Traffic Signs Manual Chapter 3 explains the requirements for RPZs clearly, but the actual law is in TSRGD:
RPZ entrance signs are covered by S5-3-2 on page 98 of TSRGD. This requires them only to be used for a “Restricted Parking Zone”, a term which is defined in Schedule 1 on page 30. Clause (b) of this definition requires that “none of the road markings at items 1 to 4 of the signs table in Part 4 of Schedule 7 has been placed.” These S7-4 markings it refers to are single and double yellow lines and ‘kerb blips’. Hence, it’s not legally an RPZ if you do have yellow lines in it and therefore it was not legal to place the RPZ entrance signs for it.
I wondered if someone would clarify an issue concerning markings within a restricted parking zone. We have a situation where there is a short section of road which forms part of a public realm scheme and is a restricted parking zone with an abundance of repeater signs. The same ‘no waiting at any time’ restriction applies either side of the zone and there are double yellow lines marked. However, for whatever reason, the zone entry sign has been positioned in a section of the road where there are yellow lines marked. We have recently lost a case where a motorist was parked within the RPZ but was confused as he thought the restriction ended where the markings stopped. The adjudicator made a comment about it being clear in the TRSGD that lines were not permitted within a RPZ. If so, please would someone direct me to the relevant section. I believe the entry sign needs to be repositioned but I have been asked to clarify the issue with a view to appealing the decision.