordwest bus station and Fishguard town hall stops, nowhere else on the route does as far as I know. It is some time since I was last in Haverfordwest, but the LED signs in Fishguard have very little space for anything other than the service number, due time and final destination. The kind of large LED sign you get at railways stations, listing all the calling points, is a bit too big to put at many bus stops.

If you mean on-board information, 1. that is already too late if you have boarded the wrong bus and 2. not all the vehicles used on the T5 are equipped with 'next stop' computer screens. The 7 Optare Tempos are equiped, but the last time I saw most of those the computer was just displaying an error message. The one screen I did see working hadn't been updated, so did not include New Quay on the X50 service (maybe they have now it is the T5). Even when it is all working, it only shows the next handful of stops, not a variation a long way down the route. I'm also not sure if the route loaded on the computer is determined based on the route number displayed outside the bus, or if it can cope with variations which do not have their own number.

 

[quarella]

The TrawsCymru T5 (which has now largely replaced the X50/550) has LED signs at Haverfordwest bus station and Fishguard town hall stops, nowhere else on the route does as far as I know. It is some time since I was last in Haverfordwest, but the LED signs in Fishguard have very little space for anything other than the service number, due time and final destination. The kind of large LED sign you get at railways stations, listing all the calling points, is a bit too big to put at many bus stops.

If you mean on-board information, 1. that is already too late if you have boarded the wrong bus and 2. not all the vehicles used on the T5 are equipped with 'next stop' computer screens. The 7 Optare Tempos are equiped, but the last time I saw most of those the computer was just displaying an error message. The one screen I did see working hadn't been updated, so did not include New Quay on the X50 service (maybe they have now it is the T5). Even when it is all working, it only shows the next handful of stops, not a variation a long way down the route. I'm also not sure if the route loaded on the computer is determined based on the route number displayed outside the bus, or if it can cope with variations which do not have their own number.

I realise bus stop displays are few and far between and limited in information displayed although can be read in conjunction with other information such as a timetable. THey may not show as much as a railway station screen but even with those, station announcements, on train announcements both automated and by train crew passengers still manage to board the wrong train, and stay on it sometimes for a number of hours!

I hadn't thought about onboard displays are they are still relatively rare. I am no expert but I cannot see a problem in making a system able to cope with route variations.

What I was getting at was - On the front of the bus. Usually above the windscren the route number is displayed and the destination. On a blind this may just be the destination or possibly one via point but on the electronice LED displays on many bus services I see including some Traws Cymru that I regularly see there is a second line which scrolls through intermediate calling points.

 

[Teflon Lettuce]

To take an example from the London Underground.. The northern line. At the northern end of the line there are 3 branches ( Edgeware, High Barnet and Mill Hill East. There are also short workings to Golders Green. At the southern end there is one branch to Morden with some short workings to Stockwell. There are also 2 branches in the middle of the line one via Moorgate and one via Charing Cross...

If you assert that each variation should have a separate number then if LU ever numbered the lines and decided that the Northern line would be line one then you would end up with the following:

1 Morden-Edgeware via Charing X
1A Morden- Edgeware via Moorgate
1B Morden- High Barnet via Charing X
1c Morden- High Barnet via Moorgate
1D Morden- Mill Hill East via Charing X
1E Morden- Mill Hill East via Moorgate
1F Morden- Golders Green via Charing X
1G Morden- Golders Green via Moorgate
1H Stockwell- Edgeware via Charing X
1J Stockwell- Edgeware via Moorgate
1K Stockwell- High Barnet via Charing X
1L Stockwell- High Barnet via Moorgate
1M Stockwell- Mill Hill East via Charing X
1N Stockwell- Mill Hill East via Moorgate
1P Stockwell- Golders Green via Charing X
1R Stockwell- Golders Green via Moorgate

And thats before any other variations that may be instituted at a later date.

Even if the City branch was allocated route no 2 there would still be 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 2, 2A, 2B, 2C, 2D, 2E, 2F, 2G

Seriously why is it accepted that rail passengers can be trusted to understand that not all trains on a certain line call at all stations, yet it is assumed that bus passengers are too thick to understand the same idea?

 

[duncombec]

The discussion does seem to be going around in circles a little, but it is worth pointing out two examples from Stagecoach East Kent. I seem to remember the OP asked exactly what the purpose of a service number was - is the actual answer that it can mean different things in different situations?

Stagecoach East Kent is an ardent user of suffixes (in contrast to Arriva Kent & Surrey, who prefer different numbers), and many corridors will have different suffixes for variants. However, recently, service 16, which forms the 'direct' link between Canterbury and Folkestone, was converted to a Gold service. The 16A and 16B suffixes, that had previously been used for those journeys that served a different route in Hawkinge, were removed and the entire route now operates under the 16 number. Now, Hawkinge is a rather large estate in comparison to some places the route serves. Whilst not quite the distances the OP refers to, don't be fooled by the scale of the map! http://www.stagecoachbus.com/uploads/hawkingesep14web.pdf
The reason: now the buses use LED displays the variants can be displayed there.

The second example is that of the 4 and 6 group of services, marketed as the "Triangle" by virtue of serving the three towns of Canterbury, Whistable and Herne Bay, which on the map form a Triangle. The 'original' service operated every 15 minutes, with the 4 and 4A operating Anti-Clockwise (Whitstable first) and the 6 Clockwise (Herne Bay first), with alternate plain and A versions. The plain versions served the University of Kent and Beltinge, the A versions Greenhill. Sunday journeys, which conspired to serve both areas, were given a 'B' suffix: http://www.stagecoachbus.com/uploads/trianglenetworkmap010910kg_4b6bsunday.pdf
Later on, in response to the uptake of schoolchildren as a result of the KCC freedom pass, the 'X' variant was introduced, running between Canterbury and Herne Bay only, upping the frequency to every 10 minutes over that section. the 'X' demonstrated a restriction - not in stops, just that freedom pass holders were not allowed to travel.
Act three comes in the from of growing traffic and a decision to up the frequency to 10 minutes all the way around. The plain variants were withdrawn from the University but kept on serving Beltinge, the A versions kept on serving Greenhill, the B version stayed the same whilst the X versions served neither Beltinge nor Greenhill but the University instead. As far as I know, the freedom pass restriction was withdrawn, so there are now four variants: plain, A, B and.... X. The purpose for the 'X' has changed, but as it operated at the same times as the previous version on the original section, rather than renumber it (C, with a main variant coming after the Sunday oddity; or 'U', which brings back memories of the ancient vehicles on the University service before it received a huge upgrade and a massive increase in passengers), the number remained.
http://www.stagecoachbus.com/uploads/cwhnetworkmapkg010412[0].pdf; http://www.stagecoachbus.com/uploads/hernebaynetworkmap270114mm.pdf

So, is it as simple as the LED's? Does the fact lie in the 16 only having two variations (one way or the other in Hawkinge), whereas the 4/6 group have many, that wouldn't fit on one screen? Does it matter what the suffix is? Would it be better to have separate numbers (given that the first non-repeated number in Canterbury would be 19, and non repeated number at all 20, then 21, 24...) for all the variants and not bother with suffixes?

As others have suggested, I think we may be trying to shoehorn a size 5 onto a size 9 by suggesting there is a one-rule-fits-all.

 

[bussnapperwm]

The discussion does seem to be going around in circles a little, but it is worth pointing out two examples from Stagecoach East Kent. I seem to remember the OP asked exactly what the purpose of a service number was - is the actual answer that it can mean different things in different situations?

Stagecoach East Kent is an ardent user of suffixes (in contrast to Arriva Kent & Surrey, who prefer different numbers), and many corridors will have different suffixes for variants. However, recently, service 16, which forms the 'direct' link between Canterbury and Folkestone, was converted to a Gold service. The 16A and 16B suffixes, that had previously been used for those journeys that served a different route in Hawkinge, were removed and the entire route now operates under the 16 number. Now, Hawkinge is a rather large estate in comparison to some places the route serves. Whilst not quite the distances the OP refers to, don't be fooled by the scale of the map! http://www.stagecoachbus.com/uploads/hawkingesep14web.pdf
The reason: now the buses use LED displays the variants can be displayed there.

The second example is that of the 4 and 6 group of services, marketed as the "Triangle" by virtue of serving the three towns of Canterbury, Whistable and Herne Bay, which on the map form a Triangle. The 'original' service operated every 15 minutes, with the 4 and 4A operating Anti-Clockwise (Whitstable first) and the 6 Clockwise (Herne Bay first), with alternate plain and A versions. The plain versions served the University of Kent and Beltinge, the A versions Greenhill. Sunday journeys, which conspired to serve both areas, were given a 'B' suffix: http://www.stagecoachbus.com/uploads/trianglenetworkmap010910kg_4b6bsunday.pdf
Later on, in response to the uptake of schoolchildren as a result of the KCC freedom pass, the 'X' variant was introduced, running between Canterbury and Herne Bay only, upping the frequency to every 10 minutes over that section. the 'X' demonstrated a restriction - not in stops, just that freedom pass holders were not allowed to travel.
Act three comes in the from of growing traffic and a decision to up the frequency to 10 minutes all the way around. The plain variants were withdrawn from the University but kept on serving Beltinge, the A versions kept on serving Greenhill, the B version stayed the same whilst the X versions served neither Beltinge nor Greenhill but the University instead. As far as I know, the freedom pass restriction was withdrawn, so there are now four variants: plain, A, B and.... X. The purpose for the 'X' has changed, but as it operated at the same times as the previous version on the original section, rather than renumber it (C, with a main variant coming after the Sunday oddity; or 'U', which brings back memories of the ancient vehicles on the University service before it received a huge upgrade and a massive increase in passengers), the number remained.
http://www.stagecoachbus.com/uploads/cwhnetworkmapkg010412[0].pdf; http://www.stagecoachbus.com/uploads/hernebaynetworkmap270114mm.pdf

So, is it as simple as the LED's? Does the fact lie in the 16 only having two variations (one way or the other in Hawkinge), whereas the 4/6 group have many, that wouldn't fit on one screen? Does it matter what the suffix is? Would it be better to have separate numbers (given that the first non-repeated number in Canterbury would be 19, and non repeated number at all 20, then 21, 24...) for all the variants and not bother with suffixes?

As others have suggested, I think we may be trying to shoehorn a size 5 onto a size 9 by suggesting there is a one-rule-fits-all.

The madness with variants on another route out of Canterbury

13 Canterbury to Walmer via Sandwich
13A Canterbury to Sandwich
13A Canterbury to Deal via Sandwich (AM M-F)
13A Canterbury to Walmer via Sandwich (SuO and 1645 M-Sa Ex Walmer)
13A Sandwich to Whitfield (Thanet allocation last I checked - SchO)
13A Sandwich to Deal via Bettshanger (SchO - Dover Duty IIRC))
13A Walmer to Canterbury via Dover Road/The Strand in Walmer (0649 ex Walmer M-SaO)

 

[duncombec]

The madness with variants on another route out of Canterbury

13 Canterbury to Walmer via Sandwich
13A Canterbury to Sandwich
13A Canterbury to Deal via Sandwich (AM M-F)
13A Canterbury to Walmer via Sandwich (SuO and 1645 M-Sa Ex Walmer)
13A Sandwich to Whitfield (Thanet allocation last I checked - SchO)
13A Sandwich to Deal via Bettshanger (SchO - Dover Duty IIRC))
13A Walmer to Canterbury via Dover Road/The Strand in Walmer (0649 ex Walmer M-SaO)

Quite, although here (as with parallel route 14), the suffixes are used to differentiate between routings in Staple and Ash, rather than ultimate destinations. I think you have identified there that we'd be up to 13F... not very customer friendly! (Heaven forbid were they to decide the 13/14 were all one corridor!) The 15 group is similar, where 15's serve St Mary's Bay, 15As do not but serve St Mary's Bay, and 15Bs serve River (a bit they took over from the 60 when developer funding ran out). By the time you get through the route variations there we'll have something looking like Teflon Lettuce's underground scheme!