I have been putting together some of the wiki pages on warning signs and was wondering if anyone can help with the dates of what was changed or added to TSRGD after 1964.

Such as when did the junction signs change to show priorities.
And the same for the merge signs - I know this was slightly later since the 1978 Highway Code shows the new junction sign but old merge ones.

And new warnings that have been added, toads, wildfoul, tractors, queues likely, slow lorries etc.
When did the snowflake sign for ice and snow replace the worded versions, it appears in the 96 HC but isn't shown in the 93 version?

I think it's pretty much any diagram with a decimal fraction in its number, or 582 and higher.

At a guess:

* Junction signs started showing priorities with TSRGD 1975.

* The modern merge signs date from TSRGD 1981. (Lane closures used to be indicated on a triangular warning sign. I think either TSRGD 1981 or 1994 put an end to this approach.)

* Most of the new symbolic warning signs were introduced in TSRGD 1994.

The current diagram numbering scheme is not original. The original scheme was based on the same concept of assigning a number range to a given sign type, but the assignments were different, with directional informatory signs (present-day 2000 series) having diagram numbers in the 800s. I think the current diagram numbering scheme was introduced in TSRGD 1994, but I am not sure. Prior to TSRGD 1994, working drawings for traffic signs were in a WBM series where drawing numbers did not correspond to TSRGD diagram numbers; after TSRGD 1994 came out, the working drawings were reissued with the TSRGD diagram number being also the drawing number.