Differences between class 320/3 and 320/4

[Bill57p9]

I have been looking up some reference information in the Scottish Sectional Appendix and noticed differences in the route clearances between subclasses 320/3 and 320/4.
In some cases class 321s - of course which the class 320/4s were converted from - are different from 320/4
For example:

Route	320/3	320/4	321	322
WCML Gretna Junction - Law Jn	Permitted	Prohibited Gretna Jn - Carstairs	Prohibited Carstairs Plat 2	Permitted
WCML Lesmahago Jn - Polmadie Jn	Permitted	Permitted	ECS only	Permitted
Carstairs, Station Jn - East Jn	Permitted	Not cleared	Not cleared	Permitted
Holytown Jn - Mossend East Jn - Uddingston Jn	Permitted	Permitted	Not cleared	Permitted
Wishaw Central Jn - Shieldmuir Jn	Permitted	Not cleared	Not cleared	Permitted
Larkhall Branch	Not cleared	Permitted	Not cleared	Not cleared
Ayr line, Cook St Jn - Ayr	Permitted	Permitted	Not cleared	Permitted

What are the differences between 320/3 and 320/4. Or even 320/4s and 321 or 322 other than 3 vs 4 car - also 321 vs 322? Or is this purely historical of when types were cleared? For example many years ago 321/9s operated Haymarket to North Berwick but were allocated to Shields Road EMUD and therefore would require access.

 

[Kite159]

For example many years ago 321/9s operated Haymarket to North Berwick but were allocated to Shields Road EMUD and therefore would require access.

Wasn't it the 322s which were in Scotland, the 3x 321/9s being based in West Yorkshire for their life [until heading to Greater Anglia]?

As for the difference between a 320/3 & 320/4 might be down to the former 321s being 100mph units whereas the original /3 units being 90mph max?

 

[Falcon1200]

The differing restrictions for 320/3 and 320/4, which are essentially the same thing, are bizarre! They mean that a 320/4 cannot work the Lanark route, and a 320/3 cannot go to Larkhall. However; 320318, along with 318267, is working 2L06 1847 Dalmuir-Larkhall today, so the table is somehow wrong.

 

[norbitonflyer]

Wasn't it the 322s which were in Scotland, the 3x 321/9s being based in West Yorkshire for their life [until heading to Greater Anglia]?

The 322s started on the Stansted Express. After refurbished 317s took over that route, they became common-user in WAGN. In 1998 two were subleased to First North Western for a short-lived Euston-Manchester Airport service. In 2001 they went to Scotrail to work the North Berwick Line, taking over from the slam door 305s. When that route was taken over by Class 90/Mark 3 push pull sets they went back in 2004 to what was by then "one" and then in 2005 back to North Berwick. In 2011 they went to Northern to work alongside the 321/9s, and in 2020 back to Greater Anglia where they stayed until withdrawal in 2022

 

[Bill57p9]

Wasn't it the 322s which were in Scotland, the 3x 321/9s being based in West Yorkshire for their life [until heading to Greater Anglia]?

As for the difference between a 320/3 & 320/4 might be down to the former 321s being 100mph units whereas the original /3 units being 90mph max?

You could well be right about the 321/9s.

The 320s originally had a top speed of 75mph but were retrofitted with yaw dampers to permit 90mph running for the WCML to Lanark and Carstairs. Are the 320/4s limited to 90 or 100mph?

 

[AlistairCowell]

Class 320/4 has 100mph max speed.

Another main difference between Class 320/3 and 320/4 is the window right next to the accessible toilet. Class 320/3 has a large window that overlaps into the toilet area, while the Class 320/4 has a small window, which Class 321 and 322 units also have.

I think the Class 320/3s were the first to be fitted with accessible toilets and the reason there was an overlap window might be to do with last minute adjustments or that there might have been no small window frames available at the time.

 

[Bikeman78]

The differing restrictions for 320/3 and 320/4, which are essentially the same thing, are bizarre! They mean that a 320/4 cannot work the Lanark route, and a 320/3 cannot go to Larkhall. However; 320318, along with 318267, is working 2L06 1847 Dalmuir-Larkhall today, so the table is somehow wrong.

Four 320/4 went to Lanark yesterday. 318, 320/3 and 320/4 appear to be treated as one fleet now.

 

[Strathclyder]

Four 320/4 went to Lanark yesterday. 318, 320/3 and 320/4 appear to be treated as one fleet now.

Yes indeed, this has been the case since the 320/3s had yaw dampers fitted in 2010/11, brought about as part of the 380 rollout and the Airdrie-Bathgate reopening requiring the bulk of the 334 fleet. Was more about increasing fleet flexibilty post-A+B reopening than allowing 320s to run on the WCML Argyle Line services at 90mph; timings are still 75mph for those services anyway.

Externally, the main visual difference between the two 320 variants is the size of the LED display in the cab. Otherwise, the average passenger would be hard-pressed telling the difference.

 

[Falcon1200]

Four 320/4 went to Lanark yesterday. 318, 320/3 and 320/4 appear to be treated as one fleet now.

Indeed, on the non-380 diagrams to Neilston any of the 3 variants can turn up, and sometimes two together!

 

[Bill57p9]

Thank you to everyone for their responses.

I have had a quick look at RTT for the Lanark services: some paths are timed for 75mph, others for 100mph. Indeed some Glasgow to Lanark services are timed for 75mph with their returns times for 100mph.

I can only conclude that the operation on the ground appears to treat the 318, 320/3 and 320/4 as a single interoperable fleet with diagrams timed for 75mph, despite differences in top speed and the clearances stated in the sectional appendix.

Out of sheer curiosity, if a mixed type train is being operated (e.g. 320/3 + 320/4) does the tight lock multiple working auto negotiate and limit max speed to the lowest rated unit or does it rely on the driver?
(I do recall in another thread discussions around over speeding pacers when multiple working with faster DMUs)

 

[_toommm_]

Out of sheer curiosity, if a mixed type train is being operated (e.g. 320/3 + 320/4) does the tight lock multiple working auto negotiate and limit max speed to the lowest rated unit or does it rely on the driver?

It's down to the driver to know what their consist is, the couplers aren't smart enough to limit the speed. I can only think of that applying to a 158+170 (90mph+100mph respectively) consist, I'm not au-fait with the 320s.

 

[D365]

There is no electronic logic in the BSI or Tightlock couplers. Nor is there any sort of speed limit facility built into their respective multiple working systems.

 

[TT-ONR-NRN]

Class 320/4 has 100mph max speed.

Another main difference between Class 320/3 and 320/4 is the window right next to the accessible toilet. Class 320/3 has a large window that overlaps into the toilet area, while the Class 320/4 has a small window, which Class 321 and 322 units also have.

I think the Class 320/3s were the first to be fitted with accessible toilets and the reason there was an overlap window might be to do with last minute adjustments or that there might have been no small window frames available at the time.

Another difference, not really a notable one but one all the same, is the PIS.
The 320/3 have the (IMO very classy) PIS and font as found on the 357, 375, 376 and 377/5 (Southern have recently replaced the font on 377/1-4, to my dismay), while 320/4 have a very cheap looking thing that I believe was also fitted to the 456s and a handful of 321s (most had the same as 317s instead)

 

[craigybagel]

Thank you to everyone for their responses.

I have had a quick look at RTT for the Lanark services: some paths are timed for 75mph, others for 100mph. Indeed some Glasgow to Lanark services are timed for 75mph with their returns times for 100mph.

I can only conclude that the operation on the ground appears to treat the 318, 320/3 and 320/4 as a single interoperable fleet with diagrams timed for 75mph, despite differences in top speed and the clearances stated in the sectional appendix.

Out of sheer curiosity, if a mixed type train is being operated (e.g. 320/3 + 320/4) does the tight lock multiple working auto negotiate and limit max speed to the lowest rated unit or does it rely on the driver?
(I do recall in another thread discussions around over speeding pacers when multiple working with faster DMUs)

I suspect it's all rather moot, as opportunities for 320s to run above 90mph are extremely limited, but there won't be any limiter. In fact.....

There is no electronic logic in the BSI or Tightlock couplers. Nor is there any sort of speed limit facility built into their respective multiple working systems.

.... Do 80s/90s BR designed EMUs even have limiters fitted? The DMUs from the same era certainly don't.