Most contraventions of bus gates are brought as a moving traffic contravention, usually 33E: Using a route restricted to certain vehicles - buses, cycles and taxis only. Cumberland Road's blue roundel shows a bus, a cycle, a solo motorcycle and the word "taxi". Its technical reference is diagram 953B.
If you look at a list of contravention codes, you will see that there isn't one for buses, cycles, taxis and solo motorcycles. That's because civil enforcement of moving traffic contraventions outside London is restricted to traffic orders for which local authorities have used signs listed in Table A in paragraph 8A of Schedule 7 of Traffic Management Act 2004.
Diagram 953B is not included, so local authorities use a bus lane contravention instead. Paragraph 6 of Schedule 7 of Traffic Management Act 2004 defines a bus lane contravention as:
6 (1) A bus lane contravention is a contravention of any provision of a traffic order relating to the use of an area of road that is or forms part of a bus lane.
(2) An area of road is or forms part of a bus lane if the order provides that it may be used—
(a) only by buses (or a particular description of bus), or
(b) only by buses (or a particular description of bus) and some other class or classes of vehicular traffic.
This means that a bus gate is legally a bus lane for the purposes of civil enforcement. Local authorities therefore allege contravention code 34: Being in a bus lane.
except for the purpose of crossing .
As the Cumberland Road bus gate is 4m x 4m and many vehicles are more than 4m long, that raises the question of whether such a vehicle is ever "in" the Cumberland Road bus lane. The Shorter Oxford English Dictionary (6th edition) defines the preposition "in" as:
I Of position and location.
1 Within the limits or bounds of; within. b With names of towns having public or private importance.
2 Referring to non-physical things treated as having extension or content.
3 In relation to; in the context of; as a member of.
4 Expr. relation to a garment, covering, etc., which envelops or is worn
5 On (with ref. to position). Long rare exc. Scot.
6 (obsolete) Among
7 Defining the part of something affected
8 With numbers, nouns of quantity, etc.: as a proportionate part of
Of these, the first is the only one which is meaningful in the context. At no time is a vehicle which is longer than 4m within the limits or boundary of the Cumberland Road bus lane.
Bus gate is in essence a short contraflow bus lane. Chapter 3 of TSM shows in Figures 9-14 and 9-15 the signage at a T junction where a contraflow bus lane starts. Paragraph 9.4.5 says:
9.4.5 The start of the contraflow lane should be separated from opposing traffic by a refuge in the centre of the road. The exit side of the road, used by all traffic, should be protected by “no entry” signs to diagram 616 (S3‑2‑10) as for ordinary one‑way roads. Where a bollard is provided on the refuge, this may include a “no entry” sign, but a full‑size sign should also be provided. A contraflow bus lane may be signed by either the appropriate version of diagram 953 (S3‑2‑33, see Figure 9-16) as shown in Figure 9-14 or the “no entry” sign to diagram 616 as shown in Figure 9-15. Where diagram 953 is used, the variant showing both the bus and cycle symbols should be used where pedal cycles are permitted to use the lane. The legend “local” on the bus symbol indicates that the lane may be used only by those buses operating a local service as defined in Schedule 1. In Figure 9-14, one “no entry” sign may be used instead of two. Where the “no entry” sign is used as shown in Figure 9-15, two “no entry” signs may be used instead of three. Only the sign on the left hand side of the road has a supplementary plate; this will have one of the following legends as appropriate:
“Except” and—
a) “buses” or “local buses”;
b) “buses and cycles” or “buses & cycles”; or
c) “local buses and cycles” or “local buses & cycles”.
9.4.6. It is for the traffic authority to determine whether to use diagram 953 or the “no entry” sign, bearing in mind that the aim should be to provide consistent signing within a particular area. The “no entry” sign is likely to be appropriate where a central refuge cannot be provided at the start of the bus lane. In this case, the “Except buses” plate or its appropriate variant, should be used only with the sign on the left hand side of the road (similar to a road with a central refuge as shown in Figure 9-15). It should be noted that the “Only” plate, previously used with diagram 953, is no longer prescribed by the Regulations. “End of bus lane” signs to diagram 964 (S9‑4‑11) are not used with contraflow lanes, nor are time plates, as these lanes operate continuously.
The Traffic Signs Manual thus does provide guidance as to what to do when the central refuge is placed beyond the junction: it is to put No Entry signs on each side of the road with that on the left having an Except plate which specifies the types of vehicle which are permitted. As far as DfT are concerned, it goes without saying that the bus restriction applies from the junction rather than starting further on.